Cell Structure & Function

Topic: Endomembrane System; Subtopic: Golgi Apparatus

Keyword Definitions:

• Golgi Apparatus: A cell organelle responsible for modification, packaging, and transport of materials synthesized in the endoplasmic reticulum.

• Endoplasmic Reticulum (ER): A network of membranous tubules involved in synthesis of proteins (RER) and lipids (SER).

• Vesicles: Small membrane-bound sacs that transport materials between organelles.

• Cis Face: The receiving side of the Golgi body facing the ER.

• Trans Face: The shipping side of the Golgi from which vesicles bud off to other destinations.

Lead Question – 2025

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A): The primary function of the Golgi apparatus is to package the materials made by the endoplasmic reticulum and deliver it to intracellular targets and outside the cell.
Reason (R): Vesicles containing materials made by the endoplasmic reticulum fuse with the cis face of the Golgi apparatus, and they are modified and released from the trans face of the Golgi apparatus.

In the light of the above statements, choose the correct answer from the options given below:
(1) Both A and R are true and R is the correct explanation of A
(2) Both A and R are true but R is not the correct explanation of A
(3) A is true but R is false
(4) A is false but R is true

Explanation: The Golgi apparatus modifies, sorts, and packages materials synthesized by the endoplasmic reticulum. Vesicles from the ER fuse with the cis face, move through cisternae, and are released from the trans face after modification. Hence, both statements are true and R correctly explains A. The correct answer is (1) Both A and R are true and R is the correct explanation of A.

Guessed Questions

1. Which of the following organelles is involved in packaging and secretion of materials in the cell?
(1) Lysosome
(2) Golgi apparatus
(3) Ribosome
(4) Nucleus
Explanation: The Golgi apparatus modifies, packages, and secretes proteins and lipids synthesized in the ER. It forms secretory vesicles that transport materials to various destinations. Hence, the correct answer is (2) Golgi apparatus.

2. Which face of the Golgi apparatus receives vesicles from the endoplasmic reticulum?
(1) Trans face
(2) Cis face
(3) Lateral face
(4) Median face
Explanation: The cis face of the Golgi apparatus faces the endoplasmic reticulum and receives transport vesicles containing synthesized materials. These materials are further processed as they move toward the trans face. Hence, the correct answer is (2) Cis face.

3. The Golgi apparatus was discovered by:
(1) Camillo Golgi
(2) Robert Hooke
(3) Matthias Schleiden
(4) Rudolf Virchow
Explanation: The Golgi apparatus was first observed by Italian scientist Camillo Golgi in 1898 using a silver staining technique. It is named after him and plays a vital role in secretion and intracellular transport. Hence, the correct answer is (1) Camillo Golgi.

4. Which of the following structures originates from the Golgi apparatus?
(1) Lysosomes
(2) Ribosomes
(3) Peroxisomes
(4) Mitochondria
Explanation: Lysosomes are membrane-bound vesicles formed from the Golgi apparatus containing hydrolytic enzymes. These enzymes digest worn-out organelles and macromolecules. Hence, the correct answer is (1) Lysosomes.

5. Golgi apparatus is most abundant in cells involved in:
(1) Photosynthesis
(2) Secretion
(3) Conduction
(4) Storage
Explanation: Cells involved in secretion such as glandular and plasma cells have well-developed Golgi apparatus. It processes and packages proteins or hormones for secretion. Hence, the correct answer is (2) Secretion.

6. The Golgi apparatus is absent in:
(1) Bacterial cells
(2) Plant cells
(3) Fungal cells
(4) Animal cells
Explanation: Golgi apparatus is a membrane-bound organelle found only in eukaryotic cells. Prokaryotic cells like bacteria lack it because they have no membrane-bound organelles. Hence, the correct answer is (1) Bacterial cells.

7. Matching Type:
List I – Function
A. Formation of lysosomes
B. Packaging of enzymes
C. Secretion of hormones
D. Synthesis of lipids

List II – Organelle
I. Golgi apparatus
II. Endoplasmic reticulum
III. Ribosome
IV. Nucleus

(1) A–I, B–I, C–I, D–II
(2) A–II, B–III, C–IV, D–I
(3) A–III, B–IV, C–II, D–I
(4) A–IV, B–I, C–III, D–II
Explanation: Golgi apparatus forms lysosomes, packages enzymes, and aids in hormone secretion, whereas lipid synthesis occurs in the smooth endoplasmic reticulum. Hence, the correct answer is (1) A–I, B–I, C–I, D–II.

8. Fill in the Blanks:
The side of the Golgi apparatus facing the endoplasmic reticulum is called the ______ face.
(1) Cis
(2) Trans
(3) Lateral
(4) Median
Explanation: The Golgi apparatus has two poles – the cis face (receiving side) and the trans face (shipping side). The cis face receives vesicles from the endoplasmic reticulum. Hence, the correct answer is (1) Cis.

9. Assertion–Reason Type:
Assertion (A): Golgi apparatus plays a key role in cell wall formation in plant cells.
Reason (R): It is involved in secretion of polysaccharides and pectins used in the cell wall.
(1) Both A and R are true and R explains A
(2) Both A and R are true but R does not explain A
(3) A is true but R is false
(4) A is false but R is true
Explanation: In plant cells, the Golgi apparatus secretes pectins and polysaccharides used in forming cell wall components. Hence, both statements are true, and R explains A. The correct answer is (1) Both A and R are true and R explains A.

10. Choose the Correct Statements:
Statement I: The Golgi apparatus is involved in glycosylation of proteins.
Statement II: The Golgi apparatus synthesizes DNA and RNA.
(1) Both statements are correct
(2) Both statements are incorrect
(3) Statement I correct, Statement II incorrect
(4) Statement I incorrect, Statement II correct
Explanation: Golgi apparatus modifies proteins by glycosylation and lipids by glycosidation but does not synthesize DNA or RNA, which is a function of the nucleus. Hence, the correct answer is (3) Statement I correct, Statement II incorrect.

Topic: Prokaryotic Cell; Subtopic: Mesosome and its Functions

Keyword Definitions:

• Mesosome: A membranous infolding of the plasma membrane in prokaryotes, involved in cell wall formation, DNA replication, and respiration.

• Prokaryotic Cell: A cell lacking a true nucleus and membrane-bound organelles.

• Chromatophores: Pigmented membrane structures in photosynthetic bacteria that perform photosynthesis.

• Cristae: Infoldings of the inner mitochondrial membrane found in eukaryotic cells, increasing surface area for respiration.

• Endoplasmic Reticulum: A eukaryotic membrane network responsible for protein and lipid synthesis.

Lead Question – 2025

A specialised membranous structure in a prokaryotic cell which helps in cell wall formation, DNA replication and respiration is

(1) Mesosome

(2) Chromatophores

(3) Cristae

(4) Endoplasmic Reticulum

Explanation:

Mesosomes are folded invaginations of the plasma membrane in prokaryotic cells. They increase the surface area for enzymatic activities and assist in DNA replication, distribution to daughter cells, and cell wall formation during division. They also function in respiration, similar to mitochondria in eukaryotes. Thus, the correct answer is Mesosome.

Guessed Questions:

1. The infoldings of the plasma membrane in prokaryotes that perform functions similar to mitochondria are called

(1) Mesosomes

(2) Ribosomes

(3) Lysosomes

(4) Nucleoid

2. Which structure in a prokaryotic cell is involved in respiratory enzyme activity?

(1) Mesosome

(2) Ribosome

(3) Capsule

(4) Flagellum

3. The site of DNA attachment during bacterial cell division is

(1) Mesosome

(2) Ribosome

(3) Plasmid

(4) Cell wall

4. Which of the following is absent in prokaryotic cells?

(1) Mitochondria

(2) Mesosome

(3) Ribosome

(4) Plasma membrane

5. The respiratory enzymes in prokaryotic cells are located in the

(1) Mesosomes

(2) Ribosomes

(3) Golgi bodies

(4) Cytoplasm

6. In bacteria, mesosomes are the extensions of

(1) Plasma membrane

(2) Cell wall

(3) Nucleoid

(4) Cytoplasm

Assertion – Reason Question

7. Assertion (A): Mesosomes are the sites of aerobic respiration in prokaryotes.

Reason (R): Mitochondria are absent in prokaryotic cells.

(1) Both A and R are true and R is the correct explanation of A

(2) Both A and R are true but R is not the correct explanation of A

(3) A is true but R is false

(4) A is false but R is true

Matching Type Question

8. Match the following:

List I (Structure) — List II (Function)

A. Mesosome — 1. Photosynthesis

B. Chromatophore — 2. Respiration

C. Ribosome — 3. Protein synthesis

D. Plasmid — 4. Extra-chromosomal DNA

(1) A–2, B–1, C–3, D–4

(2) A–1, B–3, C–2, D–4

(3) A–3, B–2, C–1, D–4

(4) A–4, B–1, C–3, D–2

Fill in the Blanks / Completion Question

9. In prokaryotic cells, respiratory enzymes are located on __________.

(1) Mesosomes

(2) Endoplasmic reticulum

(3) Cristae

(4) Thylakoids

Choose the Correct Statements Question

10. Statement I: Mesosomes are involved in bacterial respiration.

Statement II: Mesosomes are absent in eukaryotic cells.

(1) Both statements are true

(2) Both statements are false

(3) Statement I is true, Statement II is false

(4) Statement I is false, Statement II is true

Explanation:

Mesosomes are plasma membrane infoldings present only in prokaryotic cells, not eukaryotes. They play important roles in cell wall formation, DNA replication, and respiration. Eukaryotic cells use mitochondria for respiration instead. Therefore, both statements I and II are true, and the correct option is (1). 

Topic: Cell Organelles and their Functions; Subtopic: Structure and Role of Cell Components

Keyword Definitions:
• Centromere: A region on a chromosome that holds sister chromatids together and attaches to spindle fibres during cell division.
• Cilium: A short, hair-like structure aiding in movement and transport across cell surfaces.
• Cristae: Folded inner membrane of mitochondria increasing surface area for ATP synthesis.
• Cell Membrane: Semi-permeable phospholipid bilayer controlling the movement of substances in and out of cells.

Lead Question – 2025
Match List-I with List-II
List-I                                      List-II
A. Centromere                              I. Mitochondrion
B. Cilium                                        II. Cell division
C. Cristae                                        III. Cell movement
D. Cell membrane                       IV. Phospholipid Bilayer
Choose the correct answer from the options given below:
(1) A-I, B-II, C-III, D-IV
(2) A-II, B-I, C-IV, D-III
(3) A-IV, B-II, C-III, D-I
(4) A-II, B-III, C-I, D-IV

Explanation: The centromere helps in cell division (II), cilium is involved in cell movement (III), cristae are inner mitochondrial folds (I), and the cell membrane is a phospholipid bilayer (IV). Thus, the correct match is A–II, B–III, C–I, D–IV. This arrangement reflects each organelle’s major role. Answer: (4).

1. Which cell organelle is known as the “powerhouse of the cell”?
(1) Ribosome
(2) Nucleus
(3) Mitochondrion
(4) Golgi apparatus

Explanation: Mitochondria are termed the “powerhouse of the cell” because they generate energy in the form of ATP through oxidative phosphorylation. Their inner folds, called cristae, contain enzymes for respiration. They play a crucial role in energy metabolism. Hence, the correct answer is (3) Mitochondrion.

2. The cell organelle responsible for packaging and secretion is:
(1) Endoplasmic reticulum
(2) Golgi apparatus
(3) Ribosome
(4) Lysosome

Explanation: The Golgi apparatus modifies, packages, and transports materials synthesized in the endoplasmic reticulum. It forms secretory vesicles and lysosomes. It is essential for protein processing and transport. Therefore, the correct answer is (2) Golgi apparatus.

3. Which of the following organelles is involved in protein synthesis?
(1) Ribosome
(2) Lysosome
(3) Peroxisome
(4) Golgi body

Explanation: Ribosomes are the molecular machines responsible for protein synthesis. They translate mRNA into polypeptide chains by linking amino acids together. Found freely or attached to rough ER, they play a key role in gene expression. The correct answer is (1) Ribosome.

4. Lysosomes are called “suicidal bags” because they:
(1) Produce energy
(2) Contain hydrolytic enzymes
(3) Synthesize proteins
(4) Form the plasma membrane

Explanation: Lysosomes contain hydrolytic enzymes that digest worn-out organelles and foreign materials. In case of cell damage, they rupture and release enzymes, causing self-digestion (autolysis). Hence, they are known as suicidal bags. The correct answer is (2) Contain hydrolytic enzymes.

5. Which organelle is absent in prokaryotic cells?
(1) Ribosome
(2) Nucleolus
(3) Cell wall
(4) Plasma membrane

Explanation: Prokaryotes lack membrane-bound organelles like the nucleus, mitochondria, and nucleolus. Ribosomes and the cell wall are present. Therefore, the nucleolus, being a nuclear structure, is absent in prokaryotes. Hence, the correct answer is (2) Nucleolus.

6. Smooth endoplasmic reticulum (SER) is mainly involved in:
(1) Protein synthesis
(2) Lipid metabolism
(3) DNA replication
(4) ATP synthesis

Explanation: The smooth endoplasmic reticulum synthesizes lipids, phospholipids, and steroids. It also helps in detoxification of drugs and poisons. Unlike rough ER, it lacks ribosomes. Thus, the correct answer is (2) Lipid metabolism.

7. Assertion–Reason:
Assertion (A): Centriole plays an essential role in spindle formation during cell division.
Reason (R): Centriole helps in chromosome movement by forming spindle fibres.
(1) Both A and R are true, and R correctly explains A.
(2) Both A and R are true, but R does not explain A.
(3) A is true, R is false.
(4) A is false, R is true.

Explanation: Centrioles organize microtubules into spindle fibres that attach to chromosomes during cell division, ensuring proper segregation. Thus, both statements are true, and R correctly explains A. Answer: (1).

8. Matching Type Question:
Match the following:
A. Ribosome → (i) Protein synthesis
B. Golgi apparatus → (ii) Packaging and secretion
C. Lysosome → (iii) Intracellular digestion
(1) A–i, B–ii, C–iii
(2) A–ii, B–i, C–iii
(3) A–iii, B–ii, C–i
(4) A–i, B–iii, C–ii

Explanation: Ribosomes synthesize proteins, the Golgi apparatus packages them for transport, and lysosomes digest unwanted materials. Hence, the correct match is A–i, B–ii, C–iii. Answer: (1).

9. Fill in the Blanks:
_________ controls all cellular activities and contains hereditary information.
(1) Nucleus
(2) Ribosome
(3) Mitochondria
(4) Golgi apparatus

Explanation: The nucleus serves as the control centre of the cell. It contains DNA, which stores genetic information for protein synthesis and regulation of cellular activities. Thus, the correct answer is (1) Nucleus.

10. Choose the Correct Statements:
Statement I: The cell membrane is selectively permeable.
Statement II: It allows all substances to pass freely.
(1) Only Statement I is correct.
(2) Only Statement II is correct.
(3) Both are correct.
(4) Both are incorrect.

Explanation: The plasma membrane allows selective passage of substances—some molecules diffuse freely, while others require carrier proteins. It prevents uncontrolled exchange. Thus, only statement I is correct. Answer: (1).

Topic: Ribosomes; Subtopic: Structure and Types of Ribosomes

Keyword Definitions:
• Ribosomes: Small cellular organelles responsible for protein synthesis.
• Prokaryotic Cells: Cells lacking a true nucleus and membrane-bound organelles.
• Eukaryotic Cells: Cells having a true nucleus and complex organelles.
• Svedberg Unit (S): A measure of sedimentation rate used to describe ribosome size and density.
• Subunits: Ribosomes consist of two unequal parts, large and small, that join during protein synthesis.

Lead Question – 2025
From the statements given below choose the correct option
A. The eukaryotic ribosomes are 80S and prokaryotic ribosomes are 70S.
B. Each ribosome has two sub-units.
C. The two sub-units of 80S ribosome are 60S and 40S while that of 70S are 50S and 30S.
D. The two sub-units of 80S ribosome are 60S and 20S and that of 70S are 50S and 20S.
E. The two sub-units of 80S are 60S and 30S and that of 70S are 50S and 30S.
(1) A, B, C are true (2) A, B, D are true (3) A, B, E are true (4) B, D, E are true

Explanation:
The eukaryotic ribosome is 80S, composed of 60S and 40S subunits, while the prokaryotic ribosome is 70S with 50S and 30S subunits. Each ribosome has two unequal parts that come together during protein synthesis. Hence, statements A, B, and C are correct. Therefore, the correct answer is (1) A, B, C are true.

Guessed Questions:

1. Single Correct Answer:
Ribosomes are also known as:
(1) Protein factories of the cell (2) Powerhouse of the cell (3) Suicide bags (4) Kitchen of the cell
Explanation:
Ribosomes are termed the protein factories of the cell as they synthesize proteins essential for cell structure and function. They read mRNA and link amino acids via peptide bonds. These ribosomes may be free in cytoplasm or attached to the endoplasmic reticulum. Hence, the correct answer is (1).

2. Single Correct Answer:
The 70S ribosome is found in:
(1) Mitochondria (2) Chloroplasts (3) Bacteria (4) Cytoplasm of eukaryotic cells
Explanation:
Prokaryotic organisms such as bacteria possess 70S ribosomes in their cytoplasm. Interestingly, mitochondria and chloroplasts of eukaryotic cells also contain 70S ribosomes, supporting the endosymbiotic theory of origin. These ribosomes synthesize proteins for organelle functions. Thus, the correct answer is (3) Bacteria.

3. Single Correct Answer:
Which of the following statements is correct about eukaryotic ribosomes?
(1) They are 70S type (2) They contain 60S and 40S subunits (3) They are free only in cytoplasm (4) Found only in nucleus
Explanation:
Eukaryotic ribosomes are 80S, composed of 60S and 40S subunits. They occur freely in cytoplasm or attached to the endoplasmic reticulum (RER). These ribosomes are crucial for protein synthesis in both structural and enzymatic proteins. Hence, the correct answer is (2) They contain 60S and 40S subunits.

4. Single Correct Answer:
Ribosomes are chemically composed of:
(1) RNA only (2) Proteins only (3) DNA and proteins (4) rRNA and proteins
Explanation:
Ribosomes are ribonucleoprotein complexes composed of ribosomal RNA (rRNA) and proteins. The rRNA provides structural stability and catalytic function, while the proteins aid in the assembly and maintenance of the ribosome. Therefore, the correct answer is (4) rRNA and proteins.

5. Single Correct Answer:
The ribosomes of mitochondria resemble those of:
(1) Eukaryotic cytoplasm (2) Bacteria (3) Fungi (4) Archaea
Explanation:
Mitochondrial ribosomes are 70S type, similar to bacterial ribosomes, supporting the endosymbiotic theory that mitochondria originated from free-living bacteria. This similarity explains mitochondrial semi-autonomy and its ability to synthesize some of its own proteins. Hence, the correct answer is (2) Bacteria.

6. Single Correct Answer:
Which of the following organelles lacks ribosomes?
(1) Mitochondria (2) Rough Endoplasmic Reticulum (3) Smooth Endoplasmic Reticulum (4) Chloroplast
Explanation:
Smooth Endoplasmic Reticulum (SER) lacks ribosomes on its surface. It is involved in lipid and steroid synthesis and detoxification processes, unlike RER which has ribosomes for protein synthesis. Thus, the correct answer is (3) Smooth Endoplasmic Reticulum.

7. Assertion–Reason Type:
Assertion (A): Ribosomes are the sites of protein synthesis.
Reason (R): Ribosomes read tRNA and attach amino acids to form polypeptide chains.
(1) Both A and R are true, and R is the correct explanation of A
(2) Both A and R are true, but R is not the correct explanation of A
(3) A is true, R is false
(4) A is false, R is true
Explanation:
Ribosomes are indeed the sites of protein synthesis, where tRNA brings amino acids that are joined into polypeptide chains. Thus, both statements are true, and R correctly explains A. Hence, the correct answer is (1).

8. Matching Type:
Match the following:
List I (Type) – List II (Location)
A. Free ribosomes – (i) Cytoplasm
B. Bound ribosomes – (ii) Endoplasmic Reticulum
C. 70S ribosomes – (iii) Prokaryotic cells
D. 80S ribosomes – (iv) Eukaryotic cytoplasm
(1) A-i, B-ii, C-iii, D-iv (2) A-ii, B-i, C-iii, D-iv (3) A-iv, B-iii, C-i, D-ii (4) A-i, B-iii, C-iv, D-ii
Explanation:
Free ribosomes occur in the cytoplasm, bound ribosomes on ER, 70S ribosomes in prokaryotes, and 80S in eukaryotic cytoplasm. Hence, the correct match is (1) A-i, B-ii, C-iii, D-iv.

9. Fill in the Blanks:
Ribosomes are attached to __________ endoplasmic reticulum to form RER.
(1) Smooth (2) Rough (3) Granular (4) None
Explanation:
Ribosomes attached to the surface of the endoplasmic reticulum form the Rough Endoplasmic Reticulum (RER). These ribosomes synthesize proteins that are transported out of the cell or used in membranes. Hence, the correct answer is (2) Rough.

10. Choose the Correct Statements:
Statement I: Ribosomes are membrane-bound organelles.
Statement II: Ribosomes can be free or attached to ER.
(1) Both statements are true (2) Both are false (3) I is false, II is true (4) I is true, II is false
Explanation:
Ribosomes are non-membranous structures that can either be free in cytoplasm or attached to ER. Hence, Statement I is false and Statement II is true. The correct answer is (3) I is false, II is true.

Topic: Cell Organelles; Subtopic: Golgi Apparatus

Keyword Definitions:
• Golgi Apparatus: A cell organelle that modifies, sorts, and packages proteins and lipids for secretion or use within the cell.
• Cis Face: The forming face of the Golgi body where materials arrive from the endoplasmic reticulum.
• Trans Face: The maturing face where processed materials leave the Golgi body.
• Cisternae: Flattened membrane-bound sacs forming the structure of the Golgi complex.
• Organelle: Specialized subunit within a cell with a specific function.

Lead Question - 2024 (Jhajjhar)

Given below are two statements:

Statement I: The Golgi cisternae are concentrically arranged near the nucleus with distinct convex cis or the forming face and concave trans or the maturing face.

Statement II: The cis and trans faces of the organelle are identical and interconnected.

In the light of the above statements, choose the correct answer from the options given below:
1. Both Statement I and Statement II are True.
2. Both Statement I and Statement II are False.
3. Statement I is True but Statement II is False.
4. Statement I is False but Statement II is True.

Explanation (Answer: 3. Statement I is True but Statement II is False):
The Golgi apparatus consists of flattened cisternae arranged near the nucleus, showing polarity with a convex cis face (forming) and a concave trans face (maturing). The cis and trans faces are functionally distinct and not identical; materials move directionally from the cis to trans side. This polarity ensures proper protein sorting and secretion.

1. The smooth endoplasmic reticulum is abundant in cells involved in:
1. Protein synthesis
2. Lipid metabolism
3. Chromosome segregation
4. Cell division

Explanation (Answer: 2. Lipid metabolism):
The smooth endoplasmic reticulum (SER) lacks ribosomes and is primarily associated with lipid and steroid synthesis, detoxification, and calcium storage. Cells such as liver hepatocytes and adrenal cortex cells have extensive SER. In contrast, rough ER with ribosomes is involved in protein synthesis and transport of secretory proteins.

2. The main function of lysosomes is:
1. Protein synthesis
2. Energy production
3. Intracellular digestion
4. Chromosome packaging

Explanation (Answer: 3. Intracellular digestion):
Lysosomes contain hydrolytic enzymes that digest worn-out cell organelles, macromolecules, and foreign substances. They maintain acidic pH for enzyme activity. These are formed by the Golgi apparatus and act as the cell’s “suicidal bags,” helping in autophagy and defense against invading pathogens by digesting them efficiently within the cell.

3. Which of the following organelles is known as the “powerhouse of the cell”?
1. Lysosome
2. Ribosome
3. Mitochondrion
4. Peroxisome

Explanation (Answer: 3. Mitochondrion):
Mitochondria produce ATP through oxidative phosphorylation, providing energy for cellular activities. They possess their own DNA and ribosomes, supporting the endosymbiotic theory. The inner membrane folds into cristae, increasing the surface area for energy production. Hence, mitochondria are termed the powerhouse of the cell for generating metabolic energy.

4. Ribosomes are composed of:
1. DNA and proteins
2. RNA and proteins
3. Lipids and carbohydrates
4. RNA and lipids

Explanation (Answer: 2. RNA and proteins):
Ribosomes consist of ribosomal RNA (rRNA) and proteins. They are the sites of protein synthesis and can be free in the cytoplasm or bound to the rough endoplasmic reticulum. The rRNA acts as a structural and catalytic component, forming large and small subunits that join during protein translation.

5. The nucleolus is mainly responsible for:
1. Lipid synthesis
2. Ribosomal RNA synthesis
3. DNA replication
4. ATP formation

Explanation (Answer: 2. Ribosomal RNA synthesis):
The nucleolus, located within the nucleus, synthesizes rRNA and assembles ribosomal subunits. It is rich in proteins and RNA. The rRNA genes on specific chromosomes (nucleolar organizer regions) are transcribed here. Ribosomal subunits then migrate to the cytoplasm, where they form functional ribosomes for protein synthesis.

6. Peroxisomes are involved in:
1. Photosynthesis
2. Lipid peroxidation
3. Detoxification and β-oxidation of fatty acids
4. Protein synthesis

Explanation (Answer: 3. Detoxification and β-oxidation of fatty acids):
Peroxisomes contain oxidative enzymes that degrade fatty acids via β-oxidation and detoxify hydrogen peroxide using catalase. They play vital roles in lipid metabolism and protection against oxidative stress. These organelles are abundant in liver and kidney cells, where they support cellular detoxification and metabolic regulation efficiently.

7. (Assertion-Reason Type)
Assertion (A): The mitochondria and chloroplasts are semi-autonomous organelles.
Reason (R): They contain their own DNA and ribosomes.
1. Both A and R are true, and R is the correct explanation of A.
2. Both A and R are true, but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Explanation (Answer: 1. Both A and R are true, and R is the correct explanation of A):
Mitochondria and chloroplasts possess circular DNA, 70S ribosomes, and replication machinery, allowing them partial autonomy in protein synthesis. This supports the endosymbiotic theory that these organelles originated from prokaryotic ancestors engulfed by eukaryotic cells, explaining their independence and role in energy metabolism.

8. (Matching Type)
Match the organelles with their functions:
A. Mitochondria – (i) Packaging of materials
B. Ribosomes – (ii) Protein synthesis
C. Golgi apparatus – (iii) Energy production
D. Lysosome – (iv) Intracellular digestion

1. A–iii, B–ii, C–i, D–iv
2. A–ii, B–iii, C–iv, D–i
3. A–i, B–iv, C–ii, D–iii
4. A–iv, B–i, C–iii, D–ii

Explanation (Answer: 1. A–iii, B–ii, C–i, D–iv):
Each organelle performs a specific role: mitochondria generate energy; ribosomes synthesize proteins; the Golgi apparatus modifies and packages materials; and lysosomes carry out intracellular digestion. Their coordination ensures smooth metabolic activity, protein secretion, and maintenance of cellular homeostasis essential for cell function.

9. (Fill in the Blanks)
______ are known as the protein factories of the cell.
1. Ribosomes
2. Golgi apparatus
3. Lysosomes
4. Mitochondria

Explanation (Answer: 1. Ribosomes):
Ribosomes are cellular structures composed of rRNA and proteins, responsible for translating mRNA into polypeptides. Found freely in cytoplasm or attached to the rough endoplasmic reticulum, ribosomes are universally present in all living cells, ensuring continuous protein synthesis necessary for cell growth and repair.

10. (Choose the Correct Statements)
Statement I: The Golgi apparatus helps in the formation of lysosomes.
Statement II: Ribosomes help in the synthesis of lipids.
1. Both statements are true.
2. Both statements are false.
3. Statement I is true but Statement II is false.
4. Statement I is false but Statement II is true.

Explanation (Answer: 3. Statement I is true but Statement II is false):
The Golgi apparatus forms primary lysosomes by packaging hydrolytic enzymes. Ribosomes, on the other hand, synthesize proteins, not lipids. Lipid synthesis occurs mainly in the smooth endoplasmic reticulum. Thus, the first statement is correct, while the second is incorrect, confirming the correct functional distinction between organelles.

Topic: Cell Organelles and Structures; Subtopic: Cilia, Endoplasmic Reticulum, Mitochondria, Kinetochore

Keyword Definitions:

• Cilia: Hair-like cellular projections involved in locomotion or movement of substances across the cell surface, made of microtubules arranged in a 9+2 pattern known as the axoneme.

• Endoplasmic Reticulum (ER): A network of membranous tubules that play a role in protein and lipid synthesis; ribosomes attach to rough ER.

• Mitochondria: The powerhouse of the cell where aerobic respiration occurs; inner membrane folds to form cristae.

• Kinetochore: A protein structure on the chromosome where spindle fibres attach during cell division for chromatid movement.

• Spindle fibres: Microtubule-based structures that segregate chromosomes during mitosis and meiosis.

• Ribosomes: Small cellular structures responsible for protein synthesis, found either freely in cytoplasm or attached to rough ER.

• Cristae: Infoldings of the inner mitochondrial membrane that increase surface area for ATP synthesis.

• Axoneme: The central structure of cilia and flagella composed of microtubules in a 9+2 arrangement.

Lead Question - 2024 (Jhajjhar)

Match List-I with List-II.
List-I          List-II
A. Cilia          I. Spindle fibres
B. Endoplasmic Reticulum          II. Cristae
C. Mitochondria          III. Axoneme
D. Kinetochore          IV. Ribosomes
Choose the correct answer from the options given below:

1. A-I, B-IV, C-II, D-III
2. A-III, B-IV, C-II, D-I
3. A-I, B-III, C-II, D-IV
4. A-III, B-II, C-I, D-IV

Explanation: Cilia are made up of an axoneme (III), Endoplasmic Reticulum has ribosomes (IV) attached on its surface, Mitochondria contain cristae (II) for ATP production, and Kinetochore binds to spindle fibres (I) during chromosome movement. Hence, the correct match is A-III, B-IV, C-II, D-I. These organelles collectively support movement, energy, and division functions.

1. Guessed Question: Which of the following structures is responsible for cell movement?
1. Ribosomes
2. Cilia
3. Lysosomes
4. Nucleolus
Explanation: Cilia are microtubule-based structures that produce movement either of the cell itself or of fluid along the cell surface. They function through coordinated beating driven by dynein arms. Thus, Cilia are responsible for locomotion and surface transport in many organisms.

2. Guessed Question: The Endoplasmic Reticulum with ribosomes attached is known as:
1. Rough ER
2. Smooth ER
3. Transitional ER
4. Golgi ER
Explanation: Rough Endoplasmic Reticulum (RER) has ribosomes attached to its cytoplasmic surface. These ribosomes synthesize proteins destined for secretion or membrane insertion. The RER gives a rough appearance under the microscope, differentiating it from Smooth ER.

3. Guessed Question: Which part of mitochondria contains enzymes for the electron transport chain?
1. Outer membrane
2. Cristae
3. Matrix
4. Intermembrane space
Explanation: The inner mitochondrial membrane forms folds called cristae, which contain the enzymes and complexes of the electron transport chain. These structures maximize surface area for oxidative phosphorylation and ATP synthesis. Thus, cristae are vital for cellular respiration efficiency.

4. Guessed Question: Kinetochore plays an important role in:
1. Cytokinesis
2. Spindle fibre attachment
3. Cell membrane formation
4. Lysosome synthesis
Explanation: The kinetochore is a protein complex located at the centromere of chromosomes. It serves as the attachment site for spindle fibres, ensuring accurate segregation of chromatids during cell division. Thus, kinetochore ensures proper chromosomal movement and stability during mitosis and meiosis.

5. Guessed Question: Axoneme is the structural core of:
1. Ribosome
2. Cilia and Flagella
3. Nucleolus
4. Centriole
Explanation: Axoneme is the central microtubule-based structure of cilia and flagella. It follows a 9+2 arrangement of microtubules that enable coordinated movement. Dynein arms attached to microtubules use ATP to generate bending motions for locomotion and fluid propulsion.

6. Guessed Question: Which organelle is known as the ‘Powerhouse of the Cell’?
1. Ribosome
2. Nucleus
3. Mitochondria
4. Lysosome
Explanation: Mitochondria generate ATP through oxidative phosphorylation during cellular respiration. The inner membrane’s cristae house enzymes for the electron transport chain and ATP synthase. Because it produces most of the cell’s energy, mitochondria are termed the ‘Powerhouse of the Cell’.

7. Assertion-Reason Question:
Assertion (A): Mitochondria contain their own DNA and ribosomes.
Reason (R): This allows mitochondria to synthesize some of their own proteins.
1. Both A and R are true, and R is the correct explanation of A
2. Both A and R are true, but R is not the correct explanation of A
3. A is true, but R is false
4. A is false, but R is true
Explanation: Mitochondria possess circular DNA and 70S ribosomes that enable synthesis of some mitochondrial proteins. Hence, both statements are true, and R correctly explains A, supporting their semi-autonomous nature in the cell.

8. Matching Type Question:
Match the following organelles with their main function:
A. Ribosomes – (i) Protein synthesis
B. Mitochondria – (ii) Energy production
C. Lysosomes – (iii) Intracellular digestion
D. Golgi apparatus – (iv) Packaging and secretion
Options:
1. A-i, B-ii, C-iii, D-iv
2. A-ii, B-i, C-iv, D-iii
3. A-iii, B-iv, C-ii, D-i
4. A-i, B-iii, C-ii, D-iv
Explanation: Ribosomes synthesize proteins (i), mitochondria produce ATP (ii), lysosomes digest waste (iii), and the Golgi apparatus packages materials for secretion (iv). Hence, the correct match is A-i, B-ii, C-iii, D-iv.

9. Fill in the Blanks:
The 9 + 2 arrangement of microtubules is characteristic of _______.
1. Centrioles
2. Cilia and Flagella
3. Basal body
4. Spindle fibres
Explanation: Cilia and flagella have a 9 + 2 microtubule structure forming the axoneme. Nine doublets surround two central microtubules, allowing flexibility and beating motion. This structure is essential for cell motility and surface transport.

10. Choose the Correct Statements (Statement I & Statement II):
Statement I: Ribosomes are non-membranous organelles involved in protein synthesis.
Statement II: Ribosomes are present only in eukaryotic cells.
1. Both statements are true
2. Both statements are false
3. Statement I is true, Statement II is false
4. Statement I is false, Statement II is true
Explanation: Ribosomes are non-membranous organelles that synthesize proteins, found in both prokaryotic (70S) and eukaryotic (80S) cells. Hence, Statement I is true and Statement II is false, highlighting their universal cellular importance.

Topic: Prokaryotic Cell Structure; Subtopic: Mesosomes and Cell Wall Formation

Keyword Definitions:

• Mesosomes: Infoldings of the bacterial plasma membrane that aid in cell wall formation, DNA replication, and respiration.

• Cell wall: A rigid outer layer made of peptidoglycan that maintains bacterial shape and protects against osmotic stress.

• Ribosomes: Small organelles responsible for protein synthesis in prokaryotic and eukaryotic cells.

• Golgi apparatus: Organelle involved in protein packaging and secretion in eukaryotic cells, absent in prokaryotes.

Lead Question - 2024 (Jhajjhar)
Cell wall formation in Bacteria is facilitated by:
1. Ribosomes
2. Mesosomes
3. Golgi Apparatus
4. Centrosomes

Explanation: Cell wall formation in bacteria is facilitated by Mesosomes. These are membrane infoldings that increase surface area for enzymatic activities and play a vital role in septum formation during cell division. Unlike Golgi bodies in eukaryotes, mesosomes function in distributing cell wall materials, DNA replication, and respiration, ensuring bacterial integrity and growth.

1. Which component is responsible for respiration in bacterial cells?
1. Ribosomes
2. Mesosomes
3. Nucleoid
4. Flagella

Explanation: In bacteria, mesosomes function as sites for cellular respiration, performing roles similar to mitochondria in eukaryotic cells. They contain respiratory enzymes that facilitate energy production through oxidative phosphorylation. Thus, mesosomes are essential for generating ATP required for bacterial metabolism and cellular processes.

2. Which structure is absent in prokaryotic cells?
1. Nucleoid
2. Ribosomes
3. Golgi apparatus
4. Plasma membrane

Explanation: Prokaryotic cells lack membrane-bound organelles such as the Golgi apparatus, mitochondria, and nucleus. They instead rely on structures like mesosomes for secretory and respiratory functions. The Golgi body’s absence differentiates prokaryotes from eukaryotes, emphasizing their simpler but efficient cellular organization for essential life processes.

3. What is the main component of the bacterial cell wall?
1. Cellulose
2. Chitin
3. Peptidoglycan
4. Pectin

Explanation: The bacterial cell wall is composed of peptidoglycan, a complex polymer of sugars and amino acids. It provides structural strength, protects against osmotic lysis, and maintains the cell’s shape. Gram-positive bacteria have thick peptidoglycan layers, while Gram-negative bacteria possess thinner layers with an outer lipid membrane.

4. In bacteria, genetic material is found in:
1. Nucleus
2. Nucleoid
3. Mesosome
4. Ribosome

Explanation: In bacteria, the genetic material is located in the nucleoid, a region containing circular DNA. It is not enclosed by a membrane. During cell division, mesosomes assist in distributing replicated DNA to daughter cells. This structure is unique to prokaryotes and is essential for inheritance and metabolic regulation.

5. Which structure performs a role similar to mitochondria in bacteria?
1. Mesosomes
2. Ribosomes
3. Nucleoid
4. Vacuoles

Explanation: Mesosomes in bacteria perform roles similar to mitochondria in eukaryotic cells. They provide a site for respiration and energy production through enzyme-mediated reactions. Their folded membrane structure maximizes surface area for metabolic activities essential for bacterial survival and efficient energy conversion within the cytoplasm.

6. Which of the following statements about mesosomes is incorrect?
1. They help in cell wall formation.
2. They are involved in respiration.
3. They are present in eukaryotic cells.
4. They assist in DNA replication.

Explanation: The statement “They are present in eukaryotic cells” is incorrect. Mesosomes are found exclusively in prokaryotic cells. They aid in cell wall formation, DNA replication, and respiration. Eukaryotes instead possess mitochondria and Golgi bodies for these functions, highlighting cellular structural differences between the two groups.

7. Assertion-Reason Type Question:
Assertion (A): Mesosomes are involved in bacterial cell wall formation.
Reason (R): They are invaginations of the plasma membrane that secrete enzymes necessary for peptidoglycan synthesis.
1. Both A and R are true, and R is the correct explanation of A.
2. Both A and R are true, but R is not the correct explanation of A.
3. A is true, but R is false.
4. A is false, but R is true.

Explanation: Both statements are true, and the Reason correctly explains the Assertion. Mesosomes form vesicular structures that help secrete wall-forming enzymes. They ensure proper septum formation and cell division, performing crucial roles in the synthesis of peptidoglycan, essential for bacterial growth and stability.

8. Matching Type Question:
Match List-I with List-II
List-I List-II
A. Ribosomes I. Protein synthesis
B. Mesosomes II. Respiration
C. Nucleoid III. Genetic material
D. Flagella IV. Motility

Options:
1. A-I, B-II, C-III, D-IV
2. A-II, B-I, C-IV, D-III
3. A-III, B-IV, C-II, D-I
4. A-IV, B-II, C-I, D-III

Explanation: The correct match is A-I, B-II, C-III, D-IV. Ribosomes perform protein synthesis, mesosomes assist in respiration, nucleoid contains genetic material, and flagella provide motility. Each bacterial component plays a distinct functional role essential for maintaining cellular integrity and performing vital physiological processes.

9. Fill in the Blanks Type Question:
The bacterial cell wall is mainly composed of ________.
1. Peptidoglycan
2. Cellulose
3. Glycogen
4. Lignin

Explanation: The bacterial cell wall primarily consists of peptidoglycan, a strong and flexible polymer providing rigidity and protection. It forms a mesh-like structure surrounding the plasma membrane. Peptidoglycan synthesis involves enzymes produced by mesosomes, ensuring cell stability during growth and division, maintaining bacterial shape and resistance to lysis.

10. Choose the Correct Statements (Statement I & II):
Statement I: Mesosomes are artifacts of cell preparation.
Statement II: They play an important role in respiration and cell wall formation.
1. Both statements are true.
2. Both statements are false.
3. Statement I is true, Statement II is false.
4. Statement I is false, Statement II is true.

Explanation: Statement I is false and Statement II is true. Mesosomes are functional membrane invaginations in bacteria aiding in respiration and wall synthesis. Although some artificial structures appear during microscopy, genuine mesosomes serve real physiological functions essential for bacterial metabolism and division.

Topic: Cell Organelles; Subtopic: Mitochondria and Chloroplast – Structure and Functions

Keyword Definitions:
• Mitochondria: Double membrane-bound organelles responsible for ATP production through aerobic respiration.
• Chloroplast: Double membrane-bound organelles found in plant cells, responsible for photosynthesis.
• Double membrane: Two-layered structure that separates the organelle from cytoplasm, maintaining specific conditions inside.
• Permeability: Ability of membrane to allow selective passage of molecules.
• ATP: Adenosine triphosphate, the energy currency of cells produced in mitochondria.

Lead Question - 2024
Given below are two statements :
Statement I: Mitochondria and chloroplasts are both double membrane bound organelles.
Statement II: Inner membrane of mitochondria is relatively less permeable, as compared to chloroplast.
In the light of the above statements, choose the most appropriate answer from the options given below:
(1) Both statement I and statement II are incorrect
(2) Statement I is correct but statement II is incorrect
(3) Statement I is incorrect but statement II is correct
(4) Both statement I and statement II are correct

Explanation:
Both mitochondria and chloroplasts are double membrane-bound organelles with specialized internal structures. The inner mitochondrial membrane is highly impermeable due to transport proteins and cristae formation, ensuring efficient ATP synthesis. The chloroplast inner membrane is more permeable to small molecules and ions. Therefore, both statements I and II are correct. Hence, option (4) is correct.

1. The main function of mitochondria is:
(1) Photosynthesis
(2) Protein synthesis
(3) ATP production
(4) Lipid synthesis

Explanation:
Mitochondria are known as the “powerhouses of the cell” because they generate ATP through oxidative phosphorylation during aerobic respiration. Their folded inner membrane, called cristae, provides surface area for electron transport and ATP synthase activity. This continuous ATP supply supports all energy-dependent cellular functions. Hence, option (3) is correct.

2. Which pigment is responsible for trapping solar energy in chloroplasts?
(1) Chlorophyll
(2) Carotene
(3) Xanthophyll
(4) Anthocyanin

Explanation:
Chlorophyll is the principal pigment located in the thylakoid membranes of chloroplasts. It captures solar energy and converts it into chemical energy during photosynthesis. Chlorophyll a and b absorb light mainly in blue and red regions, initiating photochemical reactions. Thus, option (1) is correct.

3. The inner membrane of mitochondria is folded into:
(1) Cisternae
(2) Cristae
(3) Thylakoids
(4) Lamellae

Explanation:
The inner membrane of mitochondria forms numerous inward folds called cristae. These increase surface area for enzymes involved in the electron transport chain and ATP synthesis. Cristae play a vital role in maximizing energy production efficiency within each mitochondrion. Therefore, option (2) is correct.

4. Which of the following cell organelles contain their own DNA and ribosomes?
(1) Lysosome and Golgi apparatus
(2) Endoplasmic reticulum and ribosome
(3) Mitochondria and chloroplast
(4) Peroxisome and vacuole

Explanation:
Both mitochondria and chloroplasts possess their own DNA and 70S ribosomes, enabling semi-autonomous function. They can synthesize some of their proteins and enzymes independently. This supports the endosymbiotic theory of organelle evolution. Hence, option (3) is correct.

5. The site of the light reaction of photosynthesis is:
(1) Stroma
(2) Matrix
(3) Thylakoid membrane
(4) Intermembrane space

Explanation:
Light reactions of photosynthesis occur in the thylakoid membranes of chloroplasts, where chlorophyll absorbs sunlight. This leads to ATP and NADPH generation, required for the dark reactions in the stroma. Water splitting and oxygen evolution also occur here. Hence, option (3) is correct.

6. Which one of the following is not a function of mitochondria?
(1) Krebs cycle
(2) Electron transport
(3) Glycolysis
(4) ATP synthesis

Explanation:
Glycolysis occurs in the cytoplasm, not in mitochondria. Mitochondria conduct the Krebs cycle and oxidative phosphorylation in their matrix and inner membrane, respectively. Thus, option (3) is correct.

Assertion-Reason Question
7. Assertion (A): Mitochondria are called powerhouses of the cell.
Reason (R): They are the main site for ATP production through oxidative phosphorylation.
(1) Both A and R are true, and R is the correct explanation of A.
(2) Both A and R are true, but R is not the correct explanation of A.
(3) A is true, but R is false.
(4) A is false, but R is true.

Explanation:
Both statements are true. Mitochondria synthesize ATP by oxidative phosphorylation using the electron transport chain and ATP synthase. This energy powers essential cellular functions, justifying the term “powerhouse.” Hence, option (1) is correct.

Matching Type Question
8. Match the following:
A. Cristae – (i) Photosynthesis
B. Stroma – (ii) Site of Krebs cycle
C. Matrix – (iii) Folds of inner mitochondrial membrane
D. Thylakoid – (iv) Site of light reaction

(1) A-iii, B-i, C-ii, D-iv
(2) A-ii, B-iii, C-iv, D-i
(3) A-i, B-ii, C-iii, D-iv
(4) A-iv, B-ii, C-i, D-iii

Explanation:
Cristae are folds of the inner mitochondrial membrane; stroma is the site of dark reactions; matrix hosts the Krebs cycle; and thylakoids perform light reactions. Together, these ensure energy flow in cells. Thus, option (1) is correct.

Fill in the Blanks Question
9. The double membrane of mitochondria separates ______ and ______ compartments.
(1) Matrix, Stroma
(2) Outer membrane, Intermembrane space
(3) Intermembrane space, Matrix
(4) Thylakoid, Lumen

Explanation:
The double membrane of mitochondria creates two compartments: the intermembrane space between the inner and outer membranes, and the matrix enclosed within. These compartments enable compartmentalization of biochemical reactions. Hence, option (3) is correct.

Choose the Correct Statements Question
10. Statement I: Both mitochondria and chloroplasts possess circular DNA.
Statement II: Both are semi-autonomous organelles capable of self-replication.
(1) Both statements I and II are true.
(2) Both statements I and II are false.
(3) Statement I is true, Statement II is false.
(4) Statement I is false, Statement II is true.

Explanation:
Both statements are true. Mitochondria and chloroplasts have their own circular DNA and 70S ribosomes, supporting the endosymbiotic theory. They can synthesize some proteins and replicate independently within cells. Hence, option (1) is correct.

Topic: Cell Organelles and Structures; Subtopic: Ultrastructure of Cell Organelles and Associated Components

Keyword Definitions:

• Axoneme: The core structure of cilia and flagella composed of microtubules arranged in a 9+2 pattern that enables motility.

• Cartwheel Pattern: A microtubule arrangement seen in centrioles, characterized by nine triplets surrounding a central hub.

• Crista: The inner membrane folds of mitochondria that increase the surface area for enzymatic reactions of respiration.

• Satellite: A small chromosomal segment separated by a secondary constriction and often associated with nucleolar organizer regions.

• Centriole: A cylindrical cell structure made of microtubule triplets, playing a role in spindle formation during cell division.

Lead Question - 2024
Match List I with List II
A. Axoneme  I. Centriole
B. Cartwheel pattern  II. Cilia and flagella
C. Crista  III. Chromosome
D. Satellite  IV. Mitochondria

Choose the correct answer from the options given below:
(1) A-IV, B-II, C-III, D-I
(2) A-II, B-IV, C-I, D-III
(3) A-II, B-I, C-IV, D-III
(4) A-I, B-II, C-III, D-IV

Explanation: The correct answer is (3) A-II, B-I, C-IV, D-III. The axoneme forms the core of cilia and flagella; the cartwheel pattern occurs in centrioles; cristae are inner folds of mitochondria that enhance ATP production; and satellites are small chromosomal parts linked to nucleolus formation. These cellular structures perform specialized and vital cellular roles.

1. Which of the following cell structures shows a 9 + 2 arrangement of microtubules?
(1) Basal body
(2) Flagella
(3) Centriole
(4) Spindle fiber
Explanation: The correct answer is (2) Flagella. Flagella and cilia possess an axoneme with a 9 + 2 microtubule pattern—nine peripheral doublets surrounding two central singlets. This arrangement enables motility by coordinated sliding of microtubules using dynein arms, powered by ATP from mitochondria near the base of flagella.

2. The cartwheel structure is characteristic of which organelle?
(1) Nucleolus
(2) Centriole
(3) Ribosome
(4) Endoplasmic reticulum
Explanation: The correct answer is (2) Centriole. The centriole displays a cartwheel pattern, where nine triplet microtubules radiate from a central hub. It organizes the spindle apparatus during cell division and forms basal bodies of cilia and flagella. Its structure ensures proper chromosomal segregation in eukaryotic cells.

3. Cristae are functionally important because they:
(1) Increase the surface area for ATP synthesis
(2) Help in protein synthesis
(3) Form structural filaments
(4) Contain ribosomes for glycolysis
Explanation: The correct answer is (1) Increase the surface area for ATP synthesis. Cristae are folds of the inner mitochondrial membrane that house enzymes of the electron transport chain and ATP synthase complexes. Their extensive surface area facilitates efficient oxidative phosphorylation, leading to maximum energy yield during cellular respiration.

4. A satellite on a chromosome is associated with which structure?
(1) Centromere
(2) Secondary constriction
(3) Telomere
(4) Primary constriction
Explanation: The correct answer is (2) Secondary constriction. Satellites are small chromosomal segments separated by secondary constrictions, often forming the nucleolar organizer region (NOR). These regions are responsible for ribosomal RNA synthesis, linking chromosomal structure to nucleolar function during cell activity and division.

5. The core structure of cilia and flagella is called:
(1) Basal granule
(2) Axoneme
(3) Microfilament
(4) Tonoplast
Explanation: The correct answer is (2) Axoneme. The axoneme is the structural core of cilia and flagella, composed of microtubules in a 9 + 2 arrangement. It provides rigidity and coordinated movement, driven by dynein arms and powered by ATP, ensuring locomotion or movement of fluid across cell surfaces.

6. The basal body of cilia originates from which structure?
(1) Nucleus
(2) Centriole
(3) Ribosome
(4) Lysosome
Explanation: The correct answer is (2) Centriole. Centrioles act as basal bodies from which cilia and flagella develop. The structural similarity between centrioles and basal bodies, both possessing a 9 × 3 microtubule arrangement, allows efficient anchoring and initiation of axoneme formation for motile cellular appendages.

7. Assertion-Reason Type Question:
Assertion (A): Mitochondrial cristae contain enzymes for oxidative phosphorylation.
Reason (R): Cristae increase surface area for aerobic respiration.
(1) Both A and R are true, and R is the correct explanation of A.
(2) Both A and R are true, but R is not the correct explanation of A.
(3) A is true, but R is false.
(4) A is false, but R is true.
Explanation: The correct answer is (1). Cristae are inner folds of the mitochondrial membrane containing enzyme complexes for oxidative phosphorylation and ATP synthesis. Their large surface area enhances metabolic reactions, maximizing energy production efficiency in actively respiring cells such as muscle or nerve cells.

8. Matching Type Question:
Match the following organelles with their functions:
A. Nucleolus  I. Ribosome formation
B. Mitochondria  II. ATP production
C. Centriole  III. Spindle organization
D. Lysosome  IV. Intracellular digestion
(1) A-I, B-II, C-III, D-IV
(2) A-II, B-I, C-IV, D-III
(3) A-IV, B-I, C-III, D-II
(4) A-III, B-II, C-I, D-IV
Explanation: The correct answer is (1). The nucleolus synthesizes ribosomal subunits, mitochondria produce ATP through respiration, centrioles organize spindle fibers for chromosomal movement, and lysosomes contain hydrolytic enzymes for digestion. These organelles collectively ensure cellular energy management, reproduction, and maintenance.

9. Fill in the Blanks:
The structural core of eukaryotic flagella is called the ________.
(1) Crista
(2) Axoneme
(3) Centriole
(4) Basal body
Explanation: The correct answer is (2) Axoneme. The axoneme forms the functional core of cilia and flagella with a 9 + 2 microtubule arrangement. It provides flexibility and motility through dynein-driven bending, enabling cells like sperm and protozoa to move efficiently in fluid environments.

10. Choose the Correct Statements:
Statement I: Centrioles lack a membrane but are involved in cell division.
Statement II: Cristae are parts of the outer mitochondrial membrane.
(1) Both statements are true.
(2) Both statements are false.
(3) Statement I is true, Statement II is false.
(4) Statement I is false, Statement II is true.
Explanation: The correct answer is (3). Centrioles are non-membranous structures that play a critical role in spindle formation during cell division. Cristae, however, are folds of the inner, not outer, mitochondrial membrane, containing enzymes for energy production during oxidative phosphorylation in mitochondria.

Topic: Cell Organelles; Subtopic: Chloroplast DNA (cpDNA)

Keyword Definitions:

• Chloroplast: A double-membrane organelle in plant cells responsible for photosynthesis, converting light energy into chemical energy.

• DNA: Deoxyribonucleic acid, the hereditary material carrying genetic information for structure and function.

• cpDNA: The DNA found within chloroplasts, inherited maternally in most plants, and responsible for protein synthesis related to photosynthesis.

• Endosymbiotic theory: Explains the origin of chloroplasts and mitochondria from ancient prokaryotic cells through symbiosis.

• Ribosomes (70S): Prokaryote-like ribosomes present in chloroplasts for in situ protein synthesis.

Lead Question – 2024

The DNA present in chloroplast is:
(1) Circular, double stranded
(2) Linear, single stranded
(3) Circular, single stranded
(4) Linear, double stranded

Explanation: Chloroplast DNA (cpDNA) is circular and double-stranded, resembling prokaryotic DNA, supporting the endosymbiotic theory. It encodes for rRNA, tRNA, and several proteins essential for photosynthesis. cpDNA replicates independently of nuclear DNA and is maternally inherited in most plant species. Hence, the correct answer is option (1) Circular, double stranded.

1. The DNA present in mitochondria is:
(1) Linear and single-stranded
(2) Circular and double-stranded
(3) Circular and single-stranded
(4) Linear and double-stranded

Mitochondrial DNA (mtDNA) is circular, double-stranded, and similar to bacterial DNA. It encodes essential enzymes for oxidative phosphorylation and is maternally inherited. This independent DNA replication system indicates the endosymbiotic origin of mitochondria. Therefore, the correct answer is option (2) Circular and double-stranded.

2. Which of the following organelles possesses 70S ribosomes?
(1) Endoplasmic reticulum
(2) Nucleus
(3) Mitochondria
(4) Golgi apparatus

Mitochondria contain 70S ribosomes, similar to those in prokaryotes. This feature enables them to synthesize some of their own proteins, supporting the endosymbiotic theory. In contrast, cytoplasmic ribosomes are 80S. Hence, the correct answer is option (3) Mitochondria.

3. Which statement correctly explains the endosymbiotic origin of chloroplasts?
(1) They evolved from cyanobacteria
(2) They originated from mitochondria
(3) They formed from lysosomes
(4) They evolved from Golgi bodies

Chloroplasts are believed to have evolved from cyanobacteria through endosymbiosis, where ancient eukaryotic cells engulfed photosynthetic bacteria that became permanent organelles. This is supported by the presence of circular DNA, 70S ribosomes, and autonomous division. Hence, the correct answer is option (1) They evolved from cyanobacteria.

4. Which component is absent in chloroplast DNA?
(1) Histone proteins
(2) Genes for rRNA
(3) Genes for tRNA
(4) Non-coding regions

Chloroplast DNA lacks histone proteins, unlike nuclear DNA, and remains in a naked circular form. It contains genes for rRNA, tRNA, and photosynthetic proteins. The absence of histones is a prokaryotic feature, supporting its bacterial ancestry. Hence, the correct answer is option (1) Histone proteins.

5. The genetic system of chloroplast is similar to that of:
(1) Viruses
(2) Bacteria
(3) Fungi
(4) Protozoa

Chloroplast genetic system closely resembles bacteria due to circular DNA, 70S ribosomes, and independent replication. This prokaryote-like organization supports the endosymbiotic origin hypothesis. Hence, the correct answer is option (2) Bacteria.

6. In plants, chloroplast inheritance is usually:
(1) Maternal
(2) Paternal
(3) Biparental
(4) Random

Chloroplast DNA (cpDNA) is typically inherited maternally through the ovum. This uniparental inheritance ensures uniformity of chloroplast traits across generations. Paternal inheritance is rare in plants. Therefore, the correct answer is option (1) Maternal.

Assertion–Reason Type Question

7. Assertion (A): Chloroplasts can synthesize some of their own proteins.
Reason (R): Chloroplasts contain circular DNA and 70S ribosomes.

(1) Both A and R are true and R is the correct explanation of A
(2) Both A and R are true but R is not the correct explanation of A
(3) A is true but R is false
(4) A is false but R is true

Chloroplasts possess circular DNA and 70S ribosomes, enabling them to synthesize certain proteins autonomously. Hence, both Assertion and Reason are true, and R correctly explains A. The correct option is (1).

8. Matching Type Question

Match the organelle with its genetic material:
A. Nucleus – I. Linear, double-stranded DNA
B. Mitochondria – II. Circular, double-stranded DNA
C. Chloroplast – III. Circular, double-stranded DNA
D. Virus – IV. Linear or circular, single or double-stranded nucleic acid

(1) A–I, B–II, C–III, D–IV
(2) A–II, B–III, C–IV, D–I
(3) A–III, B–IV, C–I, D–II
(4) A–IV, B–II, C–III, D–I

Nucleus contains linear double-stranded DNA, mitochondria and chloroplasts contain circular double-stranded DNA, while viruses have varied nucleic acids. Therefore, option (1) A–I, B–II, C–III, D–IV is correct.

9. Fill in the Blanks Question

Chloroplast ribosomes are of ______ type.

(1) 70S
(2) 80S
(3) 90S
(4) 60S

Chloroplast ribosomes are of 70S type, similar to prokaryotes, allowing them to synthesize certain proteins required for photosynthesis. Cytoplasmic ribosomes are 80S, distinguishing them from chloroplast and mitochondrial ribosomes. Hence, the correct answer is option (1) 70S.

10. Choose the Correct Statements (Statement I & II)

Statement I: Chloroplast DNA is linear in nature.
Statement II: Chloroplast DNA shows semiconservative replication.

(1) Both statements are true
(2) Statement I true, Statement II false
(3) Statement I false, Statement II true
(4) Both statements are false

Chloroplast DNA is circular, not linear, and replicates semiconservatively like nuclear DNA. Each daughter molecule receives one parental and one new strand. Hence, Statement I is false and Statement II is true. The correct option is (3).

Topic: Cell Organelles; Subtopic: Structure and Function of Organelles

Keyword Definitions:

• Nucleolus: A dense region inside the nucleus where ribosomal RNA (rRNA) is synthesized.

• Centriole: A cylindrical cell structure involved in spindle formation during cell division.

• Leucoplasts: Colorless plastids in plant cells that store starch, oils, or proteins.

• Golgi Apparatus: Organelle responsible for packaging and secretion of materials, and formation of glycolipids and glycoproteins.

• rRNA: Ribosomal RNA essential for ribosome assembly.

• Glycolipids: Lipids with carbohydrate attached, formed in Golgi bodies.

• Cartwheel Structure: Typical arrangement of microtubules in centrioles (9+0 pattern).

• Cell Organelle: Specialized structures within a cell performing distinct functions.

Lead Question – 2024

Match List I with List II

List I          List II
(1) Nucleolus      I. Site of formation of glycolipid
(2) Centriole        II. Organization like the cartwheel
(3) Leucoplasts     III. Site for active ribosomal RNA synthesis
(4) Golgi apparatus IV. For storing nutrients

Choose the correct answer from the options given below:
(1) A–II, B–III, C–I, D–IV
(2) A–III, B–IV, C–II, D–I
(3) A–I, B–II, C–III, D–IV
(4) A–III, B–II, C–IV, D–I

Explanation: The nucleolus is the site for active ribosomal RNA synthesis, centrioles exhibit a cartwheel-like organization with microtubules arranged in a 9+0 pattern, leucoplasts store nutrients like starch and oil, and the Golgi apparatus is responsible for glycolipid formation. Thus, the correct match is A–III, B–II, C–IV, D–I. These structures collectively maintain cell organization and biochemical efficiency. (Answer: 4)

1. Single Correct Answer:
Which of the following organelles is known as the “factory” for ribosomal RNA synthesis?
(1) Endoplasmic Reticulum
(2) Nucleolus
(3) Golgi Apparatus
(4) Mitochondria

Explanation: The nucleolus is the dense, spherical structure within the nucleus responsible for rRNA synthesis and ribosome assembly. It plays a central role in protein synthesis. The ER is involved in protein and lipid transport, Golgi modifies proteins, and mitochondria generate ATP. Hence, nucleolus is the correct choice. (Answer: 2)

2. Single Correct Answer:
Which structure helps in spindle fiber formation during cell division?
(1) Lysosome
(2) Centriole
(3) Golgi Body
(4) Ribosome

Explanation: Centrioles are cylindrical cell structures located near the nucleus and help in organizing spindle fibers during mitosis and meiosis. They possess a 9+0 microtubule arrangement resembling a cartwheel. Lysosomes aid in digestion, Golgi in packaging, and ribosomes in protein synthesis. (Answer: 2)

3. Single Correct Answer:
Leucoplasts are primarily involved in:
(1) Photosynthesis
(2) Storage of food materials
(3) Lipid oxidation
(4) Protein synthesis

Explanation: Leucoplasts are colorless plastids found in plant cells that function mainly in storage of nutrients such as starch (amyloplasts), oils (elaioplasts), or proteins (aleuroplasts). They are abundant in non-photosynthetic tissues like roots and seeds. (Answer: 2)

4. Single Correct Answer:
Which cell organelle is responsible for the formation of glycolipids and glycoproteins?
(1) Ribosome
(2) Mitochondria
(3) Golgi Apparatus
(4) Peroxisome

Explanation: The Golgi apparatus modifies, packages, and secretes materials, and it is involved in the synthesis of glycolipids and glycoproteins. Ribosomes synthesize proteins, mitochondria generate ATP, and peroxisomes detoxify substances. Thus, Golgi apparatus plays a crucial role in post-translational modification. (Answer: 3)

5. Single Correct Answer:
Which structure in the cell exhibits a cartwheel-like pattern?
(1) Centriole
(2) Cilium
(3) Lysosome
(4) Vacuole

Explanation: The centriole shows a characteristic cartwheel arrangement of nine triplets of microtubules, forming the 9+0 pattern. This structure helps in spindle organization and cilia formation. Other organelles like lysosomes or vacuoles lack this unique architecture. (Answer: 1)

6. Single Correct Answer:
Which organelle is called the “cell’s post office”?
(1) Endoplasmic Reticulum
(2) Golgi Apparatus
(3) Ribosome
(4) Lysosome

Explanation: The Golgi apparatus is termed the “cell’s post office” as it packages, modifies, and transports materials synthesized in the ER to their destinations. It forms vesicles that deliver proteins and lipids. This function is essential for secretion and membrane formation. (Answer: 2)

7. Assertion-Reason:
Assertion (A): Golgi apparatus helps in secretion of cellular products.
Reason (R): Golgi apparatus packages proteins and lipids in vesicles.
(1) Both A and R are true, R explains A
(2) Both A and R are true, R does not explain A
(3) A true, R false
(4) A false, R true

Explanation: Golgi apparatus modifies and packages materials into vesicles for secretion or transport to various cell parts. Hence, both the assertion and reason are true, and the reason correctly explains the assertion. This function is vital in exocytosis and membrane repair. (Answer: 1)

8. Matching Type:
Match the following:
A. Nucleolus – (i) Ribosome synthesis
B. Centriole – (ii) Spindle fiber organization
C. Leucoplast – (iii) Nutrient storage
D. Golgi body – (iv) Glycolipid formation
Options:
(1) A-i, B-ii, C-iii, D-iv
(2) A-ii, B-iii, C-iv, D-i
(3) A-iv, B-i, C-ii, D-iii
(4) A-iii, B-ii, C-i, D-iv

Explanation: The nucleolus synthesizes ribosomal RNA, centrioles form spindle fibers, leucoplasts store nutrients, and Golgi bodies form glycolipids. Each organelle performs a distinct and vital cellular function ensuring coordination in cellular metabolism and growth. (Answer: 1)

9. Fill in the Blanks:
The cartwheel-like structure is characteristic of the ___, which assists in ___ formation.
(1) Centriole, spindle fiber
(2) Golgi body, vesicle
(3) Nucleolus, ribosome
(4) Leucoplast, starch

Explanation: The centriole exhibits a cartwheel pattern of microtubules and assists in spindle fiber formation during cell division, ensuring proper chromosome segregation. Golgi, nucleolus, and leucoplast perform unrelated functions. (Answer: 1)

10. Choose Correct Statements:
Statement I: The Golgi apparatus is responsible for packaging and secretion.
Statement II: The nucleolus stores nutrients.
(1) Both statements are true
(2) Statement I true, Statement II false
(3) Statement I false, Statement II true
(4) Both statements are false

Explanation: The Golgi apparatus packages and secretes cellular materials, including proteins and lipids, while the nucleolus synthesizes rRNA, not nutrients. Hence, Statement I is true, and Statement II is false. Understanding their distinct roles is essential for cell biology. (Answer: 2)

Topic: Prokaryotic Cell Structure; Subtopic: Mesosomes in Bacteria

Keyword Definitions:

• Bacteria: Unicellular prokaryotic microorganisms without a membrane-bound nucleus.

• Mesosome: Infoldings of the plasma membrane in bacteria, involved in cellular processes like DNA replication and cell division.

• Plasma membrane: The phospholipid bilayer that surrounds the cytoplasm of cells, regulating entry and exit of substances.

• DNA replication: The process of producing two identical copies of DNA from one original DNA molecule.

• Cell wall: A rigid layer outside the plasma membrane providing structural support and shape to bacterial cells.

• Prokaryotic cell: A cell lacking membrane-bound organelles, with genetic material in the nucleoid region.

• Nucleoid: Region in a prokaryotic cell where the DNA is localized.

• Infolding: The inward folding of a membrane to increase surface area or facilitate specific cellular functions.

• Cell division: The process by which a parent cell divides into two daughter cells.

• Replication: The biological process of copying genetic material.

• Organelle: Specialized structure within a cell performing distinct functions.

Lead Question - 2023 (Manipur)

Given below are two statements:

I: In bacteria, the mesosomes are formed by the extensions of the plasma membrane.

II: The mesosomes, in bacteria, help in DNA replication and cell wall formation.

In light of the above statements, choose the most appropriate answer from the options given below:

1. Statement I is correct but Statement II is incorrect

2. Statement I is incorrect but Statement II is correct

3. Both Statement I and Statement II are correct

4. Both Statement I and Statement II are incorrect

Explanation:

Mesosomes are folded extensions of the bacterial plasma membrane, increasing surface area for enzymatic activities. They play roles in DNA replication, segregation, and cell wall formation during division. Both statements I and II correctly describe their structure and functions. While their existence is debated in modern microscopy due to artifacts, traditionally, they are considered functional in bacterial cells. Correct answer is 3.

1. Single Correct Answer MCQ:

Mesosomes in bacteria are primarily composed of:

1. Proteins

2. Phospholipid bilayer

3. Peptidoglycan

4. Ribosomal RNA

Explanation:

Mesosomes are infoldings of the bacterial plasma membrane, which is a phospholipid bilayer with embedded proteins. They are not composed of peptidoglycan, proteins alone, or ribosomal RNA. Correct answer is 2.

2. Single Correct Answer MCQ:

The primary function of mesosomes is:

1. Energy production

2. DNA replication and cell wall synthesis

3. Protein synthesis

4. Photosynthesis

Explanation:

Mesosomes facilitate DNA replication, segregation, and cell wall formation in bacteria. They do not directly participate in protein synthesis, photosynthesis, or energy production. Correct answer is 2.

3. Single Correct Answer MCQ:

Mesosomes are considered artifacts because:

1. They are permanent structures

2. They result from chemical fixation during microscopy

3. They are part of the ribosome

4. They are extracellular structures

Explanation:

Modern microscopy suggests mesosomes may appear due to chemical fixation during electron microscopy, making them artifacts rather than permanent structures. They are intracellular, not ribosomes or extracellular. Correct answer is 2.

4. Single Correct Answer MCQ:

Which process is directly assisted by mesosomes?

1. Glycolysis

2. DNA replication

3. Protein folding

4. Photosynthesis

Explanation:

Mesosomes provide surface area for enzymes involved in DNA replication and segregation. They are not directly involved in glycolysis, protein folding, or photosynthesis. Correct answer is 2.

5. Single Correct Answer MCQ:

Mesosomes are located in:

1. Eukaryotic nucleus

2. Bacterial plasma membrane

3. Mitochondria

4. Cytoskeleton

Explanation:

Mesosomes are extensions of the bacterial plasma membrane in prokaryotes. They are absent in eukaryotic nuclei, mitochondria, or the cytoskeleton. Correct answer is 2.

6. Single Correct Answer MCQ:

Formation of mesosomes increases:

1. Cytoplasmic volume

2. Membrane surface area

3. Ribosomal density

4. Cell motility

Explanation:

Mesosomes are infoldings of the plasma membrane, increasing surface area for enzymatic reactions and DNA replication. They do not increase cytoplasmic volume, ribosome density, or motility. Correct answer is 2.

7. Assertion-Reason MCQ:

Assertion (A): Mesosomes assist in bacterial cell division.

Reason (R): Mesosomes provide sites for DNA replication and septum formation.

1. Both A and R are true and R explains A

2. Both A and R are true but R does not explain A

3. A is true but R is false

4. Both A and R are false

Explanation:

Mesosomes facilitate DNA replication and septum formation during bacterial cell division. Both the assertion and reason are correct, and the reason explains the function described. Correct answer is 1.

8. Matching Type MCQ:

Match the structure with its role:

A. Mesosome — (i) DNA replication

B. Ribosome — (ii) Protein synthesis

C. Peptidoglycan layer — (iii) Cell wall strength

D. Flagellum — (iv) Motility

1. A-(i), B-(ii), C-(iii), D-(iv)

2. A-(ii), B-(i), C-(iv), D-(iii)

3. A-(iii), B-(iv), C-(ii), D-(i)

4. A-(iv), B-(iii), C-(i), D-(ii)

Explanation:

Mesosomes assist DNA replication, ribosomes synthesize proteins, peptidoglycan provides cell wall strength, and flagella enable bacterial motility. Correct matching is A-(i), B-(ii), C-(iii), D-(iv), which is option 1.

9. Fill in the Blanks MCQ:

Mesosomes are formed by ______ of the plasma membrane.

1. Infoldings

2. Outgrowth

3. Fragmentation

4. Dissolution

Explanation:

Mesosomes are formed by infoldings of the bacterial plasma membrane, increasing surface area for enzymatic activity and DNA replication. Correct answer is 1.

10. Choose the correct statements MCQ:

Statement I: Mesosomes aid in bacterial DNA replication.

Statement II: Mesosomes are present in eukaryotic cells.

1. Statement I only

2. Statement II only

3. Both statements are true

4. Both statements are false

Explanation:

Mesosomes assist in DNA replication in bacteria (prokaryotes) but are not present in eukaryotic cells. Therefore, only Statement I is correct. Correct answer is 1.

Topic: Cell Organelles; Subtopic: Golgi Apparatus

Keyword Definitions:

• Golgi Apparatus: Membrane-bound organelle involved in protein and lipid modification, sorting, and packaging for secretion or cellular use.

• Glycoproteins: Proteins with covalently attached carbohydrate groups, important for cell recognition and signaling.

• Glycolipids: Lipids with carbohydrate chains, involved in membrane stability and cell signaling.

• Endoplasmic Reticulum (ER): Organelle that synthesizes proteins (rough ER) and lipids (smooth ER).

• ATP: Adenosine triphosphate, the primary energy currency of the cell.

• Protein Modification: Chemical alterations to proteins such as glycosylation or phosphorylation.

• Transport of Ions: Movement of ions across membranes, often facilitated by channels or pumps.

• Mechanical Support: Structural stability provided to cells, often by cytoskeleton rather than Golgi.

• Secretion: Process of exporting molecules from the cell via vesicles.

• Vesicles: Small membrane-bound compartments used for transport within the cell.

• Cellular Organelle: Specialized subunit within a cell with specific functions.

Lead Question - 2023 (Manipur):

Which of the following statements are correct in the context of Golgi apparatus?

A: It is the important site for the formation of glycoprotein and glycolipids
B: It produces cellular energy in the form of ATP
C: It modifies the protein synthesized by ribosomes on ER
D: It facilitates the transport of ions
E: It provides mechanical support

Choose the most appropriate answer from the options given below:

1. (B) and (C) only
2. (A) and (C) only
3. (A) and (D) only

Explanation: Correct answer is option 2: (A) and (C) only. Golgi apparatus is a central organelle in post-translational modification of proteins, including glycosylation to form glycoproteins and glycolipids. Proteins synthesized on rough ER are modified and packaged into vesicles by Golgi for secretion or cellular use. It does not produce ATP, transport ions, or provide mechanical support, which are functions of mitochondria, ion channels, and cytoskeleton respectively. Understanding Golgi structure and function is fundamental for cellular biology, secretory pathways, and molecular trafficking, highlighting its role in processing and sorting biomolecules within eukaryotic cells.

Guessed MCQs:

1. Single Correct Answer MCQ: The Golgi apparatus primarily functions in:
(A) Energy production
(B) Protein modification and sorting
(C) DNA replication
(D) Ion transport
Explanation: Correct answer is (B). Golgi apparatus modifies proteins synthesized by ER, including glycosylation, phosphorylation, and packaging into vesicles for secretion or cellular targeting. It is central to post-translational processing and trafficking. It does not generate energy, replicate DNA, or move ions, which are functions of mitochondria, nucleus, and ion channels. Its role ensures proper protein maturation, secretion, and functional localization within cells.

2. Single Correct Answer MCQ: Glycosylation occurs in:
(A) Mitochondria
(B) Golgi apparatus
(C) Ribosomes
(D) Nucleus
Explanation: Correct answer is (B). Glycosylation is the attachment of carbohydrate groups to proteins or lipids, forming glycoproteins and glycolipids. This modification occurs in the Golgi apparatus after initial protein synthesis on rough ER. It is essential for protein stability, cell signaling, and membrane targeting. Mitochondria, ribosomes, and nucleus do not perform glycosylation. Proper glycosylation ensures functional protein distribution and cellular communication.

3. Single Correct Answer MCQ: Golgi-derived vesicles primarily:
(A) Produce ATP
(B) Transport modified proteins
(C) Replicate DNA
(D) Generate mechanical support
Explanation: Correct answer is (B). Golgi packages modified proteins into vesicles that transport them to plasma membrane, lysosomes, or secretory pathways. Vesicular transport is critical for secretion and intracellular trafficking. ATP production is a mitochondrial function, DNA replication occurs in the nucleus, and mechanical support is provided by cytoskeleton. Golgi vesicles ensure correct delivery of functional proteins and lipids, maintaining cellular homeostasis and efficient molecular trafficking.

4. Single Correct Answer MCQ: Which organelle does not participate in energy production?
(A) Golgi apparatus
(B) Mitochondria
(C) Chloroplasts
(D) Cytoplasm (glycolysis)
Explanation: Correct answer is (A). Golgi apparatus is involved in processing and packaging proteins and lipids, not ATP generation. Mitochondria produce cellular energy via oxidative phosphorylation, chloroplasts generate ATP in photosynthesis, and cytoplasm carries out glycolysis. Recognizing non-energetic roles of Golgi is essential for understanding cellular compartmentalization, organelle specialization, and molecular trafficking in eukaryotic cells.

5. Single Correct Answer MCQ: Golgi apparatus is directly connected with:
(A) Ribosomes on rough ER
(B) Mitochondria
(C) Lysosomes
(D) Cytoskeleton
Explanation: Correct answer is (A). Golgi receives proteins from rough ER, modifies them, and dispatches via vesicles to lysosomes, plasma membrane, or secretion. It is not structurally or functionally connected to mitochondria for energy, lysosomes for degradation, or cytoskeleton for support. The ER-Golgi network ensures coordinated processing and trafficking, highlighting organelle interaction for post-translational modifications and precise delivery of cellular macromolecules.

6. Single Correct Answer MCQ: Golgi cisternae are:
(A) DNA-containing
(B) Flattened membranous sacs
(C) Tubular extensions
(D) ATP-producing
Explanation: Correct answer is (B). Golgi cisternae are stacked flattened membrane sacs where proteins and lipids undergo modification, sorting, and packaging. Tubular extensions facilitate vesicle budding, but the main structure is flattened. DNA is not present; ATP is not produced. Understanding cisternal structure clarifies mechanism of molecular processing, vesicle formation, and trafficking within the secretory pathway of eukaryotic cells.

7. Assertion-Reason MCQ:
Assertion (A): Golgi apparatus modifies proteins from ER.
Reason (R): Proteins synthesized on rough ER are transported to Golgi for post-translational modifications.
(A) Both A and R are true, and R is the correct explanation of A
(B) Both A and R are true, but R is not the correct explanation of A
(C) A is true, R is false
(D) A is false, R is true
Explanation: Option (A) is correct. Proteins synthesized on rough ER are transported to Golgi apparatus for glycosylation, sulfation, and packaging. This post-translational modification ensures functional maturation before secretion or targeting to specific cellular compartments. Understanding this ER-Golgi relationship is fundamental for cellular biology, protein trafficking, and secretion pathways in eukaryotic cells.

8. Matching Type MCQ: Match organelle with function:
1. Golgi apparatus    A. ATP production
2. Mitochondria    B. Protein modification and sorting
3. Lysosome    C. Cellular digestion
4. Ribosome    D. Protein synthesis
(A) 1-B, 2-A, 3-C, 4-D
(B) 1-A, 2-B, 3-D, 4-C
(C) 1-B, 2-D, 3-A, 4-C
(D) 1-D, 2-C, 3-B, 4-A
Explanation: Correct option is 1-B, 2-A, 3-C, 4-D. Golgi modifies and sorts proteins (1-B), mitochondria generate ATP (2-A), lysosomes digest cellular components (3-C), ribosomes synthesize proteins (4-D). Matching organelles to functions clarifies cell organization, molecular trafficking, and functional specialization. Golgi’s role is central in post-translational modification, vesicular transport, and secretion pathways in eukaryotic cells.

9. Fill in the Blanks / Completion MCQ: Golgi apparatus is the site of ______ formation.
(A) Glycoprotein and glycolipid
(B) ATP
(C) mRNA
(D) Ion channels
Explanation: Glycoprotein and glycolipid is correct. Golgi apparatus processes and modifies proteins and lipids received from rough ER, forming glycoproteins and glycolipids essential for cell membrane, signaling, and secretion. It does not produce ATP or mRNA, nor form ion channels. Understanding Golgi’s biosynthetic function emphasizes its central role in molecular modification, cellular trafficking, and membrane composition, critical for proper cell function and intercellular communication.

10. Choose the correct statements MCQ:
Statement I: Golgi apparatus modifies ER-synthesized proteins.
Statement II: Golgi produces cellular energy in the form of ATP.
(A) Only Statement I is correct
(B) Only Statement II is correct
(C) Both I and II are correct
(D) Neither I nor II is correct
Explanation: Option (A) is correct. Golgi apparatus modifies and sorts proteins synthesized on rough ER, adding carbohydrates or lipids for functional maturation. It does not produce ATP; that is the role of mitochondria. Correct identification of organelle functions highlights compartmentalization, protein processing, and secretory pathway organization, fundamental to cell biology and understanding the intracellular logistics of macromolecule handling in eukaryotic cells.

Topic: Endomembrane System; Subtopic: Organelles Not Part of Endomembrane System

Lead Question - 2023

Which of the following are NOT considered as the part of endomembrane system?
(A) Mitochondria
(B) Endoplasmic Reticulum
(C) Chloroplasts
(D) Golgi complex
(E) Peroxisomes
Choose the most appropriate answer from the options given below:
(1) A and D only
(2) A, C and E only
(3) B and D only
(4) A, D and E only

Answer: (2) A, C and E only. Mitochondria, chloroplasts, and peroxisomes are not part of the endomembrane system. The endomembrane system includes organelles like endoplasmic reticulum and Golgi complex, which are interconnected via membrane trafficking, vesicles, and cisternal flow, facilitating synthesis, modification, and transport of proteins and lipids. Mitochondria and chloroplasts have double membranes and their own DNA, functioning independently. Peroxisomes are single-membrane organelles involved in detoxification but do not communicate via vesicles with other endomembrane organelles. Hence, A, C, and E are excluded from the endomembrane system.

Keyword Definitions:

• Mitochondria: Double-membraned organelle, site of ATP production, independent from endomembrane system.

• Chloroplasts: Plant organelle, photosynthesis occurs here, has its own DNA, not part of endomembrane system.

• Peroxisomes: Single-membrane organelle involved in detoxification and lipid metabolism, not connected by vesicles.

• Endoplasmic Reticulum (ER): Network of membranes, involved in protein and lipid synthesis, part of endomembrane system.

• Golgi complex: Organelle that modifies, sorts, and packages proteins and lipids, part of endomembrane system.

• Endomembrane system: A group of interrelated organelles that communicate via vesicles for transport of biomolecules.

• Vesicle: Small membrane-bound structure for transporting molecules between endomembrane organelles.

• Cisternal flow: Movement of membranes and contents through Golgi cisternae.

1. Single Correct Answer:

Which organelle is responsible for protein synthesis and is part of endomembrane system?
(1) Mitochondria
(2) Endoplasmic Reticulum
(3) Chloroplasts
(4) Peroxisomes

Answer: (2) Endoplasmic Reticulum. Rough ER is studded with ribosomes, synthesizes proteins destined for secretion, membranes, or lysosomes, and communicates with Golgi via vesicles, making it an integral part of the endomembrane system.

2. Single Correct Answer:

Which organelle modifies and packages proteins for secretion?
(1) Golgi complex
(2) Mitochondria
(3) Peroxisomes
(4) Chloroplasts

Answer: (1) Golgi complex. Proteins synthesized in ER are transported via vesicles to Golgi, where they are modified, sorted, and packaged for secretion or targeting to organelles.

3. Single Correct Answer:

Which of the following is independent of vesicle transport?
(1) Golgi complex
(2) Peroxisomes
(3) ER
(4) Lysosomes

Answer: (2) Peroxisomes. Unlike ER or Golgi, peroxisomes are single-membrane organelles that function independently, do not form part of vesicular endomembrane system, and are involved in detoxification and lipid metabolism.

4. Single Correct Answer:

Which organelle has its own DNA and is not part of endomembrane system?
(1) ER
(2) Mitochondria
(3) Golgi complex
(4) Lysosome

Answer: (2) Mitochondria. Mitochondria have double membranes, independent DNA, and reproduce autonomously, hence are not integrated into endomembrane system despite being vital for energy metabolism.

5. Single Correct Answer:

Which organelle detoxifies hydrogen peroxide and other toxins?
(1) ER
(2) Peroxisomes
(3) Golgi complex
(4) Lysosome

Answer: (2) Peroxisomes. These organelles contain enzymes like catalase that decompose hydrogen peroxide and other toxic compounds. They function independently and are not part of endomembrane system.

6. Single Correct Answer:

Which plant organelle is double-membraned and independent of endomembrane system?
(1) Golgi complex
(2) Chloroplasts
(3) ER
(4) Vacuole

Answer: (2) Chloroplasts. Chloroplasts have double membranes, contain their own DNA, and perform photosynthesis independently, not forming part of vesicle-mediated endomembrane system.

7. Assertion-Reason:

Assertion A: Golgi complex is part of endomembrane system.
Reason R: Golgi communicates via vesicles with ER and lysosomes.
(1) A true, R false
(2) A false, R true
(3) Both true, R explains A
(4) Both true, R does not explain A

Answer: (3) Both true, R explains A. The Golgi modifies, sorts, and packages proteins from ER, forming part of endomembrane system, connected via vesicular transport.

8. Matching Type:

Match organelles with features:
List I | List II
A. ER | I. Protein and lipid synthesis
B. Golgi | II. Modification and packaging
C. Mitochondria | III. ATP production
D. Peroxisomes | IV. Detoxification
Options:
(1) A-I, B-II, C-III, D-IV
(2) A-II, B-I, C-IV, D-III
(3) A-III, B-IV, C-I, D-II
(4) A-IV, B-III, C-II, D-I

Answer: (1) A-I, B-II, C-III, D-IV. ER synthesizes proteins and lipids, Golgi modifies and packages, mitochondria produce ATP, peroxisomes detoxify substances.

9. Fill in the Blanks:

_________ is a single-membrane organelle involved in detoxification and is not part of endomembrane system.
Options: (1) ER (2) Golgi complex (3) Peroxisome (4) Lysosome

Answer: (3) Peroxisome. It removes hydrogen peroxide and other toxic compounds independently.

10. Choose the correct statements:

Statement I: ER and Golgi are connected via vesicles.
Statement II: Mitochondria and chloroplasts are part of endomembrane system.
Options:
(1) I true, II false
(2) I false, II true
(3) Both true
(4) Both false

Answer: (1) I true, II false. ER and Golgi communicate through vesicles forming the endomembrane system. Mitochondria and chloroplasts are independent organelles and not part of this system.

Topic: Cytoskeleton; Subtopic: Functions of Cytoskeleton

Lead Question - 2023

Which of the following functions is carried out by cytoskeleton in a cell?
(1) Motility
(2) Transportation
(3) Nuclear division
(4) Protein synthesis

Answer: (1) Motility. The cytoskeleton provides structural support and facilitates motility, intracellular transport, and organization of organelles. It consists of microfilaments, intermediate filaments, and microtubules. Microfilaments enable movement and shape changes, microtubules guide vesicle transport, and intermediate filaments provide mechanical strength. The cytoskeleton also plays a crucial role in mitosis and meiosis by forming the mitotic spindle. Protein synthesis occurs in ribosomes and is not a direct function of cytoskeleton. Therefore, cytoskeleton’s primary cellular functions involve maintaining architecture, intracellular transport, signal transduction, and motility.

Keyword Definitions:

• Cytoskeleton: Network of protein filaments providing structure and motility to cells.

• Microfilaments: Thin filaments composed of actin, involved in cell shape and motility.

• Intermediate Filaments: Fibrous proteins providing mechanical strength to cells.

• Microtubules: Hollow tubes guiding vesicle transport and forming mitotic spindle.

• Motility: Ability of cells or organelles to move.

• Intracellular Transport: Movement of organelles and vesicles within a cell.

• Nuclear Division: Process of mitosis or meiosis involving chromosome segregation.

1. Single Correct Answer:

Which cytoskeletal component is primarily responsible for cell movement?
(1) Microtubules
(2) Microfilaments
(3) Intermediate filaments
(4) Ribosomes

Answer: (2) Microfilaments. Actin-based microfilaments drive motility through lamellipodia and filopodia formation, allowing cells to migrate, change shape, and perform phagocytosis.

2. Single Correct Answer:

Which cytoskeletal element forms the mitotic spindle?
(1) Microfilaments
(2) Microtubules
(3) Intermediate filaments
(4) Actin

Answer: (2) Microtubules. Microtubules assemble into the mitotic spindle during mitosis and meiosis, facilitating accurate chromosome segregation and nuclear division.

3. Single Correct Answer:

Which cytoskeletal component provides mechanical stability to cells?
(1) Microfilaments
(2) Microtubules
(3) Intermediate filaments
(4) Ribosomes

Answer: (3) Intermediate filaments. They resist mechanical stress and maintain cell integrity by forming a resilient network throughout the cytoplasm.

4. Single Correct Answer:

Intracellular vesicle transport is mainly mediated by:
(1) Microfilaments
(2) Microtubules
(3) Intermediate filaments
(4) Nucleus

Answer: (2) Microtubules. They serve as tracks for motor proteins like kinesin and dynein to transport vesicles, organelles, and other cargo within the cell.

5. Single Correct Answer:

Which of the following is NOT a function of cytoskeleton?
(1) Cell motility
(2) Organelle positioning
(3) Protein synthesis
(4) Nuclear division

Answer: (3) Protein synthesis. Protein synthesis occurs in ribosomes, whereas the cytoskeleton organizes cell structure, facilitates transport, and assists in nuclear division.

6. Single Correct Answer:

Which cytoskeletal filaments are composed of actin?
(1) Microtubules
(2) Microfilaments
(3) Intermediate filaments
(4) Myosin filaments

Answer: (2) Microfilaments. Actin filaments enable shape changes, motility, phagocytosis, and cortical tension in eukaryotic cells.

7. Assertion-Reason:

Assertion A: Cytoskeleton is involved in intracellular transport.
Reason R: Microtubules serve as tracks for motor proteins like kinesin and dynein.
(1) A true, R false
(2) A false, R true
(3) Both true, R explains A
(4) Both true, R does not explain A

Answer: (3) Both true, R explains A. Microtubules act as highways for motor proteins, enabling vesicle, organelle, and protein complex transport across the cell efficiently.

8. Matching Type:

Match cytoskeletal element with its function:
List I | List II
A. Microfilaments | I. Mechanical strength
B. Microtubules | II. Motility and shape
C. Intermediate filaments | III. Vesicle transport
Options:
(1) A-II, B-III, C-I
(2) A-III, B-II, C-I
(3) A-I, B-III, C-II
(4) A-II, B-I, C-III

Answer: (1) A-II, B-III, C-I. Microfilaments enable motility, microtubules transport vesicles, and intermediate filaments provide mechanical support.

9. Fill in the Blanks:

The cytoskeletal component responsible for vesicle and organelle transport is _______.
Options: (1) Microfilaments (2) Microtubules (3) Intermediate filaments (4) Ribosomes

Answer: (2) Microtubules. Microtubules serve as tracks for kinesin and dynein motors, enabling efficient intracellular transport of vesicles and organelles.

10. Choose Correct Statements:

Statement I: Microfilaments are composed of actin.
Statement II: Protein synthesis occurs within the cytoskeleton.
Options:
(1) Both true
(2) I true, II false
(3) I false, II true
(4) Both false

Answer: (2) I true, II false. Microfilaments are actin-based and contribute to motility, while protein synthesis occurs in ribosomes, not the cytoskeleton.

Chapter: Cell Biology; Topic: Ribosomes; Subtopic: Structure and Function of Ribosomes

Keyword Definitions:

• Ribosome: Cellular organelle composed of rRNA and proteins, responsible for protein synthesis.

• Proteins: Organic macromolecules composed of amino acids, performing structural, enzymatic, and regulatory functions in cells.

• rRNA: Ribosomal RNA, a major component of ribosomes that catalyzes peptide bond formation.

• Translation: Process of synthesizing proteins from mRNA in the ribosome.

• Subunits: Ribosomes consist of small and large subunits made of rRNA and proteins.

• Polypeptides: Chains of amino acids that fold into functional proteins.

• Prokaryotic Ribosome: 70S ribosome made of 30S and 50S subunits.

• Eukaryotic Ribosome: 80S ribosome composed of 40S and 60S subunits.

• Functional Ribosome: Site where mRNA is translated into amino acid sequences.

• Ribosomal Proteins: Proteins that stabilize rRNA and assist in ribosome assembly.

• Translation Machinery: Collective components of ribosome and associated factors required for protein synthesis.

Lead Question - 2023:

How many different proteins does a ribosome consist of ?
(1) 40
(2) 20
(3) 80
(4) 60

Answer & Explanation: (4) 60. Eukaryotic ribosomes are composed of two subunits, 40S (small) and 60S (large), together forming an 80S ribosome. The ribosome contains approximately 60 different proteins that stabilize rRNA structure and assist in ribosome assembly and function. Ribosomal proteins are essential for proper translation of mRNA into polypeptides. In prokaryotes, the ribosome is smaller (70S) with 52 proteins. Thus, in eukaryotic ribosomes, the total number of distinct proteins is about 60, not 40, 20, or 80, while rRNA forms the catalytic core.

1. Ribosomes synthesize proteins by:
(1) DNA replication
(2) Transcription
(3) Translation
(4) Splicing
Explanation: Ribosomes translate mRNA sequences into polypeptides, assembling amino acids into proteins. Correct answer is (3).

2. Ribosomal subunits in eukaryotes are:
(1) 30S and 50S
(2) 40S and 60S
(3) 50S and 70S
(4) 20S and 40S
Explanation: Eukaryotic ribosomes consist of 40S small and 60S large subunits, forming an 80S ribosome. Correct answer is (2).

3. Ribosomal RNA functions to:
(1) Transport proteins
(2) Catalyze peptide bond formation
(3) Store genetic information
(4) Degrade mRNA
Explanation: rRNA catalyzes peptide bond formation between amino acids during protein synthesis. Correct answer is (2).

4. Prokaryotic ribosomes are composed of:
(1) 40S and 60S
(2) 30S and 50S
(3) 50S and 60S
(4) 20S and 30S
Explanation: Prokaryotic ribosomes are 70S, made of 30S small and 50S large subunits. Correct answer is (2).

5. Ribosomal proteins are required for:
(1) DNA synthesis
(2) Ribosome assembly and stabilization
(3) Lipid metabolism
(4) Membrane transport
Explanation: Ribosomal proteins stabilize rRNA structure and facilitate assembly of functional ribosomes for translation. Correct answer is (2).

6. Ribosome size “S” unit refers to:
(1) Volume
(2) Sedimentation rate
(3) Molecular weight
(4) Length
Explanation: “S” denotes Svedberg units, a measure of sedimentation rate during ultracentrifugation, reflecting size and density. Correct answer is (2).

Assertion-Reason Type Question
7. Assertion (A): Eukaryotic ribosomes are larger than prokaryotic ribosomes.
Reason (R): They contain more rRNA and proteins than prokaryotic ribosomes.
(1) Both A and R true, R explains A
(2) Both A and R true, R does not explain A
(3) A true, R false
(4) A false, R true
Explanation: Eukaryotic 80S ribosomes are larger than prokaryotic 70S ribosomes because they have more rRNA and about 60 proteins, compared to 52 in prokaryotes. Correct answer is (1).

Matching Type Question
8. Match:
A. 40S subunit – (i) Small eukaryotic subunit
B. 60S subunit – (ii) Large eukaryotic subunit
C. 30S subunit – (iii) Small prokaryotic subunit
D. 50S subunit – (iv) Large prokaryotic subunit
(1) A-(i), B-(ii), C-(iii), D-(iv)
(2) A-(ii), B-(i), C-(iv), D-(iii)
(3) A-(iii), B-(iv), C-(i), D-(ii)
(4) A-(iv), B-(iii), C-(ii), D-(i)
Explanation: Eukaryotic small and large subunits are 40S and 60S; prokaryotic small and large are 30S and 50S. Correct answer is (1).

Fill in the Blanks Question
9. Ribosome catalyzes the formation of _______ bonds during translation.
(1) Peptide
(2) Glycosidic
(3) Phosphodiester
(4) Hydrogen
Explanation: Ribosomes catalyze peptide bond formation between amino acids to form polypeptides. Correct answer is (1).

Choose the Correct Statements Question
10. Statement I: Ribosomal proteins are essential for ribosome function.
Statement II: Ribosomes contain DNA as structural component.
(1) Both I and II correct
(2) Only I correct
(3) Only II correct
(4) Neither I nor II correct
Explanation: Ribosomal proteins are required for ribosome assembly and translation (I correct). Ribosomes do not contain DNA; they consist of rRNA and proteins.

Chapter: Cell Biology; Topic: Lysosomes and Cellular Digestion; Subtopic: Lysosomal Function and pH Dependence

Keyword Definitions:

• Lysosome: A membrane-bound organelle containing hydrolytic enzymes for digestion of macromolecules.

• Hydrolytic Enzymes: Enzymes that catalyze the breakdown of biomolecules by hydrolysis.

• pH: Measure of hydrogen ion concentration; determines acidity or alkalinity.

• Alkaline pH: pH greater than 7, less acidic environment.

• Acidic Environment: Low pH; necessary for optimal lysosomal enzyme activity.

• Autophagy: Process by which cells digest their own components via lysosomes.

• Endocytosis: Uptake of extracellular material that can be degraded in lysosomes.

• Enzyme Inactivation: Loss of enzyme activity due to unfavorable conditions such as pH changes.

• Cytoplasm: Cell fluid where organelles are suspended.

• Lysosomal Storage Disorders: Diseases caused by defective lysosomal enzymes.

• Membrane Integrity: Maintenance of lysosome structure prevents enzyme leakage.

Lead Question - 2022 (Ganganagar)

If the pH in lysosomes is increased to alkaline, what will be the outcome?

1. Hydrolytic enzymes will function more efficiently

2. Hydrolytic enzymes will become inactive

3. Lysosomal enzymes will be released into the cytoplasm

4. Lysosomal enzymes will be more active

Explanation: Lysosomal hydrolytic enzymes are acid hydrolases that require an acidic environment (pH ~4.5–5) for activity. Raising the pH to alkaline conditions reduces the proton concentration, causing these enzymes to lose their catalytic efficiency and become inactive. As a result, macromolecule degradation within lysosomes is inhibited, leading to accumulation of undigested material. The lysosomal membrane remains intact unless damaged, so enzyme release into the cytoplasm does not normally occur solely due to pH change. Correct answer is 2. Maintaining acidic pH is crucial for lysosomal function and proper cellular digestion.

1. Single Correct Answer MCQ:

Which organelle contains hydrolytic enzymes for intracellular digestion?

a) Mitochondria

b) Lysosome

c) Endoplasmic reticulum

d) Golgi apparatus

Explanation: Lysosomes contain hydrolytic enzymes that degrade macromolecules and cellular debris. They function optimally at acidic pH. Correct answer is b. Other organelles have different primary functions such as energy production (mitochondria) and protein processing (ER and Golgi).

2. Single Correct Answer MCQ:

Optimal pH for lysosomal enzyme activity is:

a) Neutral (7)

b) Acidic (~4.5–5)

c) Alkaline (~8)

d) Slightly basic (~7.5)

Explanation: Lysosomal enzymes are acid hydrolases and function best in acidic conditions, around pH 4.5–5. Correct answer is b. Alkaline or neutral pH reduces enzyme activity.

3. Single Correct Answer MCQ:

If lysosomal pH increases, which of the following occurs?

a) Increased degradation

b) Enzyme inactivation

c) Enhanced autophagy

d) Increased energy production

Explanation: Alkalinization of lysosomes inactivates hydrolytic enzymes, preventing degradation of cellular components. Correct answer is b. Energy production occurs in mitochondria, not lysosomes.

4. Single Correct Answer MCQ:

Which process is directly affected by lysosomal enzyme inactivation?

a) Protein synthesis

b) Autophagy

c) Glycolysis

d) DNA replication

Explanation: Autophagy relies on active lysosomal enzymes to degrade organelles and macromolecules. Enzyme inactivation due to alkaline pH impairs autophagy. Correct answer is b.

5. Single Correct Answer MCQ:

Lysosomal storage disorders may result from:

a) Increased lysosomal acidity

b) Enzyme deficiency

c) High cytoplasmic ATP

d) Excessive ribosome activity

Explanation: Defective lysosomal enzymes or altered pH prevents degradation of macromolecules, causing lysosomal storage disorders. Correct answer is b.

6. Single Correct Answer MCQ:

Which is true regarding lysosomal membrane integrity?

a) Alkaline pH ruptures the membrane

b) Membrane prevents enzyme leakage under normal conditions

c) Acidic pH damages the membrane

d) Membrane is unnecessary for enzyme function

Explanation: Lysosomal membranes contain hydrolytic enzymes safely. Alkaline pH inactivates enzymes but does not automatically rupture the membrane. Correct answer is b.

7. Assertion-Reason MCQ:

Assertion (A): Lysosomal enzymes stop functioning at alkaline pH.

Reason (R): Hydrolytic enzymes require acidic conditions for activity.

a) Both A and R true, R explains A

b) Both A and R true, R does not explain A

c) A true, R false

d) A false, R true

Explanation: Both assertion and reason are correct; the acidic environment is necessary for hydrolytic activity. Correct answer is a.

8. Matching Type MCQ:

Match List-I with List-II:

List-I | List-II

(a) Lysosome | (i) Contains hydrolytic enzymes

(b) Mitochondria | (ii) Produces ATP

(c) Golgi apparatus | (iii) Protein modification and packaging

(d) Endoplasmic reticulum | (iv) Protein and lipid synthesis

Options:

1. a-i, b-ii, c-iii, d-iv

2. a-ii, b-i, c-iv, d-iii

3. a-iii, b-iv, c-i, d-ii

4. a-iv, b-iii, c-ii, d-i

Explanation: Correct matches: lysosome (i), mitochondria (ii), Golgi (iii), ER (iv). Correct answer is 1.

9. Fill in the Blanks / Completion MCQ:

Hydrolytic enzymes in lysosomes function optimally at _______ pH.

a) Neutral

b) Acidic

c) Alkaline

d) Variable

Explanation: Lysosomal enzymes are acid hydrolases requiring acidic pH (~4.5–5) for activity. Correct answer is b.

10. Choose the correct statements MCQ (Statement I & II):

Statement I: Lysosomal enzymes are inactivated in alkaline conditions.

Statement II: Lysosomal membranes rupture automatically when pH rises.

a) Both I and II correct

b) Only I correct

c) Only II correct

d) Both incorrect

Explanation: Statement I is correct; alkaline pH inactivates enzymes. Statement II is incorrect; membranes remain intact under normal pH changes. Correct answer is b. 

Topic: Amphibolic Pathway and Energy Metabolism ; Subtopic: Role of Porins, Leghemoglobin, and H+ Accumulation

Keyword Definitions:

• Porins: Large protein channels present in the outer membrane of mitochondria that allow free movement of small molecules like ions and metabolites.

• Leghemoglobin: An oxygen-binding pigment found in root nodules of leguminous plants that facilitates oxygen supply to nitrogen-fixing bacteria.

• Thylakoid: Membranous sacs in chloroplasts where light-dependent reactions occur, leading to H+ accumulation inside their lumen.

• Amphibolic Pathway: A biochemical pathway that functions both catabolically and anabolically, like the Krebs cycle in respiration.

• Respiration: A cellular process that converts biochemical energy from nutrients into ATP, involving glycolysis, Krebs cycle, and electron transport chain.

Lead Question – 2022 (Ganganagar)
Match List-I with List-II:
List-I            List-II
(a) Porins            (i) Pink coloured nodules
(b) Leghemoglobin       (ii) Lumen of thylakoid
(c) H+ Accumulation      (iii) Amphibolic pathway
(d) Respiration          (iv) Huge pores in outer membrane of mitochondria

Choose the correct answer from the options given below:
(a) (b) (c) (d)
1. (ii) (i) (iv) (iii)
2. (iv) (i) (ii) (iii)
3. (iii) (iv) (ii) (i)
4. (ii) (iv) (i) (iii)

Explanation:
The correct answer is option 2: (a)–(iv), (b)–(i), (c)–(ii), (d)–(iii). Porins are large protein pores in the outer mitochondrial membrane allowing metabolite transport. Leghemoglobin is a pink pigment in root nodules aiding nitrogen fixation. H+ accumulation occurs in thylakoid lumen during photosynthesis, and respiration is an amphibolic pathway involving both energy release and biosynthesis.

1. Single Correct Answer Type
Porins are mainly present in which organelle of eukaryotic cells?
1. Chloroplast
2. Mitochondrion
3. Nucleus
4. Ribosome
Explanation: Porins are large protein channels found in the outer mitochondrial membrane, allowing free passage of small metabolites like ATP, ADP, and ions. They maintain exchange between the cytosol and mitochondria, supporting respiration and energy metabolism. Thus, option 2 is correct, as mitochondria contain porins for efficient transport regulation.

2. Single Correct Answer Type
Leghemoglobin plays an important role in nitrogen fixation by:
1. Releasing oxygen to bacteria
2. Preventing oxygen poisoning of nitrogenase
3. Acting as a carbon source
4. Providing ATP for nitrogenase
Explanation: Leghemoglobin binds oxygen, maintaining a low but steady oxygen concentration inside root nodules. This prevents oxygen inhibition of nitrogenase enzyme while ensuring respiratory ATP synthesis for nitrogen fixation. Hence, option 2 is correct, as leghemoglobin acts as an oxygen buffer promoting efficient nitrogen fixation in legumes.

3. Single Correct Answer Type
H+ accumulation in the lumen of thylakoids occurs during:
1. Glycolysis
2. Light-dependent reactions
3. Calvin cycle
4. Photorespiration
Explanation: During light-dependent reactions of photosynthesis, protons (H+) accumulate inside the thylakoid lumen due to water splitting and electron transport chain activity. This proton gradient drives ATP synthesis through ATP synthase in photophosphorylation. Hence, option 2 is correct as it explains proton motive force formation during photosynthetic reactions.

4. Single Correct Answer Type
Which of the following statements about respiration is true?
1. It is only a catabolic process.
2. It produces ATP without oxidation.
3. It is an amphibolic process.
4. It occurs only in plants.
Explanation: Respiration is an amphibolic process as it functions both catabolically (breaking down glucose to release energy) and anabolically (providing intermediates for biosynthesis). The Krebs cycle acts as a central link between metabolism and biosynthesis. Hence, option 3 is correct as respiration integrates both anabolic and catabolic roles.

5. Single Correct Answer Type
The pink color of root nodules in leguminous plants is due to:
1. Anthocyanin
2. Chlorophyll
3. Leghemoglobin
4. Carotenoid
Explanation: Leghemoglobin, a red-colored oxygen-binding protein similar to animal hemoglobin, imparts a pink coloration to root nodules in leguminous plants. It regulates oxygen supply to nitrogen-fixing bacteria, preventing nitrogenase inactivation. Thus, option 3 is correct as leghemoglobin plays a dual role in oxygen management and symbiotic nitrogen fixation.

6. Single Correct Answer Type
Which of the following is known as the site of oxidative phosphorylation?
1. Thylakoid membrane
2. Mitochondrial inner membrane
3. Cytoplasm
4. Nuclear envelope
Explanation: Oxidative phosphorylation occurs on the inner mitochondrial membrane, where the electron transport chain operates to generate ATP. The proton gradient across this membrane drives ATP synthesis via ATP synthase. Therefore, option 2 is correct, representing mitochondria as the powerhouse of the cell responsible for energy production.

7. Assertion-Reason Type
Assertion (A): Respiration is both a catabolic and anabolic pathway.
Reason (R): Intermediates of the Krebs cycle participate in biosynthesis of amino acids and fats.
1. Both (A) and (R) are correct and (R) explains (A).
2. Both (A) and (R) are correct but (R) does not explain (A).
3. (A) is correct but (R) is incorrect.
4. (A) is incorrect but (R) is correct.
Explanation: Respiration is an amphibolic process since its intermediates such as α-ketoglutarate and oxaloacetate act as precursors for biosynthetic pathways. Hence, both (A) and (R) are correct and (R) properly explains (A). The correct answer is option 1, showing integration of energy and biosynthesis in metabolism.

8. Matching Type
Match the organelle with its function:
A. Mitochondria – (i) ATP synthesis
B. Chloroplast – (ii) Photosynthesis
C. Nucleus – (iii) Genetic control
D. Ribosome – (iv) Protein synthesis
Options:
1. A-(i), B-(ii), C-(iii), D-(iv)
2. A-(ii), B-(i), C-(iv), D-(iii)
3. A-(iii), B-(ii), C-(i), D-(iv)
4. A-(iv), B-(iii), C-(ii), D-(i)
Explanation: Mitochondria produce ATP, chloroplasts carry out photosynthesis, nucleus stores genetic material, and ribosomes synthesize proteins. Hence, option 1 is correct, as each organelle performs a unique but interrelated role in maintaining cellular energy, metabolism, and regulation essential for life processes.

9. Fill in the Blanks Type
Porins are present in the _______ membrane of mitochondria.
1. Inner
2. Outer
3. Cristae
4. Matrix
Explanation: Porins are located in the outer membrane of mitochondria, forming large aqueous channels that allow diffusion of ions and metabolites. They facilitate communication between the cytosol and mitochondrial intermembrane space. Hence, option 2 is correct, as outer membrane porins are essential for metabolic exchange and transport regulation.

10. Choose the Correct Statements Type
Statement I: H+ accumulation occurs in the lumen of thylakoids during light reaction.
Statement II: Respiration is exclusively a catabolic pathway.
1. Both statements are correct.
2. Both statements are incorrect.
3. Statement I is correct, Statement II is incorrect.
4. Statement I is incorrect, Statement II is correct.
Explanation: H+ accumulation indeed occurs inside the thylakoid lumen during light reactions of photosynthesis, while respiration is an amphibolic pathway, not purely catabolic. Hence, Statement I is correct and Statement II is incorrect. The correct answer is option 3, explaining both processes’ functional interdependence in cellular metabolism.

Subtopic: Types of Cell Junctions and Their Functions

Keyword Definitions:

• Adhering Junctions: Also called desmosomes, these junctions fasten cells together into strong sheets, maintaining tissue structure under mechanical stress.

• Tight Junctions: Form impermeable barriers that prevent leakage of extracellular molecules across layers of cells.

• Gap Junctions: Channels connecting the cytoplasm of adjacent cells, allowing passage of ions and small molecules for cell-to-cell communication.

• Synaptic Junctions: Specialized junctions in neurons where neurotransmitters transmit signals from one neuron to another across synapses.

• Cell Communication: The process by which cells exchange information via chemical or electrical signals.

• Extracellular Matrix: Network of molecules surrounding cells providing structural and biochemical support.

• Neurotransmitters: Chemical messengers released by neurons to transmit signals across synaptic junctions.

Lead Question – 2022 (Abroad)
Match List-I with List-II
List-I
(a) Adhering junctions
(b) Tight junction
(c) Gap junctions
(d) Synaptic junctions
List-II
(i) Establish a barrier that prevents leakage of extracellular fluid across a layer of cells
(ii) Functions like rivets and fasten cells junctions together into strong sheets
(iii) Pass information through neurotransmitters from one cell to another
(iv) Provide cytoplasmic channels from one cell to an adjacent cell for communication
Choose the correct answer from the options given below:
1. (iv), (iii), (ii), (i)
2. (i), (iii), (ii), (iv)
3. (ii), (i), (iv), (iii)
4. (i), (ii), (iii), (iv)

Explanation:
Correct answer is option 3. Adhering junctions act like rivets, fastening cells together into strong sheets to maintain tissue integrity. Tight junctions establish impermeable barriers, preventing leakage of extracellular fluid. Gap junctions provide cytoplasmic channels for communication between adjacent cells. Synaptic junctions transmit signals using neurotransmitters from one neuron to another. These four types of junctions are essential for tissue structure, intercellular communication, and signal transduction. Understanding their distinct roles helps explain how cells coordinate function in multicellular organisms. The correct matching ensures each junction type is paired with its precise function, as demonstrated in option 3.

1. Which junction type allows direct cytoplasmic exchange between adjacent cells?
1. Adhering junction
2. Tight junction
3. Gap junction
4. Synaptic junction
Explanation: Correct answer is gap junction. Gap junctions provide cytoplasmic channels connecting adjacent cells, enabling passage of ions, nutrients, and signaling molecules for rapid communication. They are crucial for synchronized activity in cardiac and smooth muscle tissues, and other cellular networks.

2. Which junction prevents leakage of molecules across epithelial layers?
1. Gap junction
2. Tight junction
3. Adhering junction
4. Synaptic junction
Explanation: Correct answer is tight junction. Tight junctions seal adjacent epithelial cells, creating a barrier to prevent the movement of ions, water, and other molecules between cells. This is vital for tissue compartmentalization and maintaining homeostasis across epithelial layers.

3. Which junction provides mechanical strength by linking cells into sheets?
1. Tight junction
2. Synaptic junction
3. Adhering junction
4. Gap junction
Explanation: Correct answer is adhering junction. Adhering junctions, also called desmosomes, act like rivets fastening cells together, distributing mechanical stress across tissue sheets. They are particularly important in epithelial tissues and cardiac muscle where structural stability is required.

4. Which junction is specialized for neuron-to-neuron signaling?
1. Gap junction
2. Adhering junction
3. Tight junction
4. Synaptic junction
Explanation: Correct answer is synaptic junction. Synaptic junctions are chemical synapses where neurotransmitters are released from the presynaptic neuron and received by postsynaptic receptors. This allows rapid, directional communication essential for neural network function and signal propagation.

5. Which junction type is critical for synchronized contraction in cardiac tissue?
1. Adhering junction
2. Gap junction
3. Tight junction
4. Synaptic junction
Explanation: Correct answer is gap junction. Gap junctions in cardiac muscle allow ions to flow directly between cells, facilitating synchronized contraction of the heart muscle. This electrical coupling ensures efficient and coordinated heartbeat.

6. Which junction is also called desmosome?
1. Tight junction
2. Adhering junction
3. Gap junction
4. Synaptic junction
Explanation: Correct answer is adhering junction. Desmosomes are specialized adhering junctions that link the cytoskeletons of adjacent cells via cadherin proteins, providing mechanical strength and resistance to tissue stress.

7. Assertion-Reason:
Assertion (A): Tight junctions are crucial for maintaining compartmentalization in tissues.
Reason (R): They prevent leakage of extracellular fluid between cells.
1. Both A and R are true, R explains A
2. Both A and R are true, R does not explain A
3. A true, R false
4. A false, R true
Explanation: Correct answer is option 1. Tight junctions prevent extracellular leakage, thereby maintaining distinct compartments across epithelial and endothelial layers. This explains why they are crucial for tissue integrity and functional compartmentalization.

8. Matching Type:
Match the junction with its main component:
A. Adhering junction – (i) Cadherins
B. Tight junction – (ii) Claudins and Occludins
C. Gap junction – (iii) Connexins
D. Synaptic junction – (iv) Neurotransmitters
1. A–i, B–ii, C–iii, D–iv
2. A–ii, B–i, C–iv, D–iii
3. A–iii, B–iv, C–i, D–ii
4. A–iv, B–iii, C–ii, D–i
Explanation: Correct answer is option 1. Adhering junctions use cadherins for adhesion, tight junctions use claudins/occludins for sealing, gap junctions are formed by connexins, and synaptic junctions rely on neurotransmitters for signal transmission.

9. Fill in the Blanks:
________ junctions function as rivets to fasten cells into strong sheets.
1. Gap
2. Tight
3. Adhering
4. Synaptic
Explanation: Correct answer is adhering. Adhering junctions mechanically link adjacent cells via cadherins and cytoskeletal elements, forming strong cellular sheets, especially in epithelial and cardiac tissues. They help maintain tissue integrity under mechanical stress.

10. Choose the correct statements:
Statement I: Gap junctions allow direct communication between cells.

Chapter: Cell Organelles; Topic: Plastids and Their Functions; Subtopic: Types of Plastids

Keyword Definitions:

• Chromoplasts: Plastids containing pigments like carotenoids, responsible for red, orange, or yellow colors in fruits and flowers.

• Amyloplasts: Non-pigmented plastids that store starch granules in roots and tubers.

• Elaioplasts: Colorless plastids specialized for storing oils and fats.

• Aleuroplasts: Protein-storing plastids found in seeds.

• Starch: Polysaccharide used as energy storage in plants.

• Carotene: Orange pigment found in chromoplasts.

• Oil and Fats: Lipid molecules stored in elaioplasts for energy.

• Proteins: Macromolecules stored in aleuroplasts, providing nutrients for seed germination.

Lead Question – 2022 (Abroad)
Match List-I with List-II:
List-I
(a) Chromoplasts
(b) Amyloplasts
(c) Elaioplasts
(d) Aleuroplasts
List-II
(i) Proteins
(ii) Oil and fats
(iii) Starch
(iv) Carotene
Choose the correct answer from the options below:
1. (iv) (i) (iii) (ii)
2. (iv) (iii) (ii) (i)
3. (iv) (ii) (iii) (i)
4. (iv) (iii) (i) (ii)

Explanation:
Correct answer is option 4. Chromoplasts contain pigments like carotene (iv), responsible for red, orange, or yellow coloration in fruits and flowers. Amyloplasts store starch granules (iii) as energy reserves in roots and tubers. Elaioplasts are specialized for storing oils and fats (ii). Aleuroplasts store proteins (i), providing nutrients for seed germination. This classification of plastids demonstrates functional specialization, with different types of plastids contributing to storage, coloration, or metabolism in plants. Matching List-I to List-II helps in understanding plastid roles in plant physiology and adaptation to ecological functions.

1. Which plastid is responsible for storing starch in plants?
1. Chromoplasts
2. Amyloplasts
3. Elaioplasts
4. Aleuroplasts
Explanation: Correct answer is Amyloplasts. Amyloplasts are non-pigmented plastids specialized for storing starch granules in roots, tubers, and seeds. They play a key role in energy storage and metabolism, providing a source of glucose for plant growth and germination. Unlike chromoplasts, they do not contain pigments, and unlike elaioplasts or aleuroplasts, they store carbohydrates rather than lipids or proteins.

2. Which plastid contains carotenoid pigments for coloration?
1. Amyloplasts
2. Chromoplasts
3. Elaioplasts
4. Aleuroplasts
Explanation: Correct answer is Chromoplasts. Chromoplasts are plastids containing carotenoid pigments such as carotene, giving yellow, orange, or red coloration to fruits and flowers. These pigments attract pollinators and aid in seed dispersal. Chromoplasts differ from chloroplasts, which contain chlorophyll for photosynthesis, and from storage plastids like amyloplasts or elaioplasts that store starch or lipids.

3. Elaioplasts primarily store:
1. Carotenoids
2. Proteins
3. Starch
4. Oils and fats
Explanation: Correct answer is Oils and fats. Elaioplasts are colorless plastids specialized in lipid storage, providing energy for seed germination and metabolic processes. They are abundant in oil-rich seeds. Unlike amyloplasts storing starch or aleuroplasts storing proteins, elaioplasts focus on lipid accumulation, highlighting plastid functional specialization in plants.

4. Aleuroplasts are specialized for storing:
1. Carotenoids
2. Proteins
3. Starch
4. Lipids
Explanation: Correct answer is Proteins. Aleuroplasts are protein-storing plastids found in seeds, providing nutrients during germination. They are distinct from amyloplasts (starch), chromoplasts (pigments), and elaioplasts (lipids). Their stored proteins supply amino acids for early growth of seedlings, ensuring proper development.

5. Which of the following plastids contributes to fruit coloration?
1. Aleuroplasts
2. Elaioplasts
3. Chromoplasts
4. Amyloplasts
Explanation: Correct answer is Chromoplasts. Chromoplasts contain pigments such as carotene that impart yellow, orange, or red colors to fruits and flowers. This coloration aids in attracting pollinators and seed dispersers. Unlike storage plastids (amyloplasts, elaioplasts, aleuroplasts), chromoplasts function primarily in pigmentation rather than nutrient storage.

6. Which plastid is colorless and stores starch?
1. Chromoplast
2. Amyloplast
3. Elaioplast
4. Aleuroplast
Explanation: Correct answer is Amyloplast. Amyloplasts are non-pigmented plastids storing starch granules. They provide an energy reserve for plants, especially in roots and tubers. Being colorless distinguishes them from chromoplasts and chloroplasts. Their specialization exemplifies plastid diversity for specific plant functions.

7. Assertion-Reason:
Assertion (A): Chromoplasts are responsible for coloration in fruits and flowers.
Reason (R): Chromoplasts contain carotenoid pigments like carotene.
1. Both A and R are true, R is correct explanation of A
2. Both A and R are true, R is not correct explanation
3. A is true, R is false
4. A is false, R is true
Explanation: Correct answer is option 1. Chromoplasts contain carotenoids such as carotene, responsible for red, orange, and yellow colors in fruits and flowers. This pigmentation attracts pollinators and aids in seed dispersal. The reason explains the function stated in the assertion, demonstrating the link between pigment content and coloration.

8. Matching Type:
Match List-I (Plastids) with List-II (Contents):
A. Chromoplast – (i) Carotene
B. Amyloplast – (ii) Starch
C. Elaioplast – (iii) Oil and fats
D. Aleuroplast – (iv) Proteins
1. A–i, B–ii, C–iii, D–iv
2. A–ii, B–i, C–iv, D–iii
3. A–i, B–iii, C–ii, D–iv
4. A–iv, B–ii, C–i, D–iii
Explanation: Correct answer is option 1. Chromoplasts store carotene, amyloplasts store starch, elaioplasts store oils and fats, and aleuroplasts store proteins. This matching clarifies the functional diversity of plastids and their role in storage and pigmentation in plant tissues.

9. Fill in the Blanks:
Plastids that store __________ are called elaioplasts.
1. Starch
2. Carotenoids
3. Oils and fats
4. Proteins
Explanation: Correct answer is Oils and fats. Elaioplasts are colorless plastids specialized in lipid storage, providing energy for seed germination. They are distinct from amyloplasts (starch), chromoplasts (pigments), and aleuroplasts (proteins). Their presence in seeds and fruits ensures energy availability for early growth.

10. Choose the correct statements:
Statement I: Amyloplasts are non-pigmented plastids storing starch.
Statement II:</

Topic: Endomembrane System; Subtopic: Membrane-bound Organelles

Keyword Definitions:

• Endomembrane System: Network of membrane-bound organelles including ER, Golgi apparatus, lysosomes, and vesicles, coordinating cellular functions.

• Membrane-bound Organelles: Cellular structures surrounded by lipid bilayers that compartmentalize different biochemical processes.

• Mitochondria: Double-membrane organelle responsible for ATP production through oxidative phosphorylation, not part of the endomembrane system.

• Chloroplasts: Double-membrane organelle in plants and algae that performs photosynthesis, also not part of the endomembrane system.

• Endoplasmic Reticulum (ER): Organelle of the endomembrane system involved in protein and lipid synthesis.

• Golgi Apparatus: Organelle modifying, sorting, and packaging proteins and lipids from the ER.

• Lysosomes: Vesicles containing hydrolytic enzymes for intracellular digestion, part of the endomembrane system.

• Vesicles: Membrane-bound sacs transporting materials between organelles and plasma membrane.

Lead Question - 2022 (Abroad)
Given below are two statements :
Statement - I : Membrane-bound organelles of the endomembrane system coordinate cellular functions.
Statement - II : Mitochondria and chloroplasts are not considered a part of the endomembrane system.
In the light of the above statements, choose the most appropriate answer from the options given below:
1. Statement - I is correct but Statement - II is incorrect
2. Statement - I is incorrect but Statement - II is correct
3. Both Statement - I and Statement - II are correct
4. Both Statement - I and Statement - II are incorrect
Explanation: The correct answer is Both Statement - I and Statement - II are correct. The endomembrane system includes ER, Golgi apparatus, lysosomes, and vesicles, which coordinate cellular processes such as protein and lipid trafficking, and intracellular digestion. Mitochondria and chloroplasts are double-membrane organelles with independent DNA and ribosomes, carrying out energy conversion and photosynthesis. They are functionally and structurally distinct from the endomembrane system. Therefore, Statement I correctly describes the coordination role of the endomembrane system, and Statement II correctly identifies that mitochondria and chloroplasts are excluded from this system, highlighting key organizational principles of eukaryotic cells.

1. Single Correct Answer Type:
Which organelle modifies and packages proteins synthesized in the ER?
1. Lysosome
2. Golgi Apparatus
3. Mitochondria
4. Chloroplast
Explanation: The correct answer is Golgi Apparatus. Proteins synthesized in the endoplasmic reticulum are transported to the Golgi apparatus in vesicles, where they undergo modification, sorting, and packaging for secretion or delivery to other organelles. Lysosomes degrade macromolecules, mitochondria produce ATP, and chloroplasts perform photosynthesis. This system ensures proper trafficking and functionality of proteins and lipids, essential for maintaining cellular organization and endomembrane system efficiency in eukaryotic cells.

2. Single Correct Answer Type:
Which of the following organelles is part of the endomembrane system?
1. Mitochondria
2. Chloroplast
3. Lysosome
4. Peroxisome
Explanation: The correct answer is Lysosome. Lysosomes are membrane-bound organelles containing hydrolytic enzymes and are integral to the endomembrane system, receiving proteins and lipids from the ER and Golgi apparatus for intracellular digestion. Mitochondria and chloroplasts are double-membrane organelles with their own DNA and ribosomes, performing energy conversion and photosynthesis. Peroxisomes are not classically part of the endomembrane system. Lysosomes play a central role in cellular homeostasis, recycling macromolecules, and coordinating with other endomembrane components.

3. Single Correct Answer Type:
Which organelle stores calcium and participates in lipid synthesis as part of the endomembrane system?
1. Rough ER
2. Smooth ER
3. Mitochondria
4. Chloroplast
Explanation: The correct answer is Smooth ER. Smooth endoplasmic reticulum is a membrane-bound organelle of the endomembrane system involved in lipid synthesis, detoxification, and calcium storage. Rough ER is associated with protein synthesis. Mitochondria and chloroplasts are energy-related organelles with their own DNA and ribosomes, not part of the endomembrane system. Smooth ER interacts with other organelles like Golgi and vesicles, facilitating coordinated cellular functions and maintaining the biochemical compartmentalization characteristic of the endomembrane system.

4. Single Correct Answer Type:
Which statement correctly describes mitochondria and chloroplasts?
1. Part of endomembrane system
2. Double-membrane organelles with independent DNA
3. Synthesize proteins for lysosomes
4. Store digestive enzymes
Explanation: The correct answer is Double-membrane organelles with independent DNA. Mitochondria and chloroplasts contain their own circular DNA and ribosomes, enabling semi-autonomous protein synthesis. They are not part of the endomembrane system. Their double-membrane structure distinguishes them from ER, Golgi, and lysosomes. They are responsible for energy conversion, ATP production in mitochondria, and photosynthesis in chloroplasts. Their unique features support endosymbiotic theory, explaining the evolutionary origin of eukaryotic cells and their compartmentalized organelles.

5. Single Correct Answer Type:
Which vesicles transport proteins from ER to Golgi apparatus?
1. Lysosomes
2. Transport Vesicles
3. Peroxisomes
4. Endosomes
Explanation: The correct answer is Transport Vesicles. Transport vesicles are membrane-bound sacs that bud off from the endoplasmic reticulum and carry newly synthesized proteins to the Golgi apparatus for modification and sorting. Lysosomes degrade macromolecules, peroxisomes metabolize fatty acids, and endosomes mediate endocytosis. Transport vesicles are central to the endomembrane system, ensuring proper delivery of proteins, maintaining cellular homeostasis, and coordinating inter-organelle communication essential for eukaryotic cell functionality.

6. Single Correct Answer Type:
Which organelle receives and digests macromolecules in the endomembrane system?
1. Lysosome
2. Smooth ER
3. Mitochondria
4. Chloroplast
Explanation: The correct answer is Lysosome. Lysosomes contain hydrolytic enzymes to digest macromolecules delivered via endocytosis or from intracellular organelles. They are part of the endomembrane system, interacting with Golgi-derived vesicles. Smooth ER participates in lipid synthesis and calcium storage, mitochondria in ATP production, and chloroplasts in photosynthesis. Lysosomes maintain cellular homeostasis, recycle biomolecules, and enable coordinated intracellular processes with other endomembrane organelles.

7. Assertion-Reason Type:
Assertion (A): The endomembrane system coordinates intracellular transport.
Reason (R): Mitochondria and chloroplasts are independent and not included in the endomembrane system.
1. Both A and R are correct, and R is the correct explanation of A
2. Both A and R are correct, but R is not the correct explanation of A
3. A is correct, R is false
4. A is false, R is true
Explanation: Correct answer is Both A and R are correct, and R is the correct explanation of A. The endomembrane system, comprising ER, Golgi, lysosomes, and vesicles, coordinates protein and lipid transport. Mitochondria and chloroplasts are double-membrane organelles with their own DNA and ribosomes, functioning independently in energy conversion, and thus are excluded. Their independence highlights the specialization of the endomembrane system in intracellular trafficking and compartmentalization of biochemical processes in eukaryotic cells.

8. Matching Type:
Match the organelle with its function:
A. Rough ER → (i) Lipid synthesis
B. Smooth ER → (ii) Protein synthesis
C. Golgi apparatus → (iii) Modification and sorting of proteins
D. Lysosome → (iv) Intracellular digestion
1. A-(ii), B-(i), C-(iii), D-(iv)
2. A-(i), B-(ii), C-(iv), D-(iii)
3. A-(iii), B-(ii), C-(i), D-(iv)
4. A-(ii), B-(iii), C-(iv), D-(i)
Explanation: Correct answer is A-(ii), B-(i), C-(iii), D-(iv). Rough ER has ribosomes for protein synthesis; smooth ER synthesizes lip

Topic: Endoplasmic Reticulum (ER)
Subtopic: Types and Functions of ER

Keyword Definitions:
• Endoplasmic Reticulum (ER): A membranous organelle in eukaryotic cells forming a network of tubules and sacs.
• Smooth ER (SER): ER lacking ribosomes, involved in lipid synthesis, detoxification, and calcium storage.
• Rough ER (RER): ER with ribosomes on its surface, site of protein synthesis and modification.
• Ribosomes: Cellular structures that synthesize proteins using mRNA template.
• Lipid Synthesis: Biochemical process of producing fats and phospholipids in SER.
• Prokaryotes: Organisms lacking nucleus and membrane-bound organelles.
• Eukaryotes: Cells with nucleus and membrane-bound organelles including ER.
• Detoxification: Removal or modification of toxic substances in cells.
• Protein Modification: Post-translational processes in RER for proper folding and transport.
• Calcium Storage: SER stores calcium ions important for cellular signaling.

Lead Question (2022):
Which of the following statements with respect to Endoplasmic Reticulum is incorrect ?
(1) SER is devoid of ribosomes
(2) In prokaryotes only RER are present
(3) SER are the sites for lipid synthesis
(4) RER has ribosomes attached to ER

Explanation: The correct answer is (2). Prokaryotic cells lack membrane-bound organelles including both SER and RER. Only eukaryotic cells contain ER. SER lacks ribosomes and is involved in lipid synthesis, whereas RER has ribosomes attached for protein synthesis, making option (2) factually incorrect.

Guessed MCQs:

1. Single Correct Answer:
Which ER is responsible for detoxification and carbohydrate metabolism?
(a) RER
(b) SER
(c) Both RER and SER
(d) Golgi apparatus
Explanation: The correct answer is (b). Smooth ER (SER) detoxifies drugs and harmful substances and participates in carbohydrate metabolism. Its lack of ribosomes differentiates it from RER, which is primarily responsible for protein synthesis and processing.

2. Single Correct Answer:
Which ER has ribosomes attached to it for protein synthesis?
(a) SER
(b) RER
(c) Golgi apparatus
(d) Lysosome
Explanation: The correct answer is (b). Rough ER (RER) has ribosomes attached to its cytoplasmic surface. These ribosomes translate mRNA into proteins, which are folded and modified in RER before transport to Golgi or other destinations.

3. Single Correct Answer:
Lipid synthesis mainly occurs in:
(a) SER
(b) RER
(c) Mitochondria
(d) Nucleus
Explanation: The correct answer is (a). Smooth ER (SER) is the main site of lipid synthesis, including phospholipids and steroids, essential for cell membrane formation, hormone production, and storage, distinguishing its function from RER.

4. Assertion-Reason MCQ:
Assertion (A): RER is studded with ribosomes.
Reason (R): RER is primarily involved in lipid synthesis.
(a) Both A and R are correct and R explains A
(b) Both A and R are correct but R does not explain A
(c) A is correct, R is false
(d) A is false, R is true
Explanation: The correct answer is (c). RER is correctly studded with ribosomes; however, its primary function is protein synthesis, not lipid synthesis, which occurs in SER. Hence, the reason is incorrect.

5. Single Correct Answer:
Which statement is true regarding SER?
(a) Contains ribosomes
(b) Participates in lipid synthesis
(c) Present in prokaryotes
(d) Synthesizes proteins
Explanation: The correct answer is (b). Smooth ER (SER) lacks ribosomes, is absent in prokaryotes, and primarily participates in lipid synthesis, detoxification, and calcium storage, distinguishing it from RER.

6. Single Correct Answer:
Which type of cell contains ER?
(a) Prokaryotic cells
(b) Eukaryotic cells
(c) Bacterial cells
(d) Archaeal cells
Explanation: The correct answer is (b). Only eukaryotic cells contain membrane-bound organelles including ER. Prokaryotic cells lack ER and other organelles such as mitochondria and Golgi apparatus.

7. Fill in the Blanks:
The _______ is involved in synthesis of steroid hormones and detoxification.
(a) SER
(b) RER
(c) Lysosome
(d) Nucleus
Explanation: The correct answer is (a). Smooth ER (SER) synthesizes lipids including steroid hormones and detoxifies xenobiotics, playing a crucial role in cellular metabolism.

8. Single Correct Answer:
Which ER is more prominent in cells producing large amounts of protein?
(a) RER
(b) SER
(c) Golgi apparatus
(d) Mitochondria
Explanation: The correct answer is (a). Cells that synthesize large amounts of protein, such as pancreatic cells, have extensive RER. The ribosomes attached to RER enable high protein production and secretion.

9. Single Correct Answer:
Which feature differentiates RER from SER?
(a) Presence of ribosomes
(b) Lipid synthesis
(c) Calcium storage
(d) Detoxification
Explanation: The correct answer is (a). The presence of ribosomes on the cytoplasmic surface is the primary structural feature distinguishing RER from SER. SER lacks ribosomes and has different functions like lipid synthesis and detoxification.

10. Choose the correct statements:
(a) SER lacks ribosomes
(b) RER is studded with ribosomes
(c) SER is site of protein synthesis
(d) RER is absent in prokaryotes
Options:
1. a, b, d only
2. a and c only
3. b and c only
4. All statements
Explanation: The correct answer is (1). SER lacks ribosomes (a), RER has ribosomes (b), and RER is absent in prokaryotes (d). Statement (c) is incorrect because protein synthesis occurs in RER, not SER.

Topic: Structure of Chromosomes
Subtopic: Types of Chromosomes Based on Centromere Position

Keyword Definitions:

• Chromosome: Thread-like structure made of DNA and proteins carrying genetic information.

• Centromere: The constricted region of a chromosome where spindle fibers attach during cell division.

• Metacentric Chromosome: Centromere lies in the middle forming two equal arms.

• Sub-metacentric Chromosome: Centromere slightly away from the center forming unequal arms.

• Acrocentric Chromosome: Centromere near one end forming one long and one short arm.

• Telocentric Chromosome: Centromere located at the terminal end, forming a single arm.

Lead Question (2022):
Match List–I with List–II.
List – I           List – II
(a) Metacentric           (i) Centromere situated close to the end forming one extremely short and one very long arm
(b) Acrocentric           (ii) Centromere at the terminal end
(c) Sub-metacentric           (iii) Centromere in the middle forming equal arms
(d) Telocentric           (iv) Centromere slightly away from the middle forming unequal arms
(1) (a)-(i), (b)-(iii), (c)-(ii), (d)-(iv)
(2) (a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)
(3) (a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)
(4) (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)

Explanation: Metacentric chromosomes have centromere in the middle, sub-metacentric slightly away from the center, acrocentric near the end, and telocentric at the terminal end. Hence, the correct answer is (3) (a)-(iii), (b)-(i), (c)-(iv), (d)-(ii).

1. Guessed Question:
The centromere is located exactly in the middle in:
(1) Acrocentric chromosome
(2) Metacentric chromosome
(3) Sub-metacentric chromosome
(4) Telocentric chromosome

Explanation: In metacentric chromosomes, the centromere lies in the center forming two equal arms, giving a ‘V’ shape during anaphase. Hence, the correct answer is (2) Metacentric chromosome.

2. Guessed Question:
Which type of chromosome has the centromere near one end, producing one short and one long arm?
(1) Telocentric
(2) Metacentric
(3) Sub-metacentric
(4) Acrocentric

Explanation: Acrocentric chromosomes have the centromere near one end, resulting in one extremely short and one long arm, forming a ‘J’ shape. Hence, the correct answer is (4) Acrocentric.

3. Guessed Question:
Sub-metacentric chromosomes have arms that are:
(1) Equal in length
(2) Unequal in length
(3) Without arms
(4) Circular in structure

Explanation: Sub-metacentric chromosomes have the centromere slightly away from the center, forming one shorter and one longer arm. Hence, the correct answer is (2) Unequal in length.

4. Guessed Question:
Telocentric chromosomes are found in:
(1) Humans
(2) Mice
(3) Plants only
(4) Bacteria

Explanation: Telocentric chromosomes have centromeres at the terminal end, forming only one arm. They are common in mice but not in humans. Hence, the correct answer is (2) Mice.

5. Guessed Question:
Which chromosome type appears ‘V’-shaped during anaphase?
(1) Metacentric
(2) Sub-metacentric
(3) Acrocentric
(4) Telocentric

Explanation: Metacentric chromosomes have centromeres in the middle, resulting in a V-shape during anaphase movement as both arms are equal. Hence, the correct answer is (1) Metacentric.

6. Guessed Question:
The term “centromere” refers to:
(1) End region of chromosome
(2) Primary constriction region
(3) Tip of the chromatid
(4) Region where crossing over occurs

Explanation: Centromere is the primary constriction on a chromosome that holds sister chromatids together and attaches to spindle fibers during cell division. Hence, the correct answer is (2) Primary constriction region.

7. Assertion-Reason Question:
Assertion (A): The shape of a chromosome during anaphase depends on centromere position.
Reason (R): The centromere attaches to spindle fibers, pulling chromatids apart.
(1) Both A and R are true, and R explains A.
(2) Both A and R are true, but R does not explain A.
(3) A is true, R is false.
(4) A is false, R is true.

Explanation: Chromosome shape at anaphase (V, L, J, or I) is determined by centromere position. Centromeres connect spindle fibers for separation. Hence, both statements are true, and R explains A. The correct answer is (1).

8. Matching Type Question:
Match chromosome type with its shape at anaphase:
A. Metacentric — (i) V-shaped
B. Sub-metacentric — (ii) L-shaped
C. Acrocentric — (iii) J-shaped
D. Telocentric — (iv) I-shaped
(1) A–i, B–ii, C–iii, D–iv
(2) A–ii, B–i, C–iv, D–iii
(3) A–iii, B–iv, C–i, D–ii
(4) A–iv, B–iii, C–ii, D–i

Explanation: Metacentric chromosomes are V-shaped, sub-metacentric L-shaped, acrocentric J-shaped, and telocentric I-shaped. Hence, the correct answer is (1) A–i, B–ii, C–iii, D–iv.

9. Fill in the Blanks:
The position of the ______ determines the shape of chromosomes during ______.
(1) Nucleolus, prophase
(2) Centromere, anaphase
(3) Spindle fiber, metaphase
(4) Chromatid, telophase

Explanation: Centromere position decides the shape of chromosomes at anaphase. V, L, J, or I shapes appear based on centromere location. Hence, the correct answer is (2) Centromere, anaphase.

10. Choose the Correct Statements:
(a) Centromere position determines chromosome type.
(b) Metacentric chromosomes form equal arms.
(c) Telocentric chromosomes have no short arm.
(d) Acrocentric chromosomes form equal arms.
(1) (a), (b), and (c) only
(2) (b) and (d) only
(3) (a), (c), and (d) only
(4) (a), (b), and (d) only

Explanation: Centromere position defines chromosome type. Metacentric chromosomes have equal arms, telocentric lack short arm, while acrocentric have unequal arms. Hence, the correct answer is (1) (a), (b), and (c) only.

Topic: Molecular Genetics
Subtopic: Chromatin Structure and Nucleosome

Keyword Definitions:

• Euchromatin: Loosely packed chromatin that is transcriptionally active and accessible for RNA synthesis.

• Heterochromatin: Densely packed chromatin that is usually transcriptionally inactive.

• Histone octamer: Protein complex of eight histone molecules around which DNA wraps to form a nucleosome.

• DNA: Negatively charged nucleic acid that wraps around histones to form chromatin.

• Histones: Positively charged proteins rich in lysine and arginine that help package DNA.

• Nucleosome: Basic structural unit of chromatin, consisting of DNA wrapped around a histone octamer.

• Base pairs (bp): Pair of complementary nucleotides in DNA; 1 bp ≈ 0.34 nm in length.

• Transcriptionally active: Regions of DNA being actively transcribed into RNA.

• Transcriptionally inactive: DNA regions that are tightly packed and not transcribed.

• Chromatin: Complex of DNA and protein found in eukaryotic cells.

Lead Question (2022)
Read the following statements and choose the set of correct statements:
(a) Euchromatin is loosely packed chromatin
(b) Heterochromatin is transcriptionally active
(c) Histone octomer is wrapped by negatively charged DNA in nucleosome
(d) Histones are rich in lysine and arginine
(e) A typical nucleosome contains 400 bp of DNA helix
(1) (a), (c), (d) only
(2) (b), (e) only
(3) (a), (c), (e) only
(4) (b), (d), (e) only

Explanation:
Euchromatin is loosely packed and transcriptionally active, heterochromatin is inactive. DNA wraps around histone octamer, and histones are rich in lysine and arginine. A typical nucleosome contains approximately 146 bp, not 400 bp. Correct statements are (a), (c), and (d). Therefore, the correct answer is (1).

1. Single Correct Answer MCQ:
Which chromatin type is transcriptionally inactive?
(1) Euchromatin
(2) Heterochromatin
(3) Nucleosome
(4) Histone octamer

Explanation:
Heterochromatin is densely packed and transcriptionally inactive, whereas euchromatin is active. Nucleosome is the structural unit of chromatin, and histone octamer is a protein complex, not a chromatin type. Correct answer is (2).

2. Single Correct Answer MCQ:
The histone proteins are rich in which amino acids?
(1) Lysine and Arginine
(2) Glycine and Serine
(3) Alanine and Valine
(4) Aspartate and Glutamate

Explanation:
Histones are basic proteins rich in positively charged lysine and arginine residues, which interact with negatively charged DNA to form nucleosomes. Other amino acids like glycine, alanine, or acidic residues do not predominate in histones. Correct answer is (1).

3. Single Correct Answer MCQ:
Approximately how many base pairs of DNA wrap around a histone octamer in a nucleosome?
(1) 146 bp
(2) 400 bp
(3) 50 bp
(4) 1000 bp

Explanation:
Each nucleosome contains DNA wrapped around histone octamer, about 146 base pairs long. Option 400 bp is incorrect. This wrapping helps compact DNA and regulate gene expression. Correct answer is (1).

4. Single Correct Answer MCQ:
Which statement about euchromatin is correct?
(1) It is transcriptionally inactive
(2) It is loosely packed
(3) It is rich in heterochromatin
(4) It contains 400 bp DNA

Explanation:
Euchromatin is loosely packed and transcriptionally active, allowing gene expression. It is not heterochromatin, nor does it contain exactly 400 bp DNA. Correct answer is (2).

5. Single Correct Answer MCQ:
DNA wraps around histone octamer due to:
(1) DNA being positively charged
(2) Histones being negatively charged
(3) Histones being positively charged
(4) Hydrophobic interactions only

Explanation:
DNA is negatively charged due to phosphate backbone. Histones are positively charged, rich in lysine and arginine, enabling electrostatic interactions that wrap DNA around histone octamers to form nucleosomes. Correct answer is (3).

6. Single Correct Answer MCQ:
Heterochromatin is generally found:
(1) In actively transcribed regions
(2) At centromeres and telomeres
(3) Loosely packed
(4) Wrapped around histone H1 only

Explanation:
Heterochromatin is densely packed, transcriptionally inactive, and commonly located at centromeres and telomeres, contributing to chromosome stability. Euchromatin is active and loosely packed. Correct answer is (2).

7. Assertion-Reason MCQ:
Assertion (A): Nucleosome formation compacts DNA
Reason (R): DNA is negatively charged and wraps around positively charged histones
Options:
(1) Both A and R correct and R explains A
(2) A correct, R incorrect
(3) A incorrect, R correct
(4) Both incorrect

Explanation:
Nucleosome formation compacts DNA in chromatin, and the negative DNA wraps around positively charged histones due to electrostatic interactions. Both statements are correct, and the reason explains the assertion. Correct answer is (1).

8. Matching Type MCQ:
Match component with property:
A. Histone octamer — 1. 146 bp DNA wrapped
B. Nucleosome — 2. Eight histone proteins
C. Euchromatin — 3. Loosely packed, transcriptionally active
D. Heterochromatin — 4. Densely packed, transcriptionally inactive
Options:
(1) A–2, B–1, C–3, D–4
(2) A–1, B–2, C–4, D–3
(3) A–3, B–4, C–1, D–2
(4) A–2, B–1, C–4, D–3

Explanation:
Histone octamer: eight histone proteins (A–2), Nucleosome: 146 bp DNA wrapped (B–1), Euchromatin: loosely packed active (C–3), Heterochromatin: densely packed inactive (D–4). Correct answer is (1).

9. Fill in the Blanks:
Transcriptionally inactive chromatin is called ________.
(1) Euchromatin
(2) Heterochromatin
(3) Nucle

Topic: Chromatin Structure
Subtopic: Histones

Keyword Definitions:

• Histones: Proteins around which DNA winds to form nucleosomes in chromatin.

• Lysine and Arginine: Positively charged amino acids abundant in histones.

• Nucleosome: Structural unit of chromatin consisting of DNA wrapped around 8 histone proteins.

• Chromatin: Complex of DNA and proteins in the nucleus.

• Positive charge: Enables histones to bind negatively charged DNA phosphate backbone.

• Acidic pH: Incorrect for histones; they are basic due to positive amino acids.

Lead Question - 2021

Which one of the following statements about Histones is wrong?

(1) The pH of histones is slightly acidic
(2) Histones are rich in amino acids Lysine and Arginine
(3) Histones carry positive charge in the side chain
(4) Histones are organized to form a unit of 8 molecules

Explanation: Histones are basic proteins, rich in lysine and arginine, carrying positive charges, and organized as octamers (8 molecules) in nucleosomes. The statement about acidic pH is incorrect. Correct answer is option (1) The pH of histones is slightly acidic.

1. Which histone is not part of the core octamer in nucleosomes?
(1) H2A
(2) H2B
(3) H3
(4) H1
Explanation: Histone H1 is not part of the nucleosome core octamer; it acts as a linker histone stabilizing DNA between nucleosomes. H2A, H2B, H3, and H4 form the octamer core. Correct answer is option (4) H1.

2. Histones bind to DNA primarily because:
(1) DNA is positively charged
(2) DNA is negatively charged
(3) Histones are hydrophobic
(4) Histones are acidic
Explanation: DNA has a negatively charged phosphate backbone, which attracts positively charged histone proteins rich in lysine and arginine. This electrostatic interaction facilitates nucleosome formation. Correct answer is option (2) DNA is negatively charged.

3. The basic amino acids in histones are:
(1) Glutamate and Aspartate
(2) Lysine and Arginine
(3) Phenylalanine and Tyrosine
(4) Serine and Threonine
Explanation: Lysine and Arginine are basic amino acids present in histones, providing positive charges that bind negatively charged DNA. Glutamate and aspartate are acidic, phenylalanine/tyrosine are aromatic, and serine/threonine are polar uncharged. Correct answer is option (2) Lysine and Arginine.

4. Nucleosomes are formed by wrapping DNA around:
(1) H1 only
(2) H2A-H2B and H3-H4 octamer
(3) H1-H3 only
(4) H2B-H4 dimer
Explanation: Nucleosomes are DNA wrapped around an octamer of histones: two molecules each of H2A, H2B, H3, and H4. H1 is a linker histone not in the core octamer. Correct answer is option (2) H2A-H2B and H3-H4 octamer.

5. Histone modification that relaxes chromatin is:
(1) Methylation
(2) Acetylation
(3) Phosphorylation
(4) Ubiquitination
Explanation: Acetylation of lysine residues on histone tails neutralizes positive charges, reducing DNA binding and relaxing chromatin structure, facilitating transcription. Methylation can repress or activate, phosphorylation and ubiquitination have regulatory roles. Correct answer is option (2) Acetylation.

6. Which histone is involved in higher-order chromatin folding?
(1) H2A
(2) H2B
(3) H3
(4) H1
Explanation: Histone H1 is the linker histone that binds DNA between nucleosomes and is essential for higher-order chromatin folding into 30 nm fibers. Core histones (H2A, H2B, H3, H4) form the nucleosome. Correct answer is option (4) H1.

7. Assertion-Reason Question:
Assertion (A): Histones are rich in lysine and arginine.
Reason (R): These amino acids give histones a positive charge enabling DNA binding.
(1) Both A and R are true, R is correct explanation of A
(2) Both A and R are true, R is not correct explanation of A
(3) A true, R false
(4) A false, R true
Explanation: Histones are indeed rich in lysine and arginine. These basic amino acids provide positive charges which allow electrostatic interaction with negatively charged DNA. Both statements are true and the reason correctly explains the assertion. Correct answer is option (1).

8. Matching Type Question:
Match histone types with function:
(a) H2A/H2B - 1. Linker histone
(b) H3/H4 - 2. Nucleosome core
(c) H1 - 3. Stabilizes linker DNA
(1) a-2, b-2, c-3
(2) a-1, b-2, c-3
(3) a-2, b-1, c-3
(4) a-3, b-2, c-1
Explanation: H2A/H2B and H3/H4 form nucleosome core (a-2, b-2). H1 is linker histone stabilizing DNA between nucleosomes (c-3). Correct answer is option (1).

9. Fill in the Blanks:
The ________ histone binds between nucleosomes and helps in higher-order chromatin structure.
(1) H2A
(2) H2B
(3) H3
(4) H1
Explanation: Histone H1 is the linker histone that binds between nucleosomes, facilitating higher-order chromatin folding. H2A, H2B, H3 are core nucleosome histones. Correct answer is option (4) H1.

10. Choose the correct statements:
(a) Histones are basic proteins.
(b) DNA wraps around histone octamers.
(c) Histones are acidic in nature.
(d) H1 is a linker histone.
(1) a, b, d
(2) a, c, d
(3) b, c, d
(4) a, b, c
Explanation: Histones are basic proteins (a), DNA wraps around octamers (b), and H1 is a linker histone (d). They are not acidic. Correct answer is option (1) a, b, d.

Topic: Cell Organelles

Subtopic: Endomembrane System

• Endomembrane System: A network of membranes within the cell involved in protein and lipid transport.

• Endoplasmic Reticulum (ER): Organelle that synthesizes proteins (rough ER) and lipids (smooth ER).

• Golgi Complex: Organelle that modifies, sorts, and packages proteins and lipids for transport.

• Lysosomes: Membrane-bound organelles containing digestive enzymes for macromolecule breakdown.

• Vacuoles: Membrane-bound sacs used for storage and transport within the cell.

• Mitochondria: Organelle responsible for ATP production via oxidative phosphorylation.

• Ribosomes: Protein-synthesizing structures, not part of endomembrane system.

• Membrane-bound Organelles: Organelles enclosed by a lipid bilayer.

• Protein Transport: Movement of proteins between organelles in the cell.

• Intracellular Trafficking: Transport of molecules within the cell via vesicles and membranes.

• Secretory Pathway: ER-Golgi network for processing and delivering proteins outside the cell.

Lead Question - 2021

The organelles that are included in the endomembrane system are:

Options:
1. Endoplasmic reticulum, Golgi complex, Lysosomes and Vacuoles
2. Golgi complex, Mitochondria, Ribosomes and Lysosomes
3. Golgi complex, Endoplasmic reticulum, Mitochondria and Lysosomes
4. Endoplasmic reticulum, Mitochondria, Ribosomes and Lysosomes

Explanation: The endomembrane system includes organelles involved in synthesis, modification, and transport of proteins and lipids: Endoplasmic reticulum, Golgi complex, lysosomes, and vacuoles. Mitochondria and ribosomes are not part of this system. Answer: Endoplasmic reticulum, Golgi complex, Lysosomes and Vacuoles.

1. Which organelle is responsible for protein modification and packaging?
Options:
A. Endoplasmic reticulum
B. Golgi complex
C. Lysosomes
D. Vacuoles

Explanation: The Golgi complex modifies, sorts, and packages proteins and lipids synthesized by the endoplasmic reticulum for transport within and outside the cell. Lysosomes and vacuoles serve different functions. Answer: Golgi complex.

2. Which organelle contains digestive enzymes for breaking down macromolecules?
Options:
A. Golgi complex
B. Lysosomes
C. Vacuoles
D. Mitochondria

Explanation: Lysosomes are membrane-bound organelles that contain hydrolytic enzymes for digestion of cellular waste and macromolecules. They are part of the endomembrane system. Answer: Lysosomes.

3. Smooth ER is mainly involved in:
Options:
A. Protein synthesis
B. Lipid synthesis
C. ATP production
D. DNA replication

Explanation: Smooth ER synthesizes lipids and detoxifies certain chemicals. Rough ER synthesizes proteins, and mitochondria produce ATP. DNA replication occurs in the nucleus. Answer: Lipid synthesis.

4. Which organelle stores substances and helps in intracellular transport?
Options:
A. Vacuoles
B. Lysosomes
C. Golgi complex
D. Ribosomes