Biomolecules

Topic: Proteins

Subtopic: Peptide Bond Formation

• Amino Acid: Organic molecule containing amino (-NH2) and carboxyl (-COOH) groups; building blocks of proteins.

• Carboxyl Group: Functional group (-COOH) present in amino acids involved in peptide bond formation.

• Amino Group: Functional group (-NH2) in amino acids that reacts with carboxyl group to form peptide bonds.

• Peptide Bond: Covalent bond formed between amino group of one amino acid and carboxyl group of another by dehydration.

• Hydrogen Bond: Weak bond formed between a hydrogen atom and electronegative atom like oxygen or nitrogen.

• Phosphodiester Bond: Covalent bond linking nucleotides in DNA and RNA between phosphate and sugar moieties.

• Glycosidic Bond: Covalent bond connecting sugar molecules in carbohydrates.

• Dehydration Reaction: Chemical reaction involving elimination of water to form a new covalent bond.

• Protein: Macromolecule composed of amino acids linked via peptide bonds.

• Covalent Bond: Strong chemical bond formed by sharing electrons between atoms.

• Polypeptide: Chain of amino acids linked by peptide bonds forming protein backbone.

Lead Question - 2022 (Abroad)

Which of the following bond is formed as a result of reaction of carboxyl group of one amino acid with amino group of other amino acid with elimination of water?

1. Phosphodiester Bond

2. Hydrogen Bond

3. Glycosidic Bond

4. Peptide Bond

Explanation: When the carboxyl group of one amino acid reacts with the amino group of another amino acid, a covalent bond called a peptide bond is formed. This reaction involves elimination of a water molecule, known as a dehydration synthesis. Peptide bonds link amino acids to form proteins. Answer: Peptide Bond. Answer: 4

Q1: Which functional group in amino acids donates a hydrogen for hydrogen bonding in protein secondary structure?

1. Carboxyl Group

2. Amino Group

3. Hydroxyl Group

4. R Group

Explanation: In protein secondary structures like alpha-helix and beta-sheet, the hydrogen of the amino group (-NH) forms hydrogen bonds with the oxygen of carboxyl group (-C=O) of another amino acid, stabilizing the structure. Answer: Amino Group. Answer: 2

Q2: The bond between sugar and phosphate in DNA is called:

1. Peptide Bond

2. Phosphodiester Bond

3. Glycosidic Bond

4. Hydrogen Bond

Explanation: In DNA and RNA, nucleotides are linked via phosphodiester bonds between the 3'-OH of one sugar and 5'-phosphate of another. Peptide bonds link amino acids, glycosidic bonds link sugars, and hydrogen bonds form base pairs. Answer: Phosphodiester Bond. Answer: 2

Q3: Which bond is primarily responsible for the tertiary structure of proteins?

1. Peptide Bond

2. Disulfide Bond

3. Hydrogen Bond

4. Glycosidic Bond

Explanation: Tertiary structure of proteins is stabilized by interactions between R-groups, including disulfide bonds (covalent), hydrogen bonds, ionic bonds, and hydrophobic interactions. Peptide bonds form primary structure, glycosidic bonds are in carbohydrates. Answer: Disulfide Bond. Answer: 2

Q4: Polypeptide chains are formed by repeating:

1. Glycosidic bonds

2. Peptide bonds

3. Phosphodiester bonds

4. Hydrogen bonds

Explanation: Amino acids are linked by peptide bonds to form polypeptides, which fold into functional proteins. Glycosidic bonds link sugars, phosphodiester bonds link nucleotides, and hydrogen bonds stabilize secondary structures. Answer: Peptide Bonds. Answer: 2

Q5: Which reaction forms a peptide bond?

1. Hydrolysis

2. Dehydration synthesis

3. Oxidation

4. Reduction

Explanation: Peptide bonds are formed by dehydration synthesis, where a water molecule is eliminated between the amino group of one amino acid and the carboxyl group of another. Hydrolysis breaks the bond. Answer: Dehydration synthesis. Answer: 2

Q6: Which bond type is covalent and links amino acids?

1. Hydrogen Bond

2. Disulfide Bond

3. Peptide Bond

4. Van der Waals

Explanation: Peptide bonds are covalent bonds linking amino acids to form proteins. Hydrogen bonds are weak interactions, disulfide bonds form between cysteine residues, and Van der Waals interactions are weak non-covalent forces. Answer: Peptide Bond. Answer: 3

Q7: Assertion (A): Proteins are formed by condensation of amino acids.
Reason (R): Peptide bonds are formed with elimination of water between amino acids.

1. A is correct but R is not correct

2. A is not correct but R is correct

3. Both A and R are correct and R explains A

4. Both A and R are correct but R does not explain A

Explanation: Proteins are polypeptides formed by condensation reactions of amino acids. Peptide bonds are covalent linkages formed by elimination of water between amino and carboxyl groups. Both statements are true, and the reason explains the assertion. Answer: Both A and R are correct and R explains A. Answer: 3

Q8: Match the bond with biomolecule:

1. Peptide Bond    A. Proteins
2. Glycosidic Bond    B. Carbohydrates
3. Phosphodiester Bond    C. Nucleic Acids

1. 1-A, 2-B, 3-C

2. 1-B, 2-A, 3-C

3. 1-C, 2-B, 3-A

4. 1-A, 2-C, 3-B

Explanation: Peptide bonds link amino acids in proteins, glycosidic bonds link monosaccharides in carbohydrates, and phosphodiester bonds link nucleotides in nucleic acids. Correct matching is 1-A, 2-B, 3-C. Answer: 1

Q9: Hydrolysis of a peptide bond requires ______.

1. Water

2. ATP

3. Enzymes only

4. Heat only

Explanation: Peptide bond hydrolysis breaks the bond between amino acids by adding water, often catalyzed by protease enzymes. ATP or heat alone cannot cleave the bond efficiently. Answer: Water. Answer: 1

Q10: Select correct statements regarding peptide bonds:

1. Formed between amino and carboxyl groups

2. Involves elimination of water

3. Links amino acids to form polypeptides

4. Is a covalent bond

Explanation: Peptide bonds form covalent linkages between amino and carboxyl groups of amino acids via dehydration reaction, creating polypeptides. All four statements correctly describe peptide bonds. Answer: 1,2,3,4

Subtopic: Biological Molecules and Their Functions

Keyword Definitions:
- Glycogen: Polysaccharide storing glucose in animals.
- Globulin: Plasma protein involved in transport and immunity.
- Steroids: Lipid molecules acting as hormones.
- Thrombin: Enzyme involved in blood clotting.
- Biocatalyst: Substance that speeds up biochemical reactions, usually an enzyme.
- Antibody: Protein that recognizes and neutralizes foreign molecules.
- Hormone: Chemical messenger regulating physiological processes.
- Storage product: Molecules stored in cells for future energy use.
- Polysaccharide: Carbohydrate composed of many monosaccharide units.
- Enzyme: Protein catalyzing biochemical reactions.
- Plasma protein: Proteins in blood with structural, transport, or immune roles.

Lead Question - 2022:
Match List - I with List - II
List - I List - II
(a) Glycogen (i) Hormone
(b) Globulin (ii) Biocatalyst
(c) Steroids (iii) Antibody
(d) Thrombin (iv) Storage product
Choose the correct answer from the options given below:
(1) (a)-(iv), (b)-(ii), (c)-(i), (d)-(iii)
(2) (a)-(ii), (b)-(iv), (c)-(iii), (d)-(i)
(3) (a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)
(4) (a)-(iii), (b)-(ii), (c)-(iv), (d)-(i)

Explanation: The correct answer is (3). Glycogen is a storage product of glucose in animals. Globulin functions as an antibody in immunity. Steroids act as hormones regulating physiological processes. Thrombin is a biocatalyst enzyme responsible for blood clotting. Each molecule is accurately matched with its function.

1. Single Correct Answer:
Which molecule stores glucose in animal cells?
(a) Globulin
(b) Glycogen
(c) Steroids
(d) Thrombin
Explanation: Glycogen is a storage polysaccharide in animals, storing glucose for energy. Globulin transports substances, steroids act as hormones, and thrombin is an enzyme in clotting. Therefore, glycogen is the primary storage product of glucose in animal cells.

2. Single Correct Answer:
Which molecule functions as an antibody?
(a) Glycogen
(b) Steroids
(c) Globulin
(d) Thrombin
Explanation: Globulin includes immunoglobulins, which act as antibodies recognizing and neutralizing pathogens. Glycogen stores energy, steroids act as chemical messengers, and thrombin catalyzes blood clotting. Hence, globulin performs the primary immune defense role as antibodies.

3. Single Correct Answer:
Which molecule acts as a hormone?
(a) Glycogen
(b) Globulin
(c) Steroids
(d) Thrombin
Explanation: Steroids act as hormones regulating physiological processes, including metabolism and reproduction. Glycogen stores glucose, globulin functions as an antibody, and thrombin is a clotting enzyme. Therefore, steroids serve as chemical messengers in the body.

4. Single Correct Answer:
Which is a blood-clotting enzyme?
(a) Glycogen
(b) Thrombin
(c) Globulin
(d) Steroids
Explanation: Thrombin is a biocatalyst enzyme converting fibrinogen into fibrin during blood clotting. Glycogen stores glucose, globulin acts as antibody, and steroids act as hormones. Thrombin’s enzymatic role ensures rapid formation of a clot to prevent excessive bleeding.

5. Single Correct Answer:
Which molecule is a polysaccharide?
(a) Glycogen
(b) Globulin
(c) Thrombin
(d) Steroids
Explanation: Glycogen is a polysaccharide composed of glucose units linked together for energy storage. Globulin and thrombin are proteins, while steroids are lipids. Glycogen’s structure allows rapid mobilization of glucose when the body requires energy.

6. Single Correct Answer:
Which protein functions as a biocatalyst?
(a) Globulin
(b) Thrombin
(c) Glycogen
(d) Steroids
Explanation: Thrombin is an enzyme acting as a biocatalyst in blood coagulation. Globulin functions as an antibody, glycogen stores glucose, and steroids act as hormones. Enzymatic activity of thrombin accelerates the conversion of fibrinogen to fibrin during clot formation.

7. Assertion-Reason MCQ:
Assertion (A): Glycogen is a storage molecule.
Reason (R): It is composed of linked glucose units forming a polysaccharide.
(a) Both A and R are true, R is correct explanation of A
(b) Both A and R are true, R is not correct explanation of A
(c) A is true, R is false
(d) A is false, R is true
Explanation: Option (a) is correct. Glycogen stores glucose for energy in animals. It is a polysaccharide composed of linked glucose units. Both assertion and reason are true, and the reason directly explains why glycogen serves as an energy storage molecule.

8. Matching Type MCQ:
Match molecules with their primary functions:
List - I List - II
(a) Glycogen (i) Storage product
(b) Globulin (ii) Antibody
(c) Steroids (iii) Hormone
(d) Thrombin (iv) Biocatalyst
Options:
(1) a-i, b-ii, c-iii, d-iv
(2) a-ii, b-iv, c-i, d-iii
(3) a-iii, b-i, c-iv, d-ii
(4) a-iv, b-iii, c-ii, d-i
Explanation: Option (1) is correct. Glycogen stores energy, globulin functions as antibodies, steroids act as hormones, and thrombin is a biocatalyst. This mapping accurately aligns molecules with their biological roles.

9. Fill in the Blanks:
________ acts as a chemical messenger regulating physiological processes.
(a) Glycogen
(b) Globulin
(c) Steroids
(d) Thrombin
Explanation: Steroids act as hormones, chemical messengers controlling metabolism, growth, and reproduction. Glycogen stores glucose, globulin acts as antibody, thrombin is a blood-clotting enzyme. Hormonal activity of steroids ensures coordination of complex physiological processes across organs and tissues.

10. Choose the Correct Statements:
Identify correct statements:
1. Glycogen is a storage polysaccharide.
2. Globulin acts as an antibody.
3. Steroids function as biocatalysts.
4. Thrombin is an enzyme involved in clotting.
Options:
(a) 1, 2, 3
(b) 1, 2, 4
(c) 2, 3, 4
(d) 1, 3, 4
Explanation: Option (b) is correct. Glycogen stores glucose, globulin acts as antibody, and thrombin functions as enzyme in clotting. Steroids act as hormones, not enzymes, making statement 3 incorrect. All other statements correctly describe biomolecules and their biological roles.

Chapter: Carbohydrates
Topic: Disaccharides
Subtopic: Formation of Maltose

Keyword Definitions:

• Glucose: A simple monosaccharide sugar with formula C6H12O6, primary energy source for cells.

• Maltose: A disaccharide formed by two glucose molecules linked via a glycosidic bond.

• Dehydration Reaction: A chemical reaction where two molecules combine with loss of water (H2O).

• Glycosidic Bond: Covalent bond formed between carbohydrate molecules during disaccharide formation.

Lead Question (2022):
A dehydration reaction links two glucose molecules to produce maltose. If the formula for glucose is C6H12O6, then what is the formula for maltose:
(1) C12H24O12
(2) C12H22O11
(3) C12H24O11
(4) C12H20O10

Explanation: Two glucose molecules (C6H12O6 each) combine via a dehydration reaction, losing one H2O molecule. Thus, C6H12O6 + C6H12O6 – H2O = C12H22O11. Maltose has the formula C12H22O11. Hence, the correct answer is option (2).

1. Maltose is classified as a:
(1) Monosaccharide
(2) Disaccharide
(3) Polysaccharide
(4) Oligosaccharide

Explanation: Maltose is a disaccharide composed of two glucose units joined by an α-1,4-glycosidic bond. Monosaccharides are single sugars, polysaccharides have many units, and oligosaccharides have 3-10 sugar units. Hence, the correct answer is option (2).

2. Which type of bond joins two glucose molecules in maltose?
(1) Peptide bond
(2) Phosphodiester bond
(3) Glycosidic bond
(4) Hydrogen bond

Explanation: Two glucose molecules in maltose are linked by an α-1,4-glycosidic bond formed during dehydration reaction. Peptide bonds join amino acids, phosphodiester bonds join nucleotides, and hydrogen bonds are non-covalent interactions. Hence, the correct answer is option (3).

3. Dehydration synthesis results in:
(1) Formation of water molecule
(2) Breaking of glycosidic bond
(3) Hydrolysis of disaccharide
(4) Release of CO2

Explanation: Dehydration synthesis joins two monosaccharides with the loss of one water molecule (H2O), forming a disaccharide. It is opposite to hydrolysis, which breaks glycosidic bonds. Hence, the correct answer is option (1).

4. Which of the following disaccharides is NOT made of glucose units?
(1) Maltose
(2) Lactose
(3) Cellobiose
(4) Trehalose

Explanation: Lactose is composed of glucose and galactose, whereas maltose, cellobiose, and trehalose are glucose-glucose disaccharides. Hence, the correct answer is option (2).

5. Hydrolysis of maltose produces:
(1) Two fructose molecules
(2) Two glucose molecules
(3) Glucose and galactose
(4) Glucose and fructose

Explanation: Maltose is composed of two glucose units. Hydrolysis of maltose by maltase breaks the glycosidic bond, yielding two glucose molecules. Hence, the correct answer is option (2).

6. In maltose, the glycosidic bond is formed between:
(1) C1 of first glucose and C4 of second glucose
(2) C1 and C6 of same glucose
(3) C2 and C3 of glucose molecules
(4) C4 of first and C4 of second glucose

Explanation: In maltose, the α-1,4-glycosidic bond links C1 of the first glucose to C4 of the second glucose. This bond forms during dehydration synthesis. Hence, the correct answer is option (1).

7. Assertion (A): Maltose is a reducing sugar.
Reason (R): It has a free aldehyde group or hemiacetal functional group.
(1) Both A and R are true and R is correct explanation
(2) Both A and R are true but R is not correct explanation
(3) A is true, R is false
(4) A is false, R is true

Explanation: Maltose is a reducing sugar because the anomeric carbon of the second glucose is free and can form an aldehyde group in equilibrium. This allows it to reduce mild oxidizing agents. Hence, the correct answer is option (1).

8. Matching Type: Match disaccharides with monosaccharide components:
A. Maltose – 1. Glucose + Galactose
B. Lactose – 2. Glucose + Glucose
C. Sucrose – 3. Glucose + Fructose
(1) A–2, B–1, C–3
(2) A–1, B–2, C–3
(3) A–3, B–1, C–2
(4) A–2, B–3, C–1

Explanation: Maltose is glucose + glucose, lactose is glucose + galactose, and sucrose is glucose + fructose. Hence, the correct answer is option (1).

9. Fill in the blanks:
The disaccharide formed from two glucose molecules via a dehydration reaction is __________.

(1) Sucrose
(2) Lactose
(3) Maltose
(4) Trehalose

Explanation: Two glucose molecules combine via dehydration synthesis to form malt

Topic: DNA Structure
Subtopic: DNA Length and Base Pair Relationship

Keyword Definitions:

• DNA: Deoxyribonucleic acid, a molecule that carries genetic information in living organisms.

• Base Pair (bp): A pair of nitrogenous bases connected by hydrogen bonds in a DNA molecule, such as A–T and G–C.

• Nucleotide: Basic unit of DNA containing a sugar, phosphate group, and nitrogen base.

• Double Helix: The coiled structure of DNA with two complementary strands wound around each other.

• Genomic DNA: Total genetic material contained within an organism’s chromosomes.

Lead Question – 2022
If the length of a DNA molecule is 1.1 metres, what will be the approximate number of base pairs:
(1) 6.6×109 bp
(2) 3.3×106 bp
(3) 6.6×106 bp
(4) 3.3×109 bp

Explanation: The distance between two consecutive base pairs is 0.34 nanometres. Therefore, 1.1 m DNA equals 1.1×109 nm. Dividing by 0.34 nm per bp gives approximately 3.3×109 base pairs. Hence, the correct answer is (4).

1. In a DNA double helix, the two strands are:
(1) Parallel and identical
(2) Antiparallel and complementary
(3) Antiparallel and identical
(4) Parallel and complementary
Explanation: In DNA, one strand runs 5′ to 3′ and the other 3′ to 5′. Their base sequences are complementary (A–T, G–C). Thus, the two strands are antiparallel and complementary. Hence, the correct answer is (2).

2. The distance between two consecutive base pairs in DNA is:
(1) 0.34 nm
(2) 3.4 nm
(3) 34 nm
(4) 0.034 nm
Explanation: Each base pair in the DNA double helix is separated by a distance of 0.34 nanometres. Thus, ten base pairs together form one complete turn measuring 3.4 nm. Hence, the correct answer is (1).

3. The number of base pairs in one complete turn of B-DNA is:
(1) 5
(2) 10
(3) 15
(4) 20
Explanation: In B-form DNA, there are 10 base pairs per complete turn of the helix, and each turn measures 3.4 nm. Hence, the correct answer is (2).

4. The length of a human diploid cell DNA is approximately:
(1) 1.1 m
(2) 2.2 m
(3) 3.3 m
(4) 6.6 m
Explanation: A haploid human genome (one set of chromosomes) contains about 3.3×109 base pairs, corresponding to 1.1 m DNA. Hence, a diploid cell with two sets has approximately 2.2 m DNA. Correct answer is (2).

5. If 200 base pairs of DNA make one turn, what is its total length?
(1) 68 nm
(2) 6.8 nm
(3) 0.68 μm
(4) 0.068 μm
Explanation: Each base pair contributes 0.34 nm to the DNA length. Thus, 200 × 0.34 = 68 nm. Therefore, total length = 68 nm. Hence, the correct answer is (1).

6. Which of the following statements about DNA is correct?
(1) It contains uracil instead of thymine
(2) Its sugar component is ribose
(3) Its backbone is made of phosphate and deoxyribose sugar
(4) It is single-stranded in all organisms
Explanation: DNA is made up of deoxyribose sugar and phosphate forming its backbone, while bases (A, T, G, C) are attached. Uracil is found in RNA, not DNA. Hence, the correct answer is (3).

7. Assertion (A): DNA strands are antiparallel.
Reason (R): The hydrogen bonds form only when one strand runs 5′→3′ and the other 3′→5′.
(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: The hydrogen bonding between bases is possible only when strands are oriented oppositely (antiparallel). Thus, both A and R are true, and R correctly explains A. Hence, the correct answer is (1).

8. Match the following:
A. Hydrogen bond — (i) Adenine–Thymine
B. Phosphodiester bond — (ii) Between sugars and phosphates
C. Complementary base pairing — (iii) DNA stability
D. Double helix — (iv) Watson and Crick
Options:
(1) A-(i), B-(ii), C-(iii), D-(iv)
(2) A-(ii), B-(i), C-(iv), D-(iii)
(3) A-(iv), B-(iii), C-(ii), D-(i)
(4) A-(iii), B-(i), C-(iv), D-(ii)
Explanation: Hydrogen bonds link complementary bases (A–T, G–C), phosphodiester bonds link sugar-phosphate backbone, and the double helix structure was proposed by Watson and Crick. Hence, the correct answer is (1).

9. Fill in the blank:
Each complete turn of B-DNA measures _______ nm.
(1) 0.34
(2) 3.4
(3) 34
(4) 0.034
Explanation: In the B-form of DNA, there are 10 base pairs per turn, and the distance between adjacent base pairs is 0.34 nm. Hence, one complete turn measures 3.4 nm. Correct answer is (2).

10. Choose the correct statements:
(1) A–T pairs have three hydrogen bonds.
(2) G–C pairs have two hydrogen bonds.
(3) Base pairing follows Chargaff’s rule.
(4) A–T pairs have two hydrogen bonds.
Explanation: According to Chargaff’s rule, A pairs with T via two hydrogen bonds, and G pairs with C via three hydrogen bonds. This complementary pairing ensures structural stability of DNA. Hence, statements (3) and (4) are correct.

Topic: Lipids and Fatty Acids
Subtopic: Structure, Properties, and Biological Importance of Lipids

Keyword Definitions:

• Lipids: Organic compounds that are insoluble in water but soluble in organic solvents.

• Fatty acids: Long hydrocarbon chains with a carboxylic acid group.

• Saturated fatty acids: Fatty acids without double bonds between carbon atoms.

• Unsaturated fatty acids: Fatty acids with one or more double bonds (C=C).

• Lecithin: A phospholipid found in cell membranes, not a glycolipid.

• Monoglycerides: Formed by esterification of one fatty acid molecule with glycerol.

Lead Question (2022):
Read the following statements on lipids and find out correct set of statements.
(a) Lecithin found in the plasma membrane is a glycolipid
(b) Saturated fatty acids possess one or more C=C bonds
(c) Gingely oil has lower melting point, hence remains as oil in winter
(d) Lipids are generally insoluble in water but soluble in some organic solvents
(e) When fatty acid is esterified with glycerol, monoglycerides are formed
Choose the correct answer from the options given below:
(1) (a), (d), and (e) only
(2) (c), (d), and (e) only
(3) (a), (b), and (d) only
(4) (a), (b), and (c) only

Explanation: Lecithin is a phospholipid, not a glycolipid. Saturated fatty acids lack double bonds, while gingely oil (unsaturated) remains liquid due to low melting point. Lipids are insoluble in water but dissolve in organic solvents. Fatty acids esterify with glycerol to form monoglycerides. Hence, correct answer is (2) (c), (d), and (e) only.

1. Guessed Question:
Which of the following is a derived lipid?
(1) Waxes
(2) Steroids
(3) Triglycerides
(4) Phospholipids

Explanation: Derived lipids are obtained by hydrolysis of simple and compound lipids. Steroids, including cholesterol and hormones, belong to this group. They play crucial roles in membrane structure and signaling. Hence, the correct answer is (2) Steroids.

2. Guessed Question:
Which statement about unsaturated fatty acids is correct?
(1) They have higher melting points
(2) They are solid at room temperature
(3) They contain double bonds
(4) They are completely hydrogenated

Explanation: Unsaturated fatty acids contain one or more double bonds in their hydrocarbon chain, resulting in kinks that lower melting points. Thus, they remain liquid at room temperature, as seen in vegetable oils. Hence, the correct answer is (3) They contain double bonds.

3. Guessed Question:
Which of the following is NOT a simple lipid?
(1) Fats
(2) Oils
(3) Waxes
(4) Phospholipids

Explanation: Simple lipids include fats, oils, and waxes formed by fatty acids and alcohol. Phospholipids are compound lipids, containing phosphorus, nitrogen, and other groups. Hence, the correct answer is (4) Phospholipids.

4. Guessed Question:
Which of the following lipid functions is correct?
(1) Structural component of cell wall
(2) Long-term energy storage
(3) Genetic information storage
(4) Enzyme catalysis

Explanation: Lipids serve as long-term energy reserves, providing more energy per gram than carbohydrates. They also form cellular membranes and act as signaling molecules. Hence, the correct answer is (2) Long-term energy storage.

5. Guessed Question:
Which of the following lipids is amphipathic?
(1) Cholesterol
(2) Phospholipids
(3) Triglycerides
(4) Sterols

Explanation: Phospholipids possess hydrophilic (polar head) and hydrophobic (fatty acid tails) regions, making them amphipathic. This property allows them to form lipid bilayers in membranes. Hence, the correct answer is (2) Phospholipids.

6. Guessed Question:
Which statement about triglycerides is TRUE?
(1) They are polymers of glucose
(2) They consist of glycerol and three fatty acids
(3) They contain phosphates
(4) They are hydrophilic

Explanation: Triglycerides are formed by the esterification of glycerol with three fatty acid molecules. They are hydrophobic and serve as major energy storage molecules in animals. Hence, the correct answer is (2) They consist of glycerol and three fatty acids.

7. Assertion-Reason Question:
Assertion (A): Saturated fats are solid at room temperature.
Reason (R): They have no double bonds between carbon atoms.
(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: Saturated fats have tightly packed molecules due to absence of double bonds, resulting in higher melting points and solid form at room temperature. Hence, both A and R are true and R correctly explains A. Correct answer is (1).

8. Matching Type Question:
Match the following lipids with their functions:
A. Cholesterol — (i) Energy storage
B. Phospholipids — (ii) Membrane structure
C. Triglycerides — (iii) Hormone precursor
Options:
(1) A–iii, B–ii, C–i
(2) A–ii, B–iii, C–i
(3) A–i, B–ii, C–iii
(4) A–iii, B–i, C–ii

Explanation: Cholesterol acts as a hormone precursor, phospholipids contribute to membrane structure, and triglycerides store energy. Hence, the correct answer is (1) A–iii, B–ii, C–i.

9. Fill in the Blanks:
Lipids are composed mainly of ______ and ______.
(1) Carbon and hydrogen
(2) Oxygen and nitrogen
(3) Nitrogen and sulfur
(4) Carbon and phosphorus

Explanation: Lipids are primarily composed of carbon and hydrogen atoms with smaller amounts of oxygen. This composition makes them non-polar and insoluble in water. Hence, the correct answer is (1) Carbon and hydrogen.

10. Choose the Correct Statements:
(a) Lipids are hydrophilic compounds.
(b) Steroids are examples of derived lipids.
(c) Fats yield more energy than carbohydrates.
(d) Lecithin is a glycolipid.
(1) (a) and (d) only
(2) (b) and (c) only
(3) (a), (b), and (c) only
(4) (b), (c), and (d) only

Explanation: Lipids are hydrophobic, not hydrophilic. Steroids are derived lipids, and fats provide more energy than carbohydrates. Lecithin is a phospholipid, not a glycolipid. Hence, the correct answer is (2) (b) and (c) only.

Topic: Lipids
Subtopic: Types and Properties of Lipids

Keyword Definitions:

• Lipids: Organic molecules that are hydrophobic, include fats, oils, phospholipids, and steroids, serving as energy storage and structural components.

• Unsaturated fatty acids: Fatty acids containing one or more double bonds between carbon atoms.

• Phospholipids: Lipids containing a phosphate group, forming cell membrane components like lecithin.

• Glycerol: Trihydroxy alcohol forming the backbone of triglycerides and phospholipids.

• Palmitic acid: A saturated fatty acid with 16 carbon atoms including carboxyl carbon.

• Arachidonic acid: A polyunsaturated fatty acid with 20 carbon atoms.

Lead Question - 2021

Following are the statements with reference to 'lipids'.
(a) Lipids having only single bonds are called unsaturated fatty acids.
(b) Lecithin is a phospholipid
(c) Trihydroxy propane is glycerol.
(d) Palmitic acid has 20 carbon atoms including carboxyl carbon
(e) Arachidonic acid has 16 carbon atoms
Choose the correct answer from the options given below

(1) (c) and (d) only
(2) (b) and (c) only
(3) (b) and (e) only
(4) (a) and (b) only

Explanation: Statement (a) is incorrect; lipids with only single bonds are saturated fatty acids. Lecithin is a phospholipid (b), and trihydroxy propane is glycerol (c). Palmitic acid has 16 carbons, not 20, and arachidonic acid has 20 carbons, not 16. Correct answer is option (2) (b) and (c) only.

1. Which fatty acid has one double bond?
(1) Palmitic acid
(2) Oleic acid
(3) Stearic acid
(4) Lauric acid
Explanation: Oleic acid is a monounsaturated fatty acid with one double bond, while palmitic, stearic, and lauric acids are saturated. Monounsaturated fatty acids influence membrane fluidity and health benefits. Correct answer is option (2) Oleic acid.

2. Which component forms the hydrophilic head of phospholipids?
(1) Fatty acid
(2) Glycerol
(3) Phosphate group
(4) Triglyceride
Explanation: The phosphate group forms the polar hydrophilic head of phospholipids, while fatty acids form hydrophobic tails. Glycerol acts as the backbone connecting the head and tails. Correct answer is option (3) Phosphate group.

3. Which lipid is a primary energy storage molecule?
(1) Phospholipid
(2) Triglyceride
(3) Steroid
(4) Lecithin
Explanation: Triglycerides store energy efficiently in adipose tissue, composed of glycerol and three fatty acids. Phospholipids are structural, steroids regulate metabolism, and lecithin is a phospholipid. Correct answer is option (2) Triglyceride.

4. Which lipid forms the bilayer of cell membranes?
(1) Steroids
(2) Triglycerides
(3) Phospholipids
(4) Wax
Explanation: Phospholipids arrange into bilayers forming the fundamental structure of cell membranes, with hydrophilic heads outside and hydrophobic tails inside. Steroids modulate fluidity, triglycerides store energy, waxes provide protection. Correct answer is option (3) Phospholipids.

5. Which lipid contains four fused rings?
(1) Triglyceride
(2) Phospholipid
(3) Steroid
(4) Glycolipid
Explanation: Steroids have a structure of four fused hydrocarbon rings, examples include cholesterol and hormones. Triglycerides are glycerol + fatty acids, phospholipids form membranes, glycolipids are membrane lipids with sugar. Correct answer is option (3) Steroid.

6. Which fatty acid is polyunsaturated?
(1) Stearic acid
(2) Palmitic acid
(3) Arachidonic acid
(4) Lauric acid
Explanation: Arachidonic acid is a polyunsaturated fatty acid with four double bonds, important in eicosanoid synthesis. Stearic, palmitic, and lauric acids are saturated fatty acids. Correct answer is option (3) Arachidonic acid.

7. Assertion-Reason Question:
Assertion (A): Glycerol is the backbone of triglycerides.
Reason (R): Triglycerides consist of three fatty acids esterified to a trihydroxy alcohol.
(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: Glycerol, a trihydroxy alcohol, serves as the backbone for triglycerides, linking three fatty acids via ester bonds. This makes the reason correct explanation of the assertion. Correct answer is option (1).

8. Matching Type Question:
Match lipid types with examples:
(a) Saturated fatty acid - 1. Oleic acid
(b) Polyunsaturated fatty acid - 2. Arachidonic acid
(c) Phospholipid - 3. Lecithin
(d) Steroid - 4. Cholesterol
(1) a-1, b-2, c-3, d-4
(2) a-2, b-1, c-4, d-3
(3) a-4, b-3, c-2, d-1
(4) a-3, b-4, c-1, d-2
Explanation: Saturated fatty acid example: palmitic acid (a-1), polyunsaturated: arachidonic acid (b-2), phospholipid: lecithin (c-3), steroid: cholesterol (d-4). Correct answer is option (1).

9. Fill in the Blanks:
______ is a trihydroxy alcohol forming the backbone of triglycerides.
(1) Glycerol
(2) Palmitic acid
(3) Oleic acid
(4) Lecithin
Explanation: Glycerol, a trihydroxy alcohol, forms the backbone of triglycerides by esterifying three fatty acids. Palmitic and oleic acids are fatty acids, lecithin is a phospholipid. Correct answer is option (1) Glycerol.

10. Choose the correct statements:
(a) Saturated fatty acids have single bonds
(b) Unsaturated fatty acids have one or more double bonds
(c) Phospholipids form cell membranes
(d) Arachidonic acid has 16 carbon atoms
(1) a, b, c
(2) a, c, d
(3) b, c, d
(4) a, b, d
Explanation: Saturated fatty acids have single bonds (a), unsaturated fatty acids have one or more double bonds (b), and phospholipids form cell membranes (c). Arachidonic acid has 20 carbons, not 16 (d incorrect). Correct answer is option (1) a, b, c.

Topic: DNA Structure

Subtopic: Base Pairing

• DNA: Deoxyribonucleic acid, a molecule carrying genetic instructions.

• Adenine (A): A purine base in DNA that pairs with thymine.

• Thymine (T): A pyrimidine base in DNA that pairs with adenine.

• Guanine (G): A purine base in DNA that pairs with cytosine.

• Cytosine (C): A pyrimidine base in DNA that pairs with guanine.

• Base pairing: Complementary pairing of DNA bases: A-T and G-C.

• Purine: Double-ring nitrogenous base (A and G) in DNA.

• Pyrimidine: Single-ring nitrogenous base (T and C) in DNA.

• Chargaff's rule: In DNA, %A=%T and %G=%C.

• Genetic code: Sequence of nucleotides that determines traits.

• Double helix: DNA structure with two complementary strands.

Lead Question - 2021

If Adenine makes 30% of the DNA molecule, what will be the percentage of Thymine, Guanine and Cytosine in it?

(1) T: 20 ; G: 20 ; C: 30
(2) T: 30 ; G: 20 ; C: 20
(3) T: 20 ; G: 25 ; C: 25
(4) T: 20 ; G: 30 ; C: 20

Explanation: According to Chargaff's rule, %A = %T and %G = %C. If Adenine is 30%, Thymine is also 30%. Total percentage of A+T = 60%, so remaining 40% is shared equally by G and C, giving G=20% and C=20%. Answer: T:30; G:20; C:20.

1. Single Correct Answer MCQ: Which base pairs with Guanine in DNA?
Options:
A. Adenine
B. Thymine
C. Cytosine
D. Uracil

Explanation: In DNA, Guanine pairs with Cytosine via three hydrogen bonds. Adenine pairs with Thymine. Uracil is found in RNA, not DNA. Answer: Cytosine.

2. Single Correct Answer MCQ: If Cytosine is 15%, what is the percentage of Guanine?
Options:
A. 15
B. 30
C. 35
D. 20

Explanation: Chargaff's rule states %C=%G. If Cytosine is 15%, Guanine is also 15%. Answer: 15.

3. Single Correct Answer MCQ: Total percentage of purines in DNA if A=30% and G=20% is:
Options:
A. 50%
B. 40%
C. 60%
D. 30%

Explanation: Purines are Adenine and Guanine. A=30%, G=20%, total purines = 30+20 = 50%. Answer: 50%.

4. Single Correct Answer MCQ: What is the percentage of Pyrimidines if A=30% and G=20%?
Options:
A. 30%
B. 50%
C. 40%
D. 20%

Explanation: Pyrimidines are Thymine and Cytosine. %T=%A=30%, %C=%G=20%, total = 30+20 = 50%. Answer: 50%.

5. Single Correct Answer MCQ: Which rule determines base pairing in DNA?
Options:
A. Mendel’s law
B. Chargaff’s rule
C. Hardy-Weinberg principle
D. Law of segregation

Explanation: Chargaff’s rule specifies complementary base pairing: %A=%T, %G=%C in DNA. Other laws are unrelated to base pairing. Answer: Chargaff’s rule.

6. Single Correct Answer MCQ: Which base is not a pyrimidine?
Options:
A. Cytosine
B. Thymine
C. Adenine
D. Uracil

Explanation: Pyrimidines include Cytosine, Thymine, and Uracil. Adenine is a purine. Answer: Adenine.

7. Assertion-Reason MCQ:
Assertion (A): DNA has equal amounts of A and T.
Reason (R): Purine always pairs with a pyrimidine.
Options:
A. Both A and R true, R correct explanation
B. Both A and R true, R not correct explanation
C. A true, R false
D. A false, R true

Explanation: In DNA, A=T and G=C. Purines (A,G) pair with pyrimidines (T,C). Both assertion and reason are true, and R explains A correctly. Answer: Both A and R true, R correct explanation.

8. Matching Type MCQ:
List I: 1. Purines 2. Pyrimidines 3. Base pairing 4. Double helix
List II: A. A-T, G-C B. A,G C. C,T D. Two strands coiled
Options:
A. 1-B, 2-C, 3-A, 4-D
B. 1-C, 2-B, 3-A, 4-D
C. 1-B, 2-C, 3-D, 4-A
D. 1-A, 2-C, 3-B, 4-D

Explanation: Purines are A and G, Pyrimidines are C and T, Base pairing: A-T, G-C, Double helix: two coiled strands. Answer: 1-B, 2-C, 3-A, 4-D.

9. Fill in the Blank MCQ: The percentage of Thymine equals ______.
Options:
A. Adenine
B. Guanine
C. Cytosine
D. Total purines

Subtopic: Bonds in Biomolecules

Keyword Definitions:

• Peptide bond: Covalent bond formed between two amino acids in proteins.

• Glycosidic bond: Covalent bond that joins monosaccharides to form polysaccharides.

• Phosphodiester bond: Linkage connecting nucleotides in nucleic acids.

• Unsaturated fatty acid: Fatty acid containing one or more C=C double bonds.

• Macromolecules: Large molecules essential for life including proteins, nucleic acids, carbohydrates, and lipids.

Lead Question - 2021
Match List - I with List - II.
List - I        List - II
(a) Protein          (i) C=C double bonds
(b) Unsaturated fatty acid    (ii) Phosphodiester bonds
(c) Nucleic acid       (iii) Glycosidic bonds
(d) Polysaccharide   (iv) Peptide bonds

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

Explanation: Proteins are linked by peptide bonds, unsaturated fatty acids by C=C double bonds, nucleic acids by phosphodiester bonds, and polysaccharides by glycosidic bonds. Thus, the correct matching is (a)–(iv), (b)–(i), (c)–(ii), (d)–(iii). The correct answer is (4).

1. Which bond is responsible for linking amino acids in a polypeptide chain?
(1) Hydrogen bond
(2) Glycosidic bond
(3) Peptide bond
(4) Phosphodiester bond

Explanation: In proteins, amino acids are joined by peptide bonds formed between the amino group of one amino acid and the carboxyl group of another. This bond is covalent and provides primary structure stability. Thus, the correct answer is (3) Peptide bond.

2. Which bond connects monosaccharides to form polysaccharides like starch?
(1) Hydrogen bond
(2) Peptide bond
(3) Glycosidic bond
(4) Phosphodiester bond

Explanation: Polysaccharides such as starch, glycogen, and cellulose are formed by glycosidic bonds between monosaccharide units. These bonds are covalent and help in energy storage and structural roles. Thus, the correct answer is (3) Glycosidic bond.

3. Assertion (A): Phosphodiester bonds link nucleotides in DNA.
Reason (R): They connect phosphate of one nucleotide to sugar of another.
(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: Phosphodiester bonds form between the phosphate group of one nucleotide and the hydroxyl group of the sugar in another nucleotide, maintaining DNA and RNA backbone. Both assertion and reason are true and R explains A. Thus, the correct answer is (1).

4. Match the following molecules with their bonds:
A. Proteins
B. Polysaccharides
C. Nucleic acids
D. Lipids

(1) A–Peptide, B–Glycosidic, C–Phosphodiester, D–C=C double bond
(2) A–Glycosidic, B–Peptide, C–Phosphodiester, D–Hydrogen
(3) A–Phosphodiester, B–Peptide, C–Glycosidic, D–Hydrogen
(4) A–Hydrogen, B–Peptide, C–C=C double bond, D–Glycosidic

Explanation: Proteins are held by peptide bonds, polysaccharides by glycosidic bonds, nucleic acids by phosphodiester bonds, and lipids by C=C double bonds if unsaturated. Thus, the correct answer is (1).

5. Fill in the blank:
__________ bonds link nucleotides in nucleic acids.
(1) Glycosidic
(2) Peptide
(3) Phosphodiester
(4) Hydrogen

Explanation: In DNA and RNA, nucleotides are joined by phosphodiester bonds, which form the sugar-phosphate backbone essential for genetic material stability. Thus, the correct answer is (3) Phosphodiester.

6. Which type of bond is present in unsaturated fatty acids?
(1) Peptide bond
(2) Glycosidic bond
(3) Hydrogen bond
(4) C=C double bond

Explanation: Unsaturated fatty acids contain one or more carbon–carbon double bonds (C=C) in their hydrocarbon chains. These bonds influence fluidity and properties of cell membranes. Thus, the correct answer is (4) C=C double bond.

7. Which of the following correctly pairs the biomolecule with its primary bond?
(1) Protein – Glycosidic
(2) Nucleic acid – Phosphodiester
(3) Polysaccharide – Peptide
(4) Lipid – Peptide

Explanation: Nucleic acids such as DNA and RNA have nucleotides linked by phosphodiester bonds in their backbone. Proteins, polysaccharides, and lipids have different bonding types. Thus, the correct answer is (2) Nucleic acid – Phosphodiester.

8. Choose the correct statements about biomolecular bonds:
(1) Proteins are formed by peptide bonds.
(2) Polysaccharides are formed by glycosidic bonds.
(3) Nucleic acids are formed by phosphodiester bonds.
(4) Lipids contain C=C double bonds if unsaturated.
(1) 1 and 2 only
(2) 2 and 4 only
(3) 1, 2 and 3 only
(4) 1, 2, 3 and 4

Explanation: All listed statements are correct. Proteins – peptide bonds, polysaccharides – glycosidic bonds, nucleic acids – phosphodiester bonds, lipids – C=C double bonds if unsaturated. Thus, the correct answer is (4) 1, 2, 3 and 4.

9. In proteins, peptide bonds are formed between:
(1) Carboxyl group of one amino acid and amino group of another
(2) Hydroxyl groups of two amino acids
(3) Phosphate and hydroxyl groups
(4) Sugar and nitrogenous base

Explanation: Peptide bonds form between the carboxyl group of one amino acid and the amino group of another, releasing a molecule of water in a condensation reaction. Thus, the correct answer is (1).

10. Which bond is most stable and resistant to degradation?
(1) Glycosidic bond
(2) Peptide bond
(3) Phosphodiester bond
(4) C=C double bond

Explanation: Among the listed, phosphodiester bonds in DNA are highly stable, enabling long-term storage of genetic information. This stability is essential for heredity. Thus, the correct answer is (3) Phosphodiester bond.

Topic: DNA Structure and Analysis
Subtopic: Gel Electrophoresis and DNA Visualization

Keyword Definitions:

• DNA: Deoxyribonucleic acid, the molecule carrying genetic instructions.

• Ethidium Bromide: A fluorescent dye that intercalates between DNA bases for visualization under UV light.

• Gel Electrophoresis: A technique to separate DNA fragments by size using an electric field in agarose gel.

• UV Radiation: Ultraviolet light used to visualize DNA bound to ethidium bromide.

• DNA Bands: Distinct visual representations of DNA fragments on a gel.

• Intercalation: The insertion of molecules like ethidium bromide between DNA base pairs.

• Agarose Gel: A porous medium for electrophoretic separation of nucleic acids.

• Fluorescence: Emission of visible light by a substance after absorbing light.

Lead Question - 2021

DNA strands on a gel stained with ethidium bromide when viewed under UV radiation, appear as:
(1) Bright orange bands
(2) Dark red bands
(3) Bright blue bands
(4) Yellow bands

Explanation: Correct answer is (1) Bright orange bands. Ethidium bromide intercalates into DNA and fluoresces bright orange under UV light, allowing visualization of DNA fragments. Other colors do not accurately represent ethidium bromide-DNA fluorescence, which is a standard technique in molecular biology labs for gel electrophoresis.

Guessed Questions:

1) Single Correct Answer: Which dye intercalates between DNA bases for visualization?
(1) Methylene Blue
(2) Ethidium Bromide
(3) Coomassie Blue
(4) Crystal Violet

Explanation: Correct answer is (2) Ethidium Bromide. It binds between DNA base pairs and fluoresces under UV light, enabling visualization of DNA in agarose gels.

2) Single Correct Answer: UV light is used in gel electrophoresis to:
(1) Separate DNA fragments
(2) Visualize stained DNA
(3) Denature RNA
(4) Break proteins

Explanation: Correct answer is (2) Visualize stained DNA. UV light excites ethidium bromide bound to DNA, causing fluorescence, which allows observation of DNA bands.

3) Single Correct Answer: In agarose gel electrophoresis, DNA moves because of:
(1) Diffusion
(2) Electric field
(3) Gravity
(4) Centrifugal force

Explanation: Correct answer is (2) Electric field. DNA is negatively charged due to its phosphate backbone and migrates towards the positive electrode through the porous agarose matrix.

4) Single Correct Answer: DNA bands on gel represent:
(1) Protein fragments
(2) DNA fragment sizes
(3) RNA sequences
(4) Gel density

Explanation: Correct answer is (2) DNA fragment sizes. Each band corresponds to DNA fragments of a specific length, separated during electrophoresis.

5) Single Correct Answer: Fluorescence of DNA stained with ethidium bromide is due to:
(1) UV absorption and emission
(2) Heat emission
(3) Chemical reaction
(4) Light scattering

Explanation: Correct answer is (1) UV absorption and emission. Ethidium bromide absorbs UV light and emits visible orange fluorescence, enabling DNA visualization in gels.

6) Assertion-Reason:
A: DNA fluoresces bright orange under UV when stained with ethidium bromide.
R: Ethidium bromide intercalates between DNA bases and emits visible light.
(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: Correct answer is (1). The fluorescence occurs because ethidium bromide intercalates DNA and emits orange light upon UV excitation, directly explaining the observed bright orange bands.

7) Matching Type: Match the dye with its characteristic:
List-I List-II
(a) Ethidium Bromide    (i) DNA intercalating, fluoresces orange
(b) Methylene Blue    (ii) Stains DNA blue, non-fluorescent
(c) Coomassie Blue    (iii) Stains proteins
(d) Crystal Violet    (iv) Stains bacterial cells

Explanation: Correct answer: (a) i, (b) ii, (c) iii, (d) iv. Each dye has a specific binding property and visualization method, commonly used in molecular biology.

8) Single Correct Answer: Ethidium bromide is avoided in some labs due to:
(1) High cost
(2) Toxicity and mutagenicity
(3) Poor staining
(4) Low fluorescence

Explanation: Correct answer is (2) Toxicity and mutagenicity. Ethidium bromide can intercalate into genomic DNA and is a potential mutagen, so safe handling is required.

9) Fill in the blank: DNA stained with ethidium bromide fluoresces ______ under UV light.
(1) Blue
(2) Bright orange
(3) Green
(4) Red

Explanation: Correct answer is (2) Bright orange. Ethidium bromide intercalates DNA and emits bright orange fluorescence under UV light, enabling band detection in gels.

10) Choose the correct statements:
(a) Ethidium bromide binds between DNA bases.
(b) DNA appears bright orange under UV after staining.
(c) Ethidium bromide stains proteins primarily.
(d) DNA migration is towards positive electrode.
Options:
(1) a, b, d
(2) a, c, d
(3) b, c, d
(4) a, b, c

Explanation: Correct answer is (1). Statements a, b, and d are correct. Statement c is incorrect; ethidium bromide primarily stains DNA, not proteins.

Subtopic: Primary vs Secondary Metabolites

Keyword Definitions:

• Primary metabolites: Compounds like amino acids, glucose essential for growth and metabolism.

• Secondary metabolites: Non-essential compounds like alkaloids, terpenoids, phenolics with ecological functions.

• Alkaloids: Nitrogen-containing compounds such as morphine and codeine with medicinal properties.

• Terpenoids: Compounds like rubber and essential oils derived from isoprene units.

• Phenolics: Compounds like curcumin with antioxidant properties.

• Medicinal metabolites: Compounds such as vinblastine with pharmaceutical use.

• Gums: Polysaccharides secreted by plants, used in industrial and pharmaceutical processes.

Lead Question - 2021

Which of the following are not secondary metabolites in plants?
(1) Amino acids, glucose
(2) Vinblastin, curcumin
(3) Rubber, gums
(4) Morphine, codeine

Explanation: The correct answer is (1) Amino acids, glucose. These are primary metabolites essential for plant survival and cellular metabolism. Secondary metabolites such as morphine, vinblastine, and curcumin are not directly required for growth but play protective, ecological, or commercial roles. Thus, amino acids and glucose belong to primary, not secondary, metabolites.

Guessed Questions:

1) Which of the following is a secondary metabolite?
(1) Glucose
(2) Amino acid
(3) Morphine
(4) ATP

Explanation: The correct answer is (3) Morphine. It is an alkaloid and secondary metabolite used medicinally. Primary metabolites like glucose, amino acids, and ATP are essential for growth, whereas secondary metabolites like morphine function in defense and ecological interactions without being vital for plant survival.

2) Curcumin, found in turmeric, is chemically classified as:
(1) Alkaloid
(2) Terpenoid
(3) Phenolic compound
(4) Polysaccharide

Explanation: The correct answer is (3) Phenolic compound. Curcumin is a secondary metabolite with antioxidant and medicinal properties. It is not an alkaloid or terpenoid. Instead, it belongs to phenolics derived from plant biosynthetic pathways and is widely used in traditional medicine and food industries.

3) Rubber produced by plants belongs to:
(1) Alkaloids
(2) Terpenoids
(3) Phenolics
(4) Glycosides

Explanation: The correct answer is (2) Terpenoids. Rubber is a polymer of isoprene units and classified under terpenoids. These secondary metabolites protect plants and have vast industrial applications. Unlike alkaloids and phenolics, terpenoids like rubber contribute to defense and elasticity in plants.

4) Which of the following is an example of an alkaloid?
(1) Starch
(2) Morphine
(3) Cellulose
(4) Pectin

Explanation: The correct answer is (2) Morphine. Alkaloids are nitrogen-containing secondary metabolites. Morphine acts as a potent analgesic derived from the opium poppy. Compounds like starch, cellulose, and pectin are primary metabolites involved in structural and energy storage functions.

5) Gums secreted by plants are classified as:
(1) Proteins
(2) Secondary metabolites
(3) Lipids
(4) Enzymes

Explanation: The correct answer is (2) Secondary metabolites. Plant gums are polysaccharides secreted in response to injury or stress. Though not vital for basic metabolism, they provide ecological and industrial benefits. They differ from proteins, lipids, or enzymes in structure and function.

6) Which of the following is a primary metabolite?
(1) Glucose
(2) Curcumin
(3) Morphine
(4) Rubber

Explanation: The correct answer is (1) Glucose. It is a primary metabolite directly involved in cellular respiration and energy production. Secondary metabolites like curcumin, morphine, and rubber have ecological, protective, or commercial roles rather than being essential for basic metabolism and survival.

7) Assertion (A): Secondary metabolites are not directly involved in plant growth.
Reason (R): They play important roles in defense and ecological interactions.
(1) Both A and R are true, R explains A
(2) Both A and R are true, R does not explain A
(3) A is true, R is false
(4) A is false, R is true

Explanation: The correct answer is (1) Both A and R are true, R explains A. Secondary metabolites like alkaloids and phenolics are non-essential for growth but important for plant protection, competition, and signaling. Thus, their ecological roles explain why they are not directly involved in growth.

8) Match the following plant metabolites with their examples:
A. Alkaloid - (i) Morphine
B. Terpenoid - (ii) Rubber
C. Phenolic - (iii) Curcumin
D. Glycoside - (iv) Digitoxin
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-i, B-iv, C-ii, D-iii

Explanation: The correct answer is (1) A-i, B-ii, C-iii, D-iv. Alkaloids like morphine, terpenoids like rubber, phenolics like curcumin, and glycosides like digitoxin represent major secondary metabolite classes with distinct functions ranging from medicinal to ecological defense.

9) Fill in the blank: ________ is an anticancer alkaloid obtained from Catharanthus roseus.
(1) Morphine
(2) Vinblastine
(3) Curcumin
(4) Rubber

Explanation: The correct answer is (2) Vinblastine. It is a secondary metabolite alkaloid used as a chemotherapeutic drug derived from the Madagascar periwinkle. Unlike morphine or curcumin, vinblastine specifically inhibits cell division and is used in treating cancers like Hodgkin’s lymphoma and leukemia.

10) Choose the correct statements:
A. Primary metabolites include glucose and amino acids.
B. Secondary metabolites are essential for growth.
C. Morphine and curcumin are secondary metabolites.
D. Rubber is a terpenoid.
Options:
(1) A and B
(2) B and C
(3) A, C and D
(4) A and D

Explanation: The correct answer is (3) A, C and D. Primary metabolites like glucose and amino acids are essential. Secondary metabolites like morphine and curcumin play ecological roles. Rubber, a terpenoid, is also a secondary metabolite. Statement B is incorrect because secondary metabolites are not essential for growth.

Topic: DNA Replication
Subtopic: Replication Rate in Prokaryotes

Keyword Definitions:

• E. coli: A common bacterium used as a model organism in molecular biology studies.

• Base pairs: Paired nucleotides in DNA (A-T, G-C) forming the double helix.

• Replication: Process of copying DNA to produce two identical DNA molecules.

• Polymerization: Formation of a DNA strand by linking nucleotides via DNA polymerase.

• Replication rate: Speed at which DNA polymerase adds nucleotides per second.

• Prokaryotes: Organisms without a nucleus; DNA replication occurs in cytoplasm.

• Double helix: Structure of DNA formed by two complementary strands.

• DNA polymerase: Enzyme catalyzing addition of nucleotides during DNA replication.

Lead Question - 2020 (COVID Reexam)

E.coli has only 4.6 × 106 base pairs and completes the process of replication within 18 minutes; then the average rate of polymerization is approximate-

1. 2000 base pairs/second
2. 3000 base pairs/second
3. 4000 base pairs/second
4. 1000 base pairs/second

Explanation: E. coli has 4.6 × 106 base pairs. Replication time is 18 minutes = 1080 seconds. Average rate = total base pairs / time = 4.6 × 106 / 1080 ≈ 4259 ≈ 4000 base pairs/second. Correct answer: Option 3.

1. Single Correct Answer MCQ:

Which enzyme is responsible for adding nucleotides during replication?
1. DNA ligase
2. DNA polymerase
3. Helicase
4. Topoisomerase

Explanation: DNA polymerase catalyzes the addition of nucleotides to the growing DNA strand during replication, ensuring accurate synthesis. Helicase unwinds DNA, ligase joins fragments, and topoisomerase relieves supercoiling. Correct answer: Option 2.

2. Single Correct Answer MCQ:

The replication of E. coli DNA is completed in approximately:
1. 18 seconds
2. 18 minutes
3. 18 hours
4. 180 minutes

Explanation: E. coli completes DNA replication in 18 minutes, demonstrating rapid polymerization in prokaryotes. This short time is due to circular DNA and multiple replication forks. Answer: Option 2.

3. Single Correct Answer MCQ:

What is the total number of base pairs in E. coli genome?
1. 4.6 × 103
2. 4.6 × 106
3. 4.6 × 109
4. 46

Explanation: The E. coli genome contains approximately 4.6 × 106 base pairs forming a single circular DNA molecule. This small genome allows rapid replication. Correct answer: Option 2.

4. Single Correct Answer MCQ:

The time taken to replicate 1 base pair at the average rate is approximately:
1. 0.25 milliseconds
2. 0.25 seconds
3. 2.5 microseconds
4. 1 second

Explanation: At 4000 base pairs/second, time per base pair = 1/4000 sec = 0.00025 sec = 0.25 milliseconds. This shows the high efficiency of E. coli replication machinery. Correct answer: Option 1.

5. Single Correct Answer MCQ:

Which structure allows faster replication in prokaryotes?
1. Linear DNA
2. Circular DNA
3. Mitochondrial DNA
4. Plasmid only

Explanation: Circular DNA in prokaryotes like E. coli allows bidirectional replication from a single origin, leading to faster replication compared to linear DNA. Plasmids replicate independently but are smaller. Answer: Option 2.

6. Single Correct Answer MCQ:

What is the main reason E. coli replicates DNA rapidly?
1. Multiple chromosomes
2. Multiple replication origins
3. Single circular chromosome
4. Lack of DNA polymerase

Explanation: E. coli has a single circular chromosome with a single origin of replication, but replication is bidirectional, allowing rapid completion in 18 minutes. This efficiency supports fast bacterial growth. Correct answer: Option 3.

7. Assertion-Reason MCQ:

Assertion (A): E. coli completes replication in 18 minutes.
Reason (R): Its genome is small and circular, allowing fast bidirectional replication.
1. Both A and R true, R correct explanation
2. Both A and R true, R not correct explanation
3. A true, R false
4. A false, R true

Explanation: E. coli replicates its 4.6 × 106 base pair circular genome in 18 minutes due to bidirectional replication from a single origin. Both assertion and reason are correct, and reason explains assertion accurately. Answer: Option 1.

8. Matching Type MCQ:

Column I    Column II
(a) DNA polymerase    (i) Unwinds DNA
(b) Helicase    (ii) Adds nucleotides
(c) Ligase    (iii) Joins Okazaki fragments
(d) Topoisomerase    (iv) Relieves supercoiling

1. (a)-(ii), (b)-(i), (c)-(iii), (d)-(iv)
2. (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
3. (a)-(iii), (b)-(ii), (c)-(i), (d)-(iv)
4. (a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)

Explanation: DNA polymerase adds nucleotides, helicase unwinds DNA, ligase joins Okazaki fragments, and topoisomerase relieves supercoiling. Correct match: (a)-(ii), (b)-(i), (c)-(iii), (d)-(iv). Answer: Option 1.

9. Fill in the blanks:

The bidirectional replication in E. coli begins at a single ______ of replication.
1. Origin
2. Terminus
3. Fork
4. Centromere

Explanation: E. coli DNA replication begins at a single origin of replication, proceeding bidirectionally around the circular chromosome until termination. This strategy allows rapid genome duplication. Answer: Option 1.

10. Choose the correct statements MCQ:

Select the correct statements about E. coli DNA replication:
(a) Replication is bidirectional
(b) Rate ≈ 4000 base pairs

Copic: DNA Structure and Function
Subtopic: Polynucleotide Chain and Nitrogenous Bases

Keyword Definitions:

• Polynucleotide chain: A polymer of nucleotides linked by phosphodiester bonds forming DNA or RNA strands.

• Nitrogenous base: Organic molecules (A, T, G, C) attached to the sugar in nucleotides.

• Pentose sugar: Five-carbon sugar in nucleotides; deoxyribose in DNA, ribose in RNA.

• 1'C of sugar: Carbon atom in sugar where nitrogenous base attaches.

• 3'C and 5'C: Carbon atoms in sugar forming phosphodiester linkages between nucleotides.

• Phosphodiester bond: Covalent bond linking the 3'C of one sugar to 5'C of another.

• DNA strand: Sequence of nucleotides forming genetic material.

• OH group: Hydroxyl group on sugar that forms bond with phosphate or base.

Lead Question - 2020 (COVID Reexam)

In the polynucleotide chain of DNA, a nitrogenous base is linked to the –OH of:

1. 2'C pentose sugar
2. 3'C pentose sugar
3. 5'C pentose sugar
4. 1'C pentose sugar

Explanation: In DNA, each nitrogenous base (A, T, G, C) is covalently attached to the 1' carbon of the deoxyribose sugar via a β-glycosidic bond. This linkage forms the nucleoside, which combines with phosphate groups to create the polynucleotide chain. Correct answer: Option 4.

1. Single Correct Answer MCQ:

Which carbon of sugar forms the phosphodiester bond with another nucleotide?
1. 1'C
2. 2'C
3. 3'C
4. 5'C

Explanation: Phosphodiester bonds connect the 3' hydroxyl group of one sugar to the 5' phosphate of the next nucleotide, forming the backbone of DNA. The 1'C attaches to the base. Answer: Option 3.

2. Single Correct Answer MCQ:

Which sugar is present in DNA nucleotides?
1. Ribose
2. Deoxyribose
3. Glucose
4. Fructose

Explanation: DNA contains deoxyribose sugar, lacking one oxygen at the 2' carbon compared to ribose in RNA. Glucose and fructose are monosaccharides but not part of nucleotides. Correct answer: Option 2.

3. Single Correct Answer MCQ:

Which base is complementary to adenine in DNA?
1. Guanine
2. Cytosine
3. Thymine
4. Uracil

Explanation: In DNA, adenine forms two hydrogen bonds with thymine, maintaining base pairing specificity. Cytosine pairs with guanine, and uracil is in RNA. Answer: Option 3.

4. Single Correct Answer MCQ:

A nucleotide consists of:
1. Sugar only
2. Base and phosphate only
3. Sugar and base only
4. Sugar, base, and phosphate

Explanation: A nucleotide is composed of a pentose sugar, a nitrogenous base, and a phosphate group. Together, nucleotides polymerize to form DNA or RNA chains. Answer: Option 4.

5. Single Correct Answer MCQ:

Which group on sugar links with phosphate in DNA backbone?
1. 1'OH
2. 2'OH
3. 3'OH
4. 5'OH

Explanation: The 3' hydroxyl of sugar forms phosphodiester bonds with 5' phosphate of the next nucleotide, creating DNA's sugar-phosphate backbone. The 1' carbon links to the nitrogenous base. Answer: Option 3.

6. Single Correct Answer MCQ:

In DNA, thymine is attached to which carbon of sugar?
1. 1'C
2. 2'C
3. 3'C
4. 5'C

Explanation: Nitrogenous bases in DNA, including thymine, attach covalently to the 1' carbon of deoxyribose sugar, forming a nucleoside. This allows polymerization through phosphodiester bonds on 3' and 5' carbons. Answer: Option 1.

7. Assertion-Reason MCQ:

Assertion (A): Nitrogenous base is linked to 1' carbon of sugar.
Reason (R): The base forms a glycosidic bond with sugar in nucleotides.
1. Both A and R true, R correct explanation
2. Both A and R true, R not correct explanation
3. A true, R false
4. A false, R true

Explanation: The nitrogenous base attaches to the 1' carbon of the sugar via a β-glycosidic bond in nucleotides. Both assertion and reason are correct, and the reason accurately explains the assertion. Answer: Option 1.

8. Matching Type MCQ:

Column I    Column II
(a) 1' carbon    (i) Base attachment
(b) 3' carbon    (ii) Phosphodiester bond
(c) 5' carbon    (iii) Terminal phosphate
(d) Nitrogenous base    (iv) Purine or pyrimidine

1. (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
2. (a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)
3. (a)-(ii), (b)-(iii), (c)-(i), (d)-(iv)
4. (a)-(i), (b)-(iii), (c)-(ii), (d)-(iv)

Explanation: The 1' carbon attaches to the base, 3' carbon forms phosphodiester bonds, 5' carbon carries terminal phosphate, and nitrogenous base is purine or pyrimidine. Correct match: (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv). Answer: Option 1.

9. Fill in the blanks:

In DNA, a nitrogenous base is covalently attached to the ______ carbon of deoxyribose sugar.
1. 1'
2. 2'
3. 3'
4. 5'

Explanation: The nitrogenous base in DNA is attached to the 1' carbon of deoxyribose sugar via a β-glycosidic bond forming a nucleoside.

Subtopic: Discovery of Nucleic Acids

Keyword Definitions:

• Nuclein: The substance discovered in the nucleus, later known as DNA, first isolated by Friedrich Miescher.

• DNA: Deoxyribonucleic acid, the molecule carrying genetic information in cells.

• Friedrich Miescher: Swiss biochemist who first isolated nuclein from pus cells in 1869.

• Chargaff: Discovered base pairing rules (A=T, G≡C) in DNA.

• Franklin: Rosalind Franklin obtained X-ray diffraction images of DNA, crucial for structure discovery.

• Mendel: Father of genetics, studied inheritance in pea plants but did not study DNA.

• Genetic material: Molecules responsible for storing and transmitting hereditary information.

• X-ray diffraction: Technique to study molecular structure used by Franklin for DNA.

Lead Question - 2020 (COVID Reexam)

The term 'Nuclein' for the genetic material was used by:

1. Franklin
2. Meischer
3. Chargaff
4. Mendel

Explanation: Friedrich Miescher first isolated a substance from the nucleus in 1869, which he called 'Nuclein'. This substance was later identified as DNA, the carrier of genetic information. Franklin, Chargaff, and Mendel contributed to DNA structure or genetics, but the term 'Nuclein' was coined by Miescher. Correct answer: Option 2.

1. Single Correct Answer MCQ:

Who discovered DNA base pairing rules?
1. Franklin
2. Miescher
3. Chargaff
4. Mendel

Explanation: Erwin Chargaff discovered that in DNA, adenine equals thymine and guanine equals cytosine, establishing base pairing rules essential for DNA structure. Franklin obtained X-ray diffraction images, Miescher discovered nuclein, and Mendel studied inheritance in pea plants. Answer: Option 3.

2. Single Correct Answer MCQ:

Which scientist used X-ray diffraction to study DNA?
1. Mendel
2. Franklin
3. Miescher
4. Chargaff

Explanation: Rosalind Franklin used X-ray diffraction to reveal DNA's helical structure, providing critical data for Watson and Crick's double helix model. Miescher isolated nuclein, Chargaff discovered base ratios, and Mendel worked on inheritance patterns. Answer: Option 2.

3. Single Correct Answer MCQ:

Who first isolated nuclein from cell nuclei?
1. Franklin
2. Miescher
3. Chargaff
4. Mendel

Explanation: Friedrich Miescher in 1869 isolated nuclein from the nuclei of pus cells. This nuclein was later identified as DNA. Franklin studied DNA structure, Chargaff discovered base ratios, and Mendel discovered inheritance laws. Answer: Option 2.

4. Single Correct Answer MCQ:

Nuclein later became known as:
1. RNA
2. Protein
3. DNA
4. Chromatin

Explanation: Nuclein isolated by Miescher was later identified as DNA, the hereditary material carrying genetic information. RNA, protein, and chromatin are cellular components but nuclein specifically refers to DNA. Answer: Option 3.

5. Single Correct Answer MCQ:

Which scientist studied pea plants and inheritance?
1. Miescher
2. Franklin
3. Mendel
4. Chargaff

Explanation: Gregor Mendel studied inheritance in pea plants, formulating laws of segregation and independent assortment. He did not study DNA. Miescher isolated nuclein, Franklin studied DNA structure, and Chargaff discovered base ratios. Answer: Option 3.

6. Single Correct Answer MCQ:

Which component is the genetic material in cells?
1. RNA
2. DNA
3. Protein
4. Lipid

Explanation: DNA is the genetic material in most cells, carrying hereditary information. RNA plays roles in protein synthesis, proteins perform structural and enzymatic functions, and lipids form membranes. Nuclein was an early term for DNA. Answer: Option 2.

7. Assertion-Reason MCQ:

Assertion (A): Miescher discovered nuclein in 1869.
Reason (R): Nuclein is composed of DNA and protein found in the nucleus.
1. Both A and R true, R correct explanation
2. Both A and R true, R not correct explanation
3. A true, R false
4. A false, R true

Explanation: Miescher discovered nuclein from nuclei, which contained DNA and some protein. Both assertion and reason are correct, and reason accurately explains the assertion. Answer: Option 1.

8. Matching Type MCQ:

Column I    Column II
(a) Miescher    (i) Base ratios in DNA
(b) Franklin    (ii) X-ray diffraction
(c) Chargaff    (iii) Isolated nuclein
(d) Mendel    (iv) Pea plant inheritance

1. (a)-(iii), (b)-(ii), (c)-(i), (d)-(iv)
2. (a)-(i), (b)-(iii), (c)-(ii), (d)-(iv)
3. (a)-(ii), (b)-(i), (c)-(iii), (d)-(iv)
4. (a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)

Explanation: Miescher isolated nuclein, Franklin studied DNA by X-ray diffraction, Chargaff discovered base ratios, Mendel studied inheritance. Correct matching: (a)-(iii), (b)-(ii), (c)-(i), (d)-(iv). Answer: Option 1.

9. Fill in the blanks:

The Swiss scientist who first coined the term 'Nuclein' is ________.
1. Franklin
2. Miescher
3. Chargaff
4. Mendel

Explanation: Friedrich Miescher, a Swiss biochemist, first isolated nuclein from cell nuclei and coined the term. This nuclein was later recognized as DNA, the carrier of genetic information. Franklin, Chargaff, and Mendel contributed to DNA structure or inheritance but did not name nuclein. Answer: Option 2.

10. Choose correct statements:

(a) Miescher isolated nuclein
(b) Nuclein is composed of DNA and protein
(c) Franklin discovered nuclein
(d) Mendel studied inheritance in pea plants

1. a, b, d only
2. a and c only
3. b and c only
4. All statements correct

Explanation: Miescher isolated nuclein containing DNA and protein. Mendel studied pea plant inheritance. Franklin did not discover nuclein but studied DNA structure. Therefore, correct statements are a, b, d only. Answer: Option 1.

Topic: Proteins, Carbohydrates, and Plant Hormones
Subtopic: Structure and Function of Biological Molecules

Keyword Definitions:

• Aquaporin: Integral membrane protein that facilitates water transport across membranes.

• Asparagine: Amino acid containing an amide functional group in its side chain.

• Abscisic acid (ABA): Plant hormone, belongs to carotenoids, involved in stress responses and seed dormancy.

• Chitin: Structural polysaccharide found in fungal cell walls and arthropod exoskeletons.

• Amide: Organic functional group containing -CONH2.

• Polysaccharide: Polymer of monosaccharides forming complex carbohydrates.

• Polypeptide: Chain of amino acids forming proteins.

• Carotenoids: Pigments involved in photosynthesis and photoprotection in plants.

Lead Question - 2020 (COVID Reexam)

Match the following :

(a) Aquaporin (i) Amide
(b) Asparagine (ii) Polysaccharide
(c) Abscisic acid (iii) Polypeptide
(d) Chitin (iv) Carotenoids

Select the correct option :

1. (a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)
2. (a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)
3. (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
4. (a)-(iii), (b)-(i), (c)-(ii), (d)-(iv)

Explanation: Aquaporin is a polypeptide forming water channels in membranes. Asparagine contains an amide group in its side chain. Abscisic acid is a carotenoid-derived plant hormone, and chitin is a polysaccharide. Therefore, the correct matching is option 1: (a)-(iii), (b)-(i), (c)-(iv), (d)-(ii), showing proper classification of biomolecules. (50 words)

Guessed Question 1. Aquaporins are classified as :

1. Lipids
2. Proteins
3. Polysaccharides
4. Nucleic acids

Explanation: Aquaporins are integral membrane proteins forming channels for water transport across biological membranes. They are not lipids, polysaccharides, or nucleic acids. They are crucial for water balance in cells and tissues. Therefore, the correct answer is option 2: Proteins. (50 words)

Guessed Question 2. Asparagine is an example of :

1. Aromatic amino acid
2. Amide-containing amino acid
3. Sulfur-containing amino acid
4. Non-polar amino acid

Explanation: Asparagine contains a side chain with an amide functional group (-CONH2). It is polar but uncharged, not aromatic or sulfur-containing. This property is important in protein folding and hydrogen bonding. Therefore, the correct answer is option 2: Amide-containing amino acid. (50 words)

Guessed Question 3. Abscisic acid is derived from :

1. Proteins
2. Polysaccharides
3. Carotenoids
4. Lipids

Explanation: Abscisic acid (ABA) is a plant hormone derived from carotenoid pigments. It regulates stress responses, seed dormancy, and stomatal closure. It is not derived from proteins, polysaccharides, or lipids directly. Correct answer is option 3: Carotenoids. (50 words)

Guessed Question 4. Chitin is a :

1. Protein
2. Polysaccharide
3. Lipid
4. Nucleic acid

Explanation: Chitin is a structural polysaccharide composed of N-acetylglucosamine units. It is found in fungal cell walls and arthropod exoskeletons. It is not a protein, lipid, or nucleic acid. Its rigidity provides structural support. Therefore, the correct answer is option 2: Polysaccharide. (50 words)

Guessed Question 5. Assertion-Reason Question:

Assertion (A): Aquaporins are made of polypeptides.
Reason (R): Polypeptides are polymers of amino acids forming proteins.
1. Both A and R true, R explains A
2. Both A and R true, R not correct explanation
3. A true, R false
4. A false, R true

Explanation: Aquaporins are membrane proteins composed of polypeptide chains. Polypeptides are indeed polymers of amino acids forming proteins. Both assertion and reason are true, and reason correctly explains the assertion. Therefore, correct answer is option 1. Polypeptide structure enables selective water transport in aquaporins. (50 words)

Guessed Question 6. Match the following:

(a) Cellulose (i) Structural polysaccharide
(b) Collagen (ii) Protein
(c) Starch (iii) Energy storage polysaccharide
(d) Hemoglobin (iv) Oxygen transport protein
1. (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
2. (a)-(ii), (b)-(i), (c)-(iii), (d)-(iv)
3. (a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)
4. (a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)

Explanation: Cellulose is a structural polysaccharide in plants. Collagen is a structural protein in connective tissues. Starch is a polysaccharide for energy storage. Hemoglobin is a protein for oxygen transport. Correct matching is option 1: (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv). This reflects biological molecule functions. (50 words)

Guessed Question 7. Fill in the blank:

Abscisic acid helps in ______ of seeds.

1. Germination
2. Dormancy
3. Growth
4. Photosynthesis

Explanation: Abscisic acid induces seed dormancy and inhibits premature germination. It helps seeds survive adverse conditions by controlling water loss and metabolic activity. It does not directly promote germination, growth, or photosynthesis. Therefore, the correct answer is option 2: Dormancy. (50 words)

Guessed Question 8. Choose correct statements:

1. Aquaporins are polypeptides.
2. Chitin is a polysaccharide.
3. Abscisic acid is a lipid.
4. Asparagine contains an amide group.
Options:
A. 1 and 2
B. 1, 2 and 4
C. 2 and 3
D. All 1, 2, 3, 4

Explanation: Aquaporins are polypeptides, chitin is a polysaccharide, and asparagine contains an amide group. Abscisic acid is derived from carotenoids, not a general lipid. Therefore, correct statements are 1, 2, and 4. The correct answer is option B. This demonstrates accurate classification of biomolecules. (50 words)

Topic: Amino Acids and Lipids
Subtopic: Structure and Functions

Keyword Definitions:

• Amino acids: Organic molecules with amino and carboxyl groups forming proteins.

• Sulphur: An essential element present in certain amino acids like cysteine and methionine.

• Lipids: Hydrophobic molecules including fats, oils, phospholipids, and steroids.

• Lecithin: A phospholipid containing choline, phosphate, and fatty acids.

• Aromatic amino acids: Amino acids like tyrosine, tryptophan, and phenylalanine with aromatic rings.

Lead Question - 2020 (COVID Reexam)

Identify the statement which is incorrect.

1. Sulphur is an integral part of cysteine.
2. Glycine is an example of lipids.
3. Lecithin contains a phosphorus atom in its structure.
4. Tyrosine possesses an aromatic ring in its structure.

Explanation: The incorrect statement is option 2. Glycine is the simplest amino acid, not a lipid. Sulphur is present in cysteine, lecithin has phosphorus, and tyrosine has an aromatic ring. Amino acids are protein building blocks, while lipids are separate biomolecules. Correct answer is Glycine is not lipid. (50 words)

1. Which amino acid contains sulphur?

1. Valine
2. Cysteine
3. Glycine
4. Alanine

Explanation: The amino acid cysteine contains sulphur in its side chain. Sulphur helps in disulfide bond formation, providing structural stability to proteins. Other amino acids like glycine, valine, and alanine do not contain sulphur. Thus, cysteine plays a key role in protein folding and function. Correct answer is cysteine. (50 words)

2. Glycine is classified as:

1. Non-polar amino acid
2. Simplest amino acid
3. Essential amino acid
4. Aromatic amino acid

Explanation: Glycine is the simplest amino acid with a single hydrogen atom as its side chain. It is a non-essential amino acid and not aromatic. It contributes flexibility to protein structures due to its small size. Correct classification of glycine is the simplest amino acid. Correct answer is option 2. (50 words)

3. Lecithin belongs to which biomolecule category?

1. Steroids
2. Phospholipids
3. Proteins
4. Amino acids

Explanation: Lecithin is a phospholipid commonly found in biological membranes. It contains fatty acids, phosphate, and choline groups. It helps in maintaining membrane fluidity and also acts as an emulsifier in food industries. It is not a protein or amino acid. The correct answer is phospholipids. (50 words)

4. Which amino acid has an aromatic ring?

1. Tyrosine
2. Glycine
3. Serine
4. Threonine

Explanation: Tyrosine contains a phenolic aromatic ring in its side chain. This makes it an aromatic amino acid, along with tryptophan and phenylalanine. Aromatic amino acids absorb UV light and play important roles in protein structure and enzyme activity. Correct answer is Tyrosine. (50 words)

5. Assertion-Reason Question:

Assertion (A): Cysteine can form disulfide bonds.
Reason (R): Glycine has a sulfur atom in its structure.
1. Both A and R are true, R is correct explanation.
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: Cysteine forms disulfide bonds due to its thiol (-SH) group, stabilizing proteins. Glycine does not contain sulfur, so the reason is false. Therefore, A is true and R is false. This distinction is essential in protein chemistry. Correct answer is option 3. (50 words)

6. Matching Type Question:

Match the following:
(a) Phenylalanine (i) Phospholipid
(b) Lecithin (ii) Aromatic amino acid
(c) Methionine (iii) Sulfur-containing amino acid
(d) Cholesterol (iv) Steroid
1. (a)-(ii), (b)-(i), (c)-(iii), (d)-(iv)
2. (a)-(iii), (b)-(ii), (c)-(iv), (d)-(i)
3. (a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)
4. (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)

Explanation: Phenylalanine is an aromatic amino acid. Lecithin is a phospholipid. Methionine is a sulfur-containing amino acid. Cholesterol is a steroid. Thus, correct matching is (a)-(ii), (b)-(i), (c)-(iii), (d)-(iv). This classification highlights major biomolecules and their importance in structure and metabolism. Correct answer is option 1. (50 words)

7. Fill in the Blank:

The simplest amino acid with hydrogen as side chain is ________.

1. Alanine
2. Glycine
3. Valine
4. Proline

Explanation: Glycine has hydrogen as its side chain, making it the simplest amino acid. Its small size provides flexibility to proteins and helps in the formation of tight turns. Other amino acids have bulkier side chains. Therefore, the correct answer is glycine. Correct answer is option 2. (50 words)

8. Choose the correct statements:

1. Lecithin is a protein.
2. Tyrosine has an aromatic ring.
3. Glycine is a lipid.
4. Cysteine contains sulphur.
Options:
A. 1 and 2
B. 2 and 3
C. 2 and 4
D. 1 and 3

Explanation: Correct statements are that Tyrosine has an aromatic ring and Cysteine contains sulphur. Lecithin is not a protein but a phospholipid, and Glycine is an amino acid not lipid. Therefore, the right choice is option C (2 and 4). Correct answer is option C. (50 words)

Topic: Carbohydrates & Proteins

Subtopic: Glycosidic and Peptide Bonds

Keyword Definitions:

• Glycosidic bond – Covalent bond linking carbohydrate monomers in polysaccharides.

• Peptide bond – Covalent bond linking amino acids in proteins or peptides.

• Cellulose – Polysaccharide of β-glucose units with glycosidic linkages, structural component of plant cell wall.

• Inulin – Polysaccharide composed of fructose units, used as storage carbohydrate in plants.

• Insulin – Peptide hormone regulating blood glucose, composed of amino acids linked by peptide bonds.

• Chitin – Polysaccharide forming fungal cell walls and exoskeletons of arthropods.

• Trypsin – Digestive protease enzyme composed of amino acids linked via peptide bonds.

Lead Question - 2020

Identify the substances having glycosidic bond and peptide bond, respectively in their structure:
(1) Cellulose, lecithin
(2) Inulin, insulin
(3) Chitin, cholesterol
(4) Glycerol, trypsin

Explanation: Inulin is a polysaccharide containing glycosidic bonds, while insulin is a peptide hormone composed of amino acids connected by peptide bonds. This combination correctly represents glycosidic and peptide bonds. Correct answer is (2) Inulin, insulin.

1. Single Correct Answer: Which of the following contains glycosidic bonds?
(1) Glucose
(2) Starch
(3) Alanine
(4) Urea

Explanation: Starch is a polysaccharide made of glucose units linked by glycosidic bonds. Correct answer is (2) Starch.

2. Single Correct Answer: The bond linking amino acids in proteins is:
(1) Glycosidic
(2) Hydrogen
(3) Peptide
(4) Phosphodiester

Explanation: Peptide bonds are covalent bonds formed between amino acids in proteins, essential for polypeptide chains. Correct answer is (3) Peptide.

3. Single Correct Answer: Chitin is composed of:
(1) Amino acids
(2) Fructose units
(3) N-acetylglucosamine units
(4) Glycerol

Explanation: Chitin is a polysaccharide of N-acetylglucosamine linked by glycosidic bonds forming fungal cell walls and arthropod exoskeletons. Correct answer is (3) N-acetylglucosamine units.

4. Assertion-Reason:
Assertion (A): Insulin is a protein.
Reason (R): It contains amino acids linked by peptide bonds.
(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: Insulin is a peptide hormone composed of amino acids joined by peptide bonds, making both the assertion and reason correct and reason explains assertion. Correct answer is (1).

5. Single Correct Answer: Which polysaccharide is used as a storage carbohydrate in plants?
(1) Insulin
(2) Inulin
(3) Collagen
(4) Trypsin

Explanation: Inulin is a plant storage polysaccharide composed of fructose units linked by glycosidic bonds. Correct answer is (2) Inulin.

6. Single Correct Answer: The peptide hormone regulating blood sugar is:
(1) Glucagon
(2) Insulin
(3) Starch
(4) Chitin

Explanation: Insulin is a peptide hormone that regulates blood glucose levels, consisting of amino acids linked by peptide bonds. Correct answer is (2) Insulin.

7. Matching Type: Match Column I with Column II:
a. Polysaccharide – i. Inulin
b. Protein hormone – ii. Insulin
c. Structural polysaccharide – iii. Chitin
d. Enzyme – iv. Trypsin
(1) a-i, b-ii, c-iii, d-iv
(2) a-iii, b-i, c-iv, d-ii
(3) a-iv, b-iii, c-ii, d-i
(4) a-ii, b-iv, c-i, d-iii

Explanation: Inulin is a polysaccharide (a-i), insulin is a protein hormone (b-ii), chitin is a structural polysaccharide (c-iii), and trypsin is an enzyme (d-iv). Correct answer is (1).

8. Fill in the blank: _______ is a polysaccharide composed of fructose units linked by glycosidic bonds.
(1) Inulin
(2) Insulin
(3) Chitin
(4) Collagen

Explanation: Inulin is a polysaccharide of fructose units connected via glycosidic bonds and serves as a storage carbohydrate in plants. Correct answer is (1) Inulin.

9. Single Correct Answer: Which of the following contains peptide bonds?
(1) Inulin
(2) Insulin
(3) Cellulose
(4) Chitin

Explanation: Insulin is a peptide hormone composed of amino acids linked by peptide bonds, forming its functional structure. Correct answer is (2) Insulin.

10. Choose the correct statements:
(a) Glycosidic bonds link monosaccharides
(b) Peptide bonds link amino acids
(c) Inulin is a polysaccharide
(d) Insulin is a protein hormone
(1) a, b, c, d
(2) a, c, d
(3) b, d
(4) a, b, c

Explanation: All four statements are correct: glycosidic bonds link monosaccharides (a), peptide bonds link amino acids (b), inulin is a polysaccharide (c), and insulin is a protein hormone (d). Correct answer is (1) a, b, c, d.

Topic: Biomolecules and Enzyme Inhibitors

Subtopic: Enzyme Inhibition & Structural Components

Keyword Definitions:

• Inhibitor of catalytic activity – A molecule that decreases or stops the activity of an enzyme, preventing substrate conversion to product.

• Peptide bonds – Covalent bonds linking amino acids in proteins or polypeptides.

• Chitin – Structural polysaccharide forming the cell wall in fungi and exoskeletons of arthropods.

• Secondary metabolite – Organic compounds not directly involved in normal growth, development, or reproduction, often involved in defense, e.g., toxins.

• Ricin – Toxic protein from castor bean that inhibits protein synthesis.

• Malonate – Competitive inhibitor of succinate dehydrogenase in the citric acid cycle.

• Collagen – Structural protein abundant in connective tissues, providing strength and support.

Lead Question - 2020

Match the following:
(a) Inhibitor of catalytic activity
(b) Possess peptide bonds
(c) Cell wall material in fungi
(d) Secondary metabolite
(i) Ricin
(ii) Malonate
(iii) Chitin
(iv) Collagen
Choose the correct option:
(A) a-iii, b-iv, c-i, d-ii
(B) a-ii, b-iii, c-i, d-iv
(C) a-ii, b-iv, c-iii, d-i
(D) a-iii, b-i, c-iv, d-ii

Explanation: Malonate is an inhibitor of catalytic activity (a-ii). Collagen contains peptide bonds (b-iv). Chitin forms the cell wall in fungi (c-iii). Ricin is a secondary metabolite (d-i) acting as a toxin. Correct answer is (C) a-ii, b-iv, c-iii, d-i.

1. Single Correct Answer: Which of the following is a competitive inhibitor of succinate dehydrogenase?
(1) Ricin
(2) Malonate
(3) Chitin
(4) Collagen

Explanation: Malonate competitively inhibits succinate dehydrogenase in the citric acid cycle, blocking substrate binding. Correct answer is (2) Malonate.

2. Single Correct Answer: Proteins are characterized by which bond linking amino acids?
(1) Glycosidic bonds
(2) Phosphodiester bonds
(3) Peptide bonds
(4) Hydrogen bonds

Explanation: Peptide bonds are covalent links between amino acids in proteins, essential for polypeptide formation. Correct answer is (3) Peptide bonds.

3. Single Correct Answer: The structural polysaccharide forming fungal cell walls is:
(1) Cellulose
(2) Chitin
(3) Starch
(4) Glycogen

Explanation: Chitin is a polymer of N-acetylglucosamine forming rigid fungal cell walls. Correct answer is (2) Chitin.

4. Assertion-Reason:
Assertion (A): Ricin is a toxic protein.
Reason (R): Ricin inhibits protein synthesis in target cells.
(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: Ricin is a secondary metabolite toxin that inhibits protein synthesis, making both statements correct and the reason explains the assertion. Correct answer is (1).

5. Single Correct Answer: Collagen is an example of:
(1) Structural protein
(2) Enzyme inhibitor
(3) Secondary metabolite
(4) Polysaccharide

Explanation: Collagen is a structural protein in connective tissue, rich in peptide bonds, providing tensile strength. Correct answer is (1) Structural protein.

6. Single Correct Answer: Secondary metabolites are primarily involved in:
(1) Growth and reproduction
(2) Defense and competition
(3) Energy production
(4) Protein synthesis

Explanation: Secondary metabolites, like ricin, are not required for growth but help in defense, interspecies competition, and ecological interactions. Correct answer is (2) Defense and competition.

7. Matching Type: Match Column I with Column II:
a. Enzyme inhibitor – i. Malonate
b. Structural protein – ii. Collagen
c. Fungal cell wall – iii. Chitin
d. Toxic secondary metabolite – iv. Ricin
(1) a-i, b-ii, c-iii, d-iv
(2) a-iv, b-i, c-ii, d-iii
(3) a-iii, b-iv, c-i, d-ii
(4) a-ii, b-iii, c-iv, d-i

Explanation: Malonate inhibits enzymes (a-i), collagen is a structural protein (b-ii), chitin forms fungal cell walls (c-iii), and ricin is a toxic secondary metabolite (d-iv). Correct answer is (1).

8. Fill in the blank: _______ is a polymer forming fungal cell walls.
(1) Chitin
(2) Collagen
(3) Malonate
(4) Ricin

Explanation: Chitin, a long-chain polymer of N-acetylglucosamine, provides rigidity to fungal cell walls. Correct answer is (1) Chitin.

9. Single Correct Answer: Which compound inhibits succinate dehydrogenase competitively?
(1) Ricin
(2) Malonate
(3) Chitin
(4) Collagen

Explanation: Malonate acts as a competitive inhibitor of succinate dehydrogenase, blocking substrate access to the enzyme's active site. Correct answer is (2) Malonate.

10. Choose the correct statements:
(a) Collagen contains peptide bonds
(b) Chitin is structural polysaccharide in fungi
(c) Ricin is a secondary metabolite toxin
(d) Malonate is an enzyme inhibitor
(1) a, b, c, d
(2) a, b, d
(3) b, c, d
(4) a, c, d

Explanation: All four statements are correct: collagen has peptide bonds (a), chitin is structural (b), ricin is a secondary metabolite toxin (c), and malonate is an enzyme inhibitor (d). Correct answer is (1) a, b, c, d.

Topic: Protein Synthesis

Subtopic: Translation

Keyword Definitions:

• Translation – Process by which mRNA is decoded by ribosomes to synthesize proteins.

• tRNA – Transfer RNA, brings specific amino acids to the ribosome during translation.

• Aminoacylation – Attachment of an amino acid to its corresponding tRNA by aminoacyl-tRNA synthetase.

• Anti-codon – Three-nucleotide sequence on tRNA complementary to codon on mRNA.

• mRNA – Messenger RNA, carries genetic code from DNA to ribosome for protein synthesis.

• Ribosome – Cellular machinery that reads mRNA and assembles amino acids into a polypeptide chain.

Lead Question - 2020

The first phase of translation is:
(1) Aminoacylation of tRNA
(2) Recognition of an anti-codon
(3) Binding of mRNA to ribosome
(4) Recognition of DNA molecule

Explanation: Translation begins with aminoacylation of tRNA, which attaches a specific amino acid to its tRNA via aminoacyl-tRNA synthetase. This step is essential before codon-anticodon recognition and ribosome binding. DNA recognition is irrelevant at this stage. Correct answer is (1) Aminoacylation of tRNA.

1. Single Correct Answer: The codon-anticodon pairing occurs at:
(1) Ribosome A site
(2) Ribosome P site
(3) Ribosome E site
(4) Nucleus

Explanation: During translation, codon-anticodon recognition occurs at the ribosome A site where tRNA binds complementary to mRNA codon. Correct answer is (1).

2. Single Correct Answer: The enzyme responsible for aminoacylation is:
(1) RNA polymerase
(2) Aminoacyl-tRNA synthetase
(3) Ligase
(4) Helicase

Explanation: Aminoacyl-tRNA synthetase catalyzes the attachment of specific amino acids to their tRNAs, forming aminoacyl-tRNA, which is the first step in translation. Correct answer is (2).

3. Single Correct Answer: Start codon on mRNA is:
(1) UAG
(2) AUG
(3) UAA
(4) UGA

Explanation: AUG codon on mRNA codes for methionine and acts as the start codon for translation initiation. Correct answer is (2).

4. Assertion (A): Aminoacylation of tRNA is essential before translation.
Reason (R): tRNA without amino acid cannot bind ribosome.
(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: tRNA must be charged with amino acid before entering translation. Uncharged tRNA cannot deliver amino acids to ribosome, so R explains A. Correct answer is (1).

5. Single Correct Answer: The ribosome binding site on mRNA is called:
(1) Shine-Dalgarno sequence
(2) Poly-A tail
(3) 5’ cap only
(4) Intron

Explanation: The Shine-Dalgarno sequence in prokaryotic mRNA guides ribosome binding at the start codon. Correct answer is (1).

6. Single Correct Answer: The A site of ribosome is responsible for:
(1) Exit of tRNA
(2) Aminoacyl-tRNA entry
(3) Peptide bond formation
(4) mRNA transcription

Explanation: Aminoacyl-tRNA enters the ribosome at A site to pair with codon on mRNA. Correct answer is (2).

7. Matching Type: Match column I with column II:
a. tRNA charging – i. Aminoacylation
b. Start codon – ii. AUG
c. Ribosome site for new tRNA – iii. A site
d. Polypeptide exit – iv. P site
(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: tRNA charging corresponds to aminoacylation (a-i), start codon is AUG (b-ii), A site accepts new tRNA (c-iii), P site holds growing polypeptide (d-iv). Correct answer is (1).

8. Fill in the blank: The first amino acid incorporated during translation in eukaryotes is ______.
(1) Methionine
(2) Formyl-methionine
(3) Leucine
(4) Glycine

Explanation: In eukaryotes, translation begins with methionine incorporated by initiator tRNA. Correct answer is (1).

9. Single Correct Answer: Which molecule carries amino acid to ribosome?
(1) mRNA
(2) tRNA
(3) rRNA
(4) DNA

Explanation: tRNA transports specific amino acids to the ribosome, facilitating translation. Correct answer is (2).

10. Choose the correct statements:
(a) Translation begins with aminoacylation of tRNA
(b) Start codon is AUG
(c) DNA is directly involved in translation
(d) Ribosome has A, P, and E sites
(1) a, b, d only
(2) a, c, d only
(3) b, c, d only
(4) a, b, c only

Explanation: Translation requires tRNA aminoacylation (a), AUG start codon (b), and ribosome sites A, P, E (d). DNA is not directly involved. Correct answer is (1) a, b, d only.

Topic: Carbohydrates

Subtopic: Polysaccharides in Algae

Keyword Definitions:

• Floridean starch – Storage polysaccharide found in red algae, similar to glycogen and amylopectin.

• Amylopectin – Branched polymer of glucose, component of plant starch.

• Glycogen – Branched glucose polymer, energy storage in animals and fungi.

• Starch – Plant polysaccharide for energy storage, composed of amylose and amylopectin.

• Cellulose – Linear polymer of glucose forming plant cell walls.

• Polysaccharide – Long-chain carbohydrate composed of monosaccharide units linked by glycosidic bonds.

Lead Question - 2020

Floridean starch has structure similar to :

(1) Mannitol and algin
(2) Laminarin and cellulose
(3) Starch and cellulose
(4) Amylopectin and glycogen

Explanation: Floridean starch is a branched polysaccharide found in red algae and is structurally similar to amylopectin and glycogen, providing energy storage. Unlike starch in plants, it is more highly branched. Correct answer is (4) Amylopectin and glycogen.

1. Single Correct Answer: Which of the following is the main storage carbohydrate in red algae?
(1) Laminarin
(2) Floridean starch
(3) Starch
(4) Glycogen

Explanation: Red algae store energy mainly in the form of Floridean starch, a branched polymer of glucose similar to glycogen. Correct answer is (2) Floridean starch.

2. Single Correct Answer: Amylopectin is:
(1) Linear glucose polymer
(2) Branched glucose polymer
(3) Fructose polymer
(4) Protein-linked sugar

Explanation: Amylopectin is a branched polymer of glucose forming part of plant starch, providing a compact structure for energy storage. Correct answer is (2) Branched glucose polymer.

3. Single Correct Answer: Glycogen differs from starch by:
(1) Being linear
(2) Being more highly branched
(3) Containing fructose
(4) Being unbranched

Explanation: Glycogen is more highly branched than starch and amylopectin, allowing rapid mobilization of glucose for energy in animals. Correct answer is (2) Being more highly branched.

4. Assertion (A): Floridean starch is similar to glycogen.
Reason (R): It is a highly branched polysaccharide stored in cytoplasm.
(1) Both A and R true and R explains A
(2) Both A and R true but R does not explain A
(3) A true, R false
(4) A false, R true

Explanation: Floridean starch is a highly branched cytoplasmic polysaccharide, similar in structure and function to glycogen. Both Assertion and Reason are true, and R correctly explains A. Correct answer is (1).

5. Single Correct Answer: Starch is composed of:
(1) Amylose only
(2) Amylopectin only
(3) Amylose and amylopectin
(4) Glycogen and amylopectin

Explanation: Starch in plants consists of two glucose polymers, linear amylose and branched amylopectin, providing compact energy storage. Correct answer is (3) Amylose and amylopectin.

6. Single Correct Answer: Laminarin is found in:
(1) Red algae
(2) Brown algae
(3) Green algae
(4) Cyanobacteria

Explanation: Laminarin is a storage polysaccharide in brown algae, consisting of β-glucose units, unlike Floridean starch in red algae. Correct answer is (2) Brown algae.

7. Match the polysaccharide with its source:
a. Floridean starch – i. Red algae
b. Laminarin – ii. Brown algae
c. Starch – iii. Green plants
d. Glycogen – iv. Animals
(1) a-i, b-ii, c-iii, d-iv
(2) a-ii, b-i, c-iii, d-iv
(3) a-iii, b-ii, c-i, d-iv
(4) a-i, b-iii, c-ii, d-iv

Explanation: Floridean starch is found in red algae (a-i), laminarin in brown algae (b-ii), starch in green plants (c-iii), and glycogen in animals (d-iv). Correct answer is (1).

8. Fill in the blank: The storage polysaccharide in red algae is called ______.
(1) Laminarin
(2) Floridean starch
(3) Glycogen
(4) Amylose

Explanation: Red algae store energy in the form of Floridean starch, a branched glucose polymer similar to glycogen. Correct answer is (2) Floridean starch.

9. Single Correct Answer: Cellulose differs from starch in that it:
(1) Is branched
(2) Has α-glucose linkages
(3) Has β-glucose linkages forming linear chains
(4) Stores energy

Explanation: Cellulose is composed of β-glucose linked in linear chains, forming structural material in plant cell walls, unlike starch which is for energy storage. Correct answer is (3) Has β-glucose linkages forming linear chains.

10. Choose the correct statements:
(a) Floridean starch is similar to amylopectin
(b) Glycogen is highly branched
(c) Laminarin is found in red algae
(d) Starch consists of amylose and amylopectin
(1) a, b, d only
(2) a, b, c, d
(3) b, c, d only
(4) a, c, d only

Explanation: Floridean starch resembles amylopectin (a), glycogen is highly branched (b), starch consists of amylose and amylopectin (d). Laminarin is from brown algae, so c is incorrect. Correct answer is (1) a, b, d only.

Subtopic: Enzyme Activation

• Enterokinase: Enzyme secreted by intestinal cells that activates trypsinogen into trypsin.

• Trypsinogen: Inactive precursor of trypsin produced by the pancreas.

• Trypsin: Active enzyme that digests proteins into polypeptides in the small intestine.

• Pepsinogen: Inactive precursor of pepsin, secreted by stomach lining.

• Pepsin: Active enzyme that breaks down proteins into peptides in the stomach.

• Caseinogen: Milk protein precursor converted into casein by rennin.

• Casein: Milk protein formed from caseinogen, essential in dairy digestion.

• Protein digestion: Process of breaking proteins into peptides and amino acids using enzymes.

• Polypeptides: Chains of amino acids formed during protein digestion.

• Activation of zymogens: Conversion of inactive enzyme precursors into active enzymes.

• Small intestine: Site where trypsinogen is activated by enterokinase for protein digestion.

Lead Question (2020): The enzyme enterokinase helps conversion of :

1. Caseinogen into casein

2. Pepsinogen into pepsin

3. Protein into polypeptides

4. Trypsinogen into trypsin

Explanation: The correct answer is 4. Enterokinase is secreted by the intestinal mucosa and converts the inactive pancreatic enzyme trypsinogen into active trypsin. Trypsin then digests proteins into polypeptides. Other options refer to enzymes activated by different mechanisms, such as pepsinogen to pepsin in the stomach.

Guessed MCQs:

1. Question 1: Which organ secretes trypsinogen?
   A. Stomach
   B. Small intestine
   C. Pancreas
   D. Liver
   Explanation: The correct answer is C. Trypsinogen is secreted by the pancreas as an inactive zymogen. It is activated by enterokinase in the small intestine to form trypsin, which digests dietary proteins into polypeptides.

2. Question 2: Pepsinogen is activated by:
   A. Enterokinase
   B. Acidic environment of stomach
   C. Trypsin
   D. Rennin
   Explanation: The correct answer is B. Pepsinogen, secreted by gastric chief cells, is activated to pepsin by the acidic pH in the stomach. Enterokinase does not activate pepsinogen; it specifically activates trypsinogen in the small intestine.

3. Question 3: Trypsin digests proteins into:
   A. Amino acids only
   B. Polypeptides
   C. Casein
   D. Pepsinogen
   Explanation: The correct answer is B. Trypsin, once activated from trypsinogen by enterokinase, breaks down proteins into smaller polypeptide chains, which are later further digested into amino acids by other proteases.

4. Question 4: Enterokinase is produced by:
   A. Pancreas
   B. Gastric glands
   C. Intestinal mucosa
   D. Liver
   Explanation: The correct answer is C. Enterokinase is secreted by the cells of the small intestine lining. It activates trypsinogen into trypsin, initiating protein digestion in the intestine, independent of gastric enzymes.

5. Question 5: Caseinogen is converted into casein by:
   A. Enterokinase
   B. Rennin
   C. Trypsin
   D. Pepsin
   Explanation: The correct answer is B. Caseinogen is the milk protein precursor converted into casein by rennin (chymosin) in the stomach. Enterokinase does not act on caseinogen; it specifically activates trypsinogen.

6. Question 6: Which is an inactive enzyme precursor?
   A. Trypsin
   B. Trypsinogen
   C. Pepsin
   D. Rennin
   Explanation: The correct answer is B. Trypsinogen is an inactive zymogen secreted by the pancreas. Enterokinase converts it into active trypsin for protein digestion in the small intestine.

7. Question 7: Assertion-Reason:
   Assertion (A): Enterokinase is essential for protein digestion.
   Reason (R): It converts trypsinogen into trypsin which digests proteins.
   A. Both A and R are true, R is correct explanation of A
   B. Both A and R are true, R is not correct explanation of A
   C. A is true, R is false
   D. A is false, R is true
   Explanation: The correct answer is A. Enterokinase activates trypsinogen to trypsin. Trypsin then digests proteins into polypeptides, making enterokinase essential for initiating protein digestion in the small intestine.

8. Question 8: Matching Type: Match enzyme precursor with activator:
   i. Trypsinogen - A. Enterokinase
   ii. Pepsinogen - B. HCl
   iii. Caseinogen - C. Rennin
   Choices:
   A. i-A, ii-B, iii-C
   B. i-B, ii-A, iii-C
   C. i-C, ii-B, iii-A
   D. i-A, ii-C, iii-B
   Explanation: The correct answer is A. Trypsinogen is activated by enterokinase, pepsinogen by stomach acid (HCl), and caseinogen by rennin. This illustrates enzyme activation mechanisms in protein digestion.

9. Question 9: Fill in the Blanks: Enterokinase converts ________ into trypsin.
   A. Pepsinogen
   B. Trypsinogen
   C. Caseinogen
   D. Rennin
   Explanation: The correct answer is B. Enterokinase converts inactive trypsinogen into active trypsin in the small intestine. This activation is crucial for protein digestion into polypeptides.

10. Question 10: Choose the correct statements:
    i. Enterokinase activates trypsinogen
    ii. Trypsin digests proteins into polypeptides
    iii. Pepsinogen is activated by enterokinase
    iv. Caseinogen is converted into casein by rennin
    A. i, ii, iv
    B. i, iii
    C. ii, iii
    D. i, ii, iii, iv
    Explanation: The correct answer is A. Enterokinase activates trypsinogen to trypsin. Trypsin digests proteins into polypeptides. Caseinogen is converted to casein by rennin. Pepsinogen is activated by stomach acid, not enterokinase, making statements i, ii, iv correct.

Subtopic: Functions of Secondary Metabolites

• Secondary metabolites: Organic compounds not directly involved in growth or reproduction but important for plant survival and interactions.

• Nicotine: Alkaloid produced by tobacco plants as a defense against herbivores.

• Strychnine: Toxic alkaloid from Strychnos nux-vomica used by plants for defense.

• Caffeine: Alkaloid from coffee and tea plants that deters herbivores and inhibits competitor plants.

• Defense action: Mechanisms plants use to protect against herbivores, pathogens, and competitors.

• Reproduction effect: Influence of chemicals on pollination or seed production.

• Nutritive value: Compounds providing energy or essential nutrients to the organism.

• Growth response: Physiological changes in plants due to environmental stimuli or chemicals.

• Alkaloids: Nitrogen-containing secondary metabolites with potent biological effects.

• Plant survival strategy: Adaptations including secondary metabolites that enhance plant fitness.

• Allelopathy: Chemical inhibition of one plant species by another through secondary metabolites.

Lead Question (2020): Secondary metabolites such as nicotine, strychnine and caffeine are produced by plants for their :

1. Defence action

2. Effect on reproduction

3. Nutritive value

4. Growth response

Explanation: The correct answer is 1. Secondary metabolites like nicotine, strychnine, and caffeine are produced by plants primarily for defense against herbivores, pathogens, and competing plants. They do not directly contribute to growth or reproduction but enhance plant survival by providing chemical protection and deterring threats.

Guessed MCQs:

1. Question 1: Alkaloids in plants serve primarily to:
   A. Promote growth
   B. Provide nutrition
   C. Defend against herbivores
   D. Stimulate reproduction
   Explanation: The correct answer is C. Alkaloids are secondary metabolites produced to protect plants from herbivores and pathogens. Nicotine, caffeine, and strychnine are examples of defensive alkaloids that enhance survival by deterring consumption and providing chemical protection.

2. Question 2: Caffeine acts in plants as:
   A. Growth hormone
   B. Allelopathic agent
   C. Nutrient
   D. Pollinator attractant
   Explanation: The correct answer is B. Caffeine is an allelopathic secondary metabolite that inhibits the growth of neighboring plants and deters herbivores, thereby providing a competitive advantage and protecting the plant from predation.

3. Question 3: Nicotine is produced in:
   A. Roots of coffee plants
   B. Leaves of tobacco plants
   C. Seeds of Strychnos
   D. Flowers of tea plants
   Explanation: The correct answer is B. Nicotine is synthesized in the leaves of tobacco plants as a chemical defense against herbivores. It is toxic to many insects and animals, reducing damage to plant tissues.

4. Question 4: Strychnine is an example of a:
   A. Carbohydrate
   B. Protein
   C. Toxic alkaloid
   D. Phenolic compound
   Explanation: The correct answer is C. Strychnine is a toxic alkaloid produced by Strychnos nux-vomica. It functions as a secondary metabolite, protecting the plant against herbivores and pathogens by its poisonous effects.

5. Question 5: Secondary metabolites are generally:
   A. Directly involved in growth
   B. Non-essential for basic metabolism
   C. Main source of energy
   D. Structural components of cells
   Explanation: The correct answer is B. Secondary metabolites are not essential for primary metabolic processes like growth or reproduction but provide ecological advantages such as defense, allelopathy, and adaptation to environmental stresses.

6. Question 6: Which of the following is not a secondary metabolite?
   A. Nicotine
   B. Caffeine
   C. Glucose
   D. Strychnine
   Explanation: The correct answer is C. Glucose is a primary metabolite involved in energy production. Nicotine, caffeine, and strychnine are secondary metabolites produced for defense, providing chemical protection without directly affecting primary metabolism.

7. Question 7: Assertion-Reason:
   Assertion (A): Plants produce caffeine as a defense chemical.
   Reason (R): Caffeine deters herbivores and inhibits competitor plant growth.
   A. Both A and R are true, R is correct explanation of A
   B. Both A and R are true, R is not correct explanation of A
   C. A is true, R is false
   D. A is false, R is true
   Explanation: The correct answer is A. Caffeine is a secondary metabolite acting as a defense compound. It deters herbivores and inhibits the germination of competing plant species nearby, enhancing the survival and competitive advantage of the producing plant.

8. Question 8: Matching Type: Match the metabolite with its plant source:
   i. Nicotine - A. Tobacco
   ii. Caffeine - B. Coffee/Tea
   iii. Strychnine - C. Strychnos nux-vomica
   Choices:
   A. i-A, ii-B, iii-C
   B. i-B, ii-A, iii-C
   C. i-C, ii-B, iii-A
   D. i-A, ii-C, iii-B
   Explanation: The correct answer is A. Nicotine is produced in tobacco, caffeine in coffee and tea plants, and strychnine in Strychnos nux-vomica. Correct matching illustrates the plant-specific production of secondary metabolites for defense.

9. Question 9: Fill in the Blanks: Secondary metabolites like nicotine, strychnine, and caffeine primarily provide ________ to plants.
   A. Nutrients
   B. Defense against herbivores
   C. Growth hormones
   D. Reproductive signals
   Explanation: The correct answer is B. Secondary metabolites serve as chemical defense compounds, deterring herbivores, pathogens, and competitor plants. They enhance survival without directly participating in growth or reproduction.

10. Question 10: Choose the correct statements:
    i. Nicotine is toxic to herbivores
    ii. Caffeine inhibits competitor plant growth
    iii. Strychnine is a primary metabolite
    iv. Secondary metabolites help plant defense
    A. i, ii, iv
    B. i, iii
    C. ii, iii
    D. i, ii, iii, iv
    Explanation: The correct answer is A. Nicotine and strychnine are toxic alkaloids; caffeine inhibits competitor plants. All are secondary metabolites enhancing plant defense. Strychnine is not a primary metabolite. Correct statements reflect the ecological role of secondary metabolites in plant survival.

Chapter: Genetics and Molecular Biology

Topic: DNA Structure and Function

Subtopic: Base Pairing and Hydrogen Bonds

• Adenine: Purine nitrogenous base in DNA pairing with thymine via hydrogen bonds.

• Thymine: Pyrimidine base in DNA pairing with adenine through hydrogen bonds.

• Guanine: Purine base in DNA pairing with cytosine through three hydrogen bonds.

• Cytosine: Pyrimidine base in DNA pairing with guanine via hydrogen bonds.

• Hydrogen bonds: Weak bonds between complementary bases stabilizing DNA double helix.

• Base pairing: Specific pairing of purines with pyrimidines: A-T and G-C.

• Double helix: Twisted ladder-like structure of DNA formed by sugar-phosphate backbone and base pairs.

• Purines: Nitrogenous bases with two rings, adenine and guanine.

• Pyrimidines: Nitrogenous bases with one ring, thymine and cytosine.

• Complementary strands: DNA strands with paired bases ensuring genetic information accuracy.

• DNA stability: Maintained by hydrogen bonds and base stacking interactions.

Lead Question (2020): Which of the following statements is correct?

1. Adenine pairs with thymine through three H-bonds

2. Adenine does not pair with thymine

3. Adenine pairs with thymine through two H-bonds

4. Adenine pairs with thymine through one H-bond

Explanation: The correct answer is 3. Adenine (A) pairs with thymine (T) in DNA through two hydrogen bonds. This complementary base pairing ensures the stability and fidelity of the double helix. Guanine pairs with cytosine via three hydrogen bonds, and these specific interactions maintain DNA’s structural integrity.

Guessed MCQs:

1. Question 1: Which base pairs with guanine in DNA?
   A. Adenine
   B. Thymine
   C. Cytosine
   D. Uracil
   Explanation: The correct answer is C. Cytosine pairs with guanine through three hydrogen bonds. This pairing ensures proper double helix formation. Adenine pairs with thymine, while uracil replaces thymine in RNA, maintaining complementary base interactions in nucleic acids.

2. Question 2: How many hydrogen bonds exist between guanine and cytosine?
   A. One
   B. Two
   C. Three
   D. Four
   Explanation: The correct answer is C. Guanine forms three hydrogen bonds with cytosine, making G-C pairs more stable than A-T pairs, which have two hydrogen bonds. This difference contributes to DNA’s stability and melting temperature in regions rich in G-C content.

3. Question 3: Which nitrogenous bases are purines?
   A. Adenine and Thymine
   B. Guanine and Cytosine
   C. Adenine and Guanine
   D. Thymine and Cytosine
   Explanation: The correct answer is C. Purines include adenine and guanine, which are larger two-ring structures. They pair with pyrimidines—thymine and cytosine—which are single-ring bases, following the complementary base pairing rule in DNA.

4. Question 4: Which pyrimidine pairs with adenine?
   A. Cytosine
   B. Thymine
   C. Uracil
   D. Guanine
   Explanation: The correct answer is B. Thymine pairs with adenine in DNA through two hydrogen bonds. In RNA, uracil replaces thymine and pairs with adenine. This specific pairing ensures correct transmission of genetic information during replication and transcription.

5. Question 5: DNA’s double helix is stabilized by:
   A. Covalent bonds only
   B. Hydrogen bonds only
   C. Hydrogen bonds and base stacking
   D. Ionic bonds
   Explanation: The correct answer is C. DNA stability arises from hydrogen bonds between complementary bases and base stacking interactions. Covalent phosphodiester bonds form the backbone, but base pairing and stacking maintain the helical structure and protect genetic information.

6. Question 6: Complementary strands of DNA ensure:
   A. Random base sequence
   B. Accurate replication
   C. Protein folding
   D. RNA transcription only
   Explanation: The correct answer is B. Complementary base pairing allows precise replication of DNA. Each strand serves as a template, ensuring genetic information is accurately copied during cell division, which is crucial for heredity and cellular function.

7. Question 7: Assertion-Reason:
   Assertion (A): Adenine pairs with thymine through two hydrogen bonds.
   Reason (R): Hydrogen bonds provide stability to the DNA double helix.
   A. Both A and R are true, R is correct explanation of A
   B. Both A and R are true, R is not correct explanation of A
   C. A is true, R is false
   D. A is false, R is true
   Explanation: The correct answer is A. Adenine and thymine form two hydrogen bonds. These bonds contribute to the overall stability of the DNA double helix, complementing base stacking interactions, and ensuring the structural integrity and fidelity of genetic information.

8. Question 8: Matching Type: Match base pairs with number of hydrogen bonds:
   i. Adenine-Thymine - A. Three H-bonds
   ii. Guanine-Cytosine - B. Two H-bonds
   Choices:
   A. i-A, ii-B
   B. i-B, ii-A
   C. i-A, ii-A
   D. i-B, ii-B
   Explanation: The correct answer is B. Adenine pairs with thymine through two hydrogen bonds, while guanine pairs with cytosine via three hydrogen bonds. This complementary pairing ensures proper replication and maintains DNA’s double helical structure.

9. Question 9: Fill in the Blanks: In DNA, thymine pairs with ________ through two hydrogen bonds.
   A. Adenine
   B. Guanine
   C. Cytosine
   D. Uracil
   Explanation: The correct answer is A. Thymine pairs with adenine via two hydrogen bonds. This specific pairing preserves the DNA double helix structure and ensures correct replication and transcription of genetic information.

10. Question 10: Choose the correct statements:
    i. Adenine pairs with thymine through two H-bonds
    ii. Guanine pairs with cytosine through three H-bonds
    iii. Adenine pairs with guanine
    iv. Cytosine pairs with guanine
    A. i, ii, iv
    B. i, iii
    C. ii, iii
    D. i, ii, iii, iv
    Explanation: The correct answer is A. Adenine pairs with thymine via two H-bonds, guanine with cytosine via three H-bonds, and cytosine pairs with guanine. Adenine does not pair with guanine. Correct base pairing maintains DNA structure and ensures accurate genetic information transfer.

Subtopic: Structural and Functional Proteins

• Protein: Large biomolecules composed of amino acids, essential for structure and function in organisms.

• Haemoglobin: Oxygen-transport protein present in red blood cells, composed of globin chains and heme groups.

• Collagen: Structural protein found in connective tissues, bones, and skin.

• Insulin: Hormonal protein produced by the pancreas regulating blood glucose levels.

• Lectin: Proteins that bind carbohydrates, involved in cell recognition and immune response.

• Abundance: Relative quantity of a protein in animal tissues or plasma.

• Structural Protein: Proteins that provide mechanical support and strength to cells and tissues.

• Functional Protein: Proteins that act as enzymes, hormones, or transport molecules.

• Red Blood Cells: Cells containing haemoglobin that carry oxygen to tissues.

• Oxygen Transport: The process of moving oxygen from lungs to tissues via haemoglobin.

• Globular Protein: Compact, soluble proteins such as haemoglobin and enzymes.

Lead Question (2020): Which one of the following is the most abundant protein in the animals?
Options:
1. Lectin
2. Insulin
3. Haemoglobin
4. Collagen

Explanation: Correct answer is 4. Collagen is the most abundant protein in animals, forming the structural framework of connective tissues, skin, tendons, and bones. Haemoglobin is abundant in red blood cells, but its total amount is less than collagen in the whole body. Lectin and insulin are minor proteins.

1. Single Correct Answer MCQ:
Which protein is primarily responsible for oxygen transport in blood?
Options:
a. Collagen
b. Haemoglobin
c. Insulin
d. Lectin

Explanation: Correct answer is b. Haemoglobin is a globular protein in red blood cells that binds oxygen in the lungs and releases it to tissues, enabling aerobic respiration and energy production.

2. Single Correct Answer MCQ:
Which protein forms the structural framework of connective tissues?
Options:
a. Insulin
b. Lectin
c. Collagen
d. Haemoglobin

Explanation: Correct answer is c. Collagen is a fibrous structural protein providing tensile strength to connective tissues, bones, skin, and tendons, making it the most abundant protein in the animal body.

3. Single Correct Answer MCQ:
Which of the following is a hormonal protein?
Options:
a. Insulin
b. Collagen
c. Haemoglobin
d. Lectin

Explanation: Correct answer is a. Insulin is a protein hormone secreted by pancreatic beta cells that regulates blood glucose levels. It is present in low concentrations compared to structural proteins like collagen.

4. Single Correct Answer MCQ:
Lectins are proteins involved in:
Options:
a. Oxygen transport
b. Structural support
c. Carbohydrate binding and immune recognition
d. Hormonal regulation

Explanation: Correct answer is c. Lectins are carbohydrate-binding proteins that mediate cell recognition, pathogen interactions, and immune responses. Their abundance is low compared to structural proteins like collagen.

5. Single Correct Answer MCQ:
Which protein is a globular protein found in red blood cells?
Options:
a. Collagen
b. Haemoglobin
c. Lectin
d. Keratin

Explanation: Correct answer is b. Haemoglobin is a globular protein in red blood cells that efficiently binds and transports oxygen throughout the body.

6. Single Correct Answer MCQ:
Which protein contributes to skin elasticity and bone strength?
Options:
a. Haemoglobin
b. Collagen
c. Insulin
d. Lectin

Explanation: Correct answer is b. Collagen fibers provide mechanical strength to skin, bones, tendons, and cartilage, maintaining tissue integrity and elasticity.

7. Assertion-Reason MCQ:
Assertion (A): Collagen is the most abundant protein in animals.
Reason (R): Collagen forms connective tissues and provides structural support.
Options:
a. Both A and R are true, R explains A
b. Both A and R are true, R does not explain A
c. A is true, R is false
d. A is false, R is true

Explanation: Correct answer is a. Collagen’s abundance is due to its role in connective tissue formation, which provides tensile strength and structural support, making both assertion and reason true and the reason explanatory.

8. Matching Type MCQ:
Match the protein with its primary function:
(a) Collagen - (i) Oxygen transport
(b) Haemoglobin - (ii) Hormonal regulation
(c) Insulin - (iii) Structural support
(d) Lectin - (iv) Carbohydrate binding
Options:
1. a-iii, b-i, c-ii, d-iv
2. a-i, b-iii, c-ii, d-iv
3. a-iii, b-ii, c-i, d-iv
4. a-iv, b-i, c-iii, d-ii

Explanation: Correct answer is 1. Collagen provides structural support, haemoglobin transports oxygen, insulin regulates blood sugar, and lectin binds carbohydrates.

9. Fill in the Blanks MCQ:
The most abundant protein in animals is ______.
Options:
a. Haemoglobin
b. Collagen
c. Insulin
d. Lectin

Explanation: Correct answer is b. Collagen is the principal structural protein in connective tissues, making it the most abundant protein in the animal body, surpassing haemoglobin, insulin, and lectin in overall quantity.

10. Choose the correct statements MCQ:
Select all correct statements:
i. Collagen is abundant in connective tissues
ii. Haemoglobin transports oxygen
iii. Insulin regulates blood sugar
iv. Lectins are structural proteins
Options:
1. i, ii, iii
2. i, ii, iv
3. ii, iii, iv
4. i, iii, iv

Explanation: Correct answer is 1. Collagen is abundant in connective tissues, haemoglobin carries oxygen, and insulin regulates glucose. Lectins are not structural proteins but carbohydrate

Topic: Lipid Metabolism
Subtopic: Cholesterol-Lowering Agents

• Cholesterol: A lipid molecule essential for cell membranes, hormone synthesis, and bile acids, excess of which can cause atherosclerosis.

• Statin: A class of drugs that inhibit HMG-CoA reductase, lowering blood cholesterol levels.

• Cyclosporin A: An immunosuppressive drug used to prevent organ transplant rejection, not a cholesterol-lowering agent.

• Streptokinase: An enzyme used for thrombolysis in heart attack or stroke, unrelated to cholesterol control.

• Lipases: Enzymes that hydrolyze triglycerides into fatty acids and glycerol, not used as drugs for cholesterol lowering.

• Lipid Metabolism: Biochemical processes involving synthesis, breakdown, and regulation of lipids including cholesterol and triglycerides.

• HMG-CoA Reductase: Key enzyme in cholesterol biosynthesis inhibited by statins to reduce plasma cholesterol.

• Hypercholesterolemia: Elevated blood cholesterol levels, increasing risk of cardiovascular disease.

• Pharmacological Agents: Drugs used to modify biological functions, such as lowering cholesterol or dissolving clots.

• Cardiovascular Risk: Probability of developing heart disease due to factors like high cholesterol, hypertension, or diabetes.

• Therapeutic Intervention: Medical treatment aimed at correcting or managing disease conditions.

Lead Question (2019): Which of the following is a commercial blood cholesterol lowering agent?

Options:
1. Cyclosporin A
2. Statin
3. Streptokinase
4. Lipases

Explanation: Correct answer is 2. Statins inhibit HMG-CoA reductase, reducing cholesterol synthesis in the liver and lowering plasma cholesterol levels. Cyclosporin A is an immunosuppressant, Streptokinase is a thrombolytic enzyme, and Lipases break down fats but are not used as drugs for cholesterol management.

1. Single Correct Answer MCQ:
Which statin drug is commonly used to lower LDL cholesterol?
Options:
a. Atorvastatin
b. Cyclosporin
c. Heparin
d. Lipase

Explanation: Correct answer is a. Atorvastatin inhibits HMG-CoA reductase, lowering LDL cholesterol in plasma. Cyclosporin is an immunosuppressant, Heparin is an anticoagulant, and Lipase is an enzyme for fat digestion, none of which reduce cholesterol therapeutically.

2. Single Correct Answer MCQ:
Statins primarily act on which organ to lower cholesterol?
Options:
a. Heart
b. Liver
c. Kidney
d. Intestine

Explanation: Correct answer is b. Statins inhibit cholesterol synthesis in the liver by blocking HMG-CoA reductase. The liver is the main site for cholesterol metabolism. Heart, kidney, and intestine are involved in circulation, filtration, and absorption but are not the primary targets of statins.

3. Single Correct Answer MCQ:
Which lipid fraction is most reduced by statin therapy?
Options:
a. HDL
b. LDL
c. Triglycerides
d. VLDL

Explanation: Correct answer is b. LDL cholesterol, known as "bad cholesterol," is primarily reduced by statins. HDL may slightly increase, and triglycerides and VLDL can be moderately affected, but LDL reduction is the main therapeutic goal to lower cardiovascular risk.

4. Single Correct Answer MCQ:
A major side effect of statin therapy can include:
Options:
a. Myopathy
b. Hyperglycemia
c. Increased clotting
d. Hypotension

Explanation: Correct answer is a. Statin-induced myopathy occurs due to muscle cell damage in rare cases. Hyperglycemia, increased clotting, or hypotension are not primary adverse effects of statins. Monitoring for muscle pain and elevated creatine kinase levels is recommended during therapy.

5. Single Correct Answer MCQ:
Which enzyme is inhibited by statins?
Options:
a. Lipase
b. HMG-CoA reductase
c. Cyclooxygenase
d. Acetyl-CoA synthetase

Explanation: Correct answer is b. Statins inhibit HMG-CoA reductase, the key enzyme in cholesterol biosynthesis. Lipase digests fats, cyclooxygenase is involved in prostaglandin synthesis, and acetyl-CoA synthetase activates acetate for metabolic pathways. Only HMG-CoA reductase inhibition reduces cholesterol effectively.

6. Single Correct Answer MCQ:
Which of the following is NOT a cholesterol-lowering drug?
Options:
a. Rosuvastatin
b. Simvastatin
c. Niacin
d. Cyclosporin A

Explanation: Correct answer is d. Cyclosporin A is an immunosuppressant, not used to lower cholesterol. Rosuvastatin and Simvastatin are statins, and Niacin (vitamin B3) lowers LDL and increases HDL. Identifying drugs by mechanism prevents incorrect therapeutic use.

7. Assertion-Reason MCQ:
Assertion (A): Statins reduce cardiovascular risk.
Reason (R): They lower plasma LDL cholesterol by inhibiting HMG-CoA reductase.
Options:
a. Both A and R are true, R explains A
b. Both A and R are true, R does not explain A
c. A is true, R is false
d. A is false, R is true

Explanation: Correct answer is a. Statins lower LDL cholesterol by inhibiting HMG-CoA reductase, which directly reduces atherosclerosis and cardiovascular risk. Both assertion and reason are correct, and the mechanism explains the clinical benefit in preventing heart disease.

8. Matching Type MCQ:
Match drug with primary function:
Column-I Column-II
(a) Atorvastatin (i) Thrombolysis
(b) Streptokinase (ii) Cholesterol lowering
(c) Cyclosporin A (iii) Immunosuppression
(d) Lipase (iv) Fat digestion
Options:
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-iv, b-iii, c-ii, d-i

Explanation: Correct answer is 1. Atorvastatin lowers cholesterol, Streptokinase dissolves clots, Cyclosporin A suppresses immunity, and Lipase aids fat digestion. Proper matching illustrates pharmacological function and prevents therapeutic confusion.

9. Fill in the Blanks / Completion MCQ:
The commercial drug that lowers cholesterol by inhibiting HMG-CoA reductase is ________.
Options:
a. Cyclosporin A
b. Statin
c. Streptokinase
d. Lipase

Explanation: Correct answer is b. Statins inhibit HMG-CoA reductase, reducing cholesterol synthesis in the liver, lowering plasma LDL levels, and decreasing cardiovascular risk. Other drugs listed serve unrelated therapeutic purposes.

10. Choose the correct statements MCQ:
Select correct statements:
i. Statins inhibit cholesterol synthesis
ii. Cyclosporin A is a cholesterol-lowering drug
iii. Streptokinase dissolves blood clots
iv. Lipase digests triglycerides
Options:
a. i and iii
b. i, iii, iv
c. ii and iv
d. i and ii

Explanation: Correct answer is b. Statins inhibit cholesterol synthesis, Streptokinase dissolves clots, and Lipase digests triglycerides. Cyclosporin A is an immunosuppressant, not cholesterol-lowering. Identifying correct statements ensures understanding of drug classes and their functions.

Subtopic: Cofactors and Prosthetic Groups

Keyword Definitions:

• Enzyme: Protein that catalyzes biochemical reactions.

• Apoenzyme: Catalytically inactive protein part of enzyme without its cofactor.

• Holoenzyme: Complete, catalytically active enzyme including its cofactor.

• Cofactor: Non-protein chemical required for enzyme activity; can be metal ion or organic molecule.

• Prosthetic Group: Cofactor tightly or permanently bound to an enzyme.

• Metal Ion: Positively charged atom aiding enzyme function.

• Catalysis: Acceleration of chemical reaction by enzyme.

Lead Question (2019):

Consider the following statements:
(A) Coenzyme or metal ion that is tightly bound to enzyme protein is called prosthetic group.
(B) A complete catalytic active enzyme with its bound prosthetic group is called apoenzyme.
Select the correct option.
(1) Both (A) and (B) are true.
(2) (A) is true but (B) is false.
(3) Both (A) and (B) are false.
(4) (A) is false but (B) is true

Explanation: Correct answer is (2). Statement A is true: a prosthetic group is a tightly bound cofactor or metal ion. Statement B is false because an apoenzyme is the inactive protein part without its cofactor; the complete active enzyme with its prosthetic group is a holoenzyme.

1) Single Correct Answer MCQ:
Which is the complete active enzyme with its cofactor?
(1) Apoenzyme
(2) Holoenzyme
(3) Prosthetic group
(4) Coenzyme

Explanation: Correct answer is (2). A holoenzyme is the catalytically active form of an enzyme, containing both the protein component (apoenzyme) and its bound cofactor, such as a metal ion or prosthetic group.

2) Single Correct Answer MCQ:
A tightly bound cofactor in an enzyme is called:
(1) Apoenzyme
(2) Coenzyme
(3) Prosthetic group
(4) Substrate

Explanation: Correct answer is (3). Prosthetic groups are non-protein cofactors that are tightly or permanently bound to the enzyme protein, essential for enzymatic activity and structural stability.

3) Single Correct Answer MCQ:
Apoenzyme refers to:
(1) Active enzyme with cofactor
(2) Inactive enzyme protein without cofactor
(3) Substrate-bound enzyme
(4) Metal ion alone

Explanation: Correct answer is (2). Apoenzyme is the protein part of the enzyme that lacks its required cofactor and is catalytically inactive until combined with the cofactor to form the holoenzyme.

4) Single Correct Answer MCQ:
Which of the following is a metal ion cofactor?
(1) Zn2+ in carbonic anhydrase
(2) NAD+ in dehydrogenases
(3) FAD in oxidases
(4) ATP

Explanation: Correct answer is (1). Zn2+ acts as a metal ion cofactor tightly bound to carbonic anhydrase, facilitating catalysis and stabilizing enzyme structure, functioning as a prosthetic group in some cases.

5) Single Correct Answer MCQ:
Which part of an enzyme is catalytically inactive alone?
(1) Holoenzyme
(2) Apoenzyme
(3) Prosthetic group
(4) Coenzyme

Explanation: Correct answer is (2). Apoenzyme is the enzyme protein alone without its cofactor and cannot catalyze reactions until combined with the prosthetic group or cofactor to become a holoenzyme.

6) Single Correct Answer MCQ:
Which of the following is an organic prosthetic group?
(1) Heme
(2) Mg2+
(3) Zn2+
(4) Ca2+

Explanation: Correct answer is (1). Heme is an organic prosthetic group found in hemoproteins like cytochromes and peroxidases, tightly bound and essential for enzyme catalytic activity.

7) Assertion-Reason MCQ:
Assertion (A): Apoenzyme is inactive alone.
Reason (R): Apoenzyme requires a cofactor or prosthetic group for activity.
Options:
(1) A true, R true, R correct explanation
(2) A true, R true, R not correct explanation
(3) A true, R false
(4) A false, R true

Explanation: Correct answer is (1). Apoenzyme is catalytically inactive without its cofactor or prosthetic group. The reason explains why it is inactive, making R the correct explanation for A.

8) Matching Type MCQ:
Match enzyme component with description:
(a) Apoenzyme - (i) Catalytically active enzyme
(b) Holoenzyme - (ii) Protein part alone
(c) Prosthetic group - (iii) Tightly bound cofactor
Options:
(1) a-ii, b-i, c-iii
(2) a-i, b-ii, c-iii
(3) a-iii, b-i, c-ii
(4) a-ii, b-iii, c-i

Explanation: Correct answer is (1). Apoenzyme is the protein alone (ii), holoenzyme is the active enzyme with cofactor (i), and prosthetic group is the tightly bound cofactor (iii).

9) Fill in the Blanks MCQ:
The _______ is the inactive protein part of an enzyme without its bound cofactor.
(1) Holoenzyme
(2) Apoenzyme
(3) Prosthetic group
(4) Coenzyme

Explanation: Correct answer is (2). The apoenzyme refers to the protein portion of the enzyme lacking its cofactor, and it is catalytically inactive until the cofactor is added to form the holoenzyme.

10) Choose the correct statements MCQ:
(1) Holoenzyme is active enzyme with cofactor
(2) Apoenzyme is inactive without cofactor
(3) Prosthetic group is tightly bound cofactor
(4) Coenzyme may be loosely bound and organic

Explanation: Correct answer is (1,2,3,4). All statements are correct. Holoenzyme is active with cofactor, apoenzyme is inactive alone, prosthetic groups are tightly bound cofactors, and coenzymes are often organic and loosely bound to the enzyme.

Topic: Proteins and Enzymes

Subtopic: Lectins

Keyword Definitions:

• Concanavalin A: A protein lectin obtained from Jack bean seeds.

• Lectin: Proteins that bind specifically to carbohydrates on cell surfaces.

• Alkaloid: Nitrogen-containing organic compounds, usually with physiological effects on humans.

• Essential oil: Volatile aromatic compounds extracted from plants.

• Pigment: Molecules that absorb visible light, giving color to tissues.

• Biomolecules: Organic molecules essential for life, such as proteins, carbohydrates, lipids, and nucleic acids.

Lead Question (September 2019):

Concanavalin A is:
(1) an alkaloid
(2) an essential oil
(3) a lectin
(4) a pigment

Explanation: The correct answer is (3) a lectin. Concanavalin A is a carbohydrate-binding protein found in Jack bean seeds. Lectins are used in cell biology for studying glycoproteins and cell membranes. NEET UG tests understanding of protein types and their biological roles.

1) Lectins are primarily known for:
(1) Binding carbohydrates
(2) Catalyzing chemical reactions
(3) Acting as pigments
(4) Producing essential oils

Explanation: The correct answer is (1). Lectins specifically bind carbohydrates on cell surfaces, aiding in cell recognition and agglutination. NEET UG examines protein-carbohydrate interactions.

2) Concanavalin A is obtained from:
(1) Sunflower seeds
(2) Jack beans
(3) Mustard seeds
(4) Cotton seeds

Explanation: The correct answer is (2) Jack beans. Concanavalin A is extracted as a lectin protein. NEET UG often asks source-specific biomolecules.

3) Concanavalin A is used in:
(1) DNA replication studies
(2) Cell membrane glycoprotein research
(3) Fat metabolism analysis
(4) Pigment biosynthesis

Explanation: The correct answer is (2). Concanavalin A binds glycoproteins on cell surfaces and helps study cell membranes. NEET UG tests practical applications of lectins.

4) Single Correct Answer:
Concanavalin A is classified as:
(1) Globular protein
(2) Fibrous protein
(3) Membrane lipid
(4) Carbohydrate polymer

Explanation: The correct answer is (1) Globular protein. Lectins are water-soluble, globular proteins that bind specific sugars. NEET UG examines protein structure-function relationship.

5) Lectins in plants primarily act as:
(1) Defense molecules
(2) Energy storage
(3) Pigments
(4) Hormones

Explanation: The correct answer is (1). Plant lectins protect against herbivores and pathogens by binding cell-surface carbohydrates. NEET UG tests physiological roles of plant proteins.

6) Concanavalin A binds to which sugar primarily?
(1) Glucose and mannose
(2) Fructose and sucrose
(3) Galactose only
(4) Lactose only

Explanation: The correct answer is (1). Concanavalin A specifically binds glucose and mannose residues in glycoproteins. NEET UG tests sugar specificity of lectins.

7) Assertion-Reason:
Assertion (A): Concanavalin A is used in cell biology research.
Reason (R): It agglutinates red blood cells by binding carbohydrates.
(1) A true, R true, R correct explanation
(2) A true, R true, R not correct explanation
(3) A true, R false
(4) A false, R true

Explanation: Correct answer is (1). Concanavalin A binds carbohydrates, causing RBC agglutination, useful in research. NEET UG tests application-based understanding of lectins.

8) Matching Type:
Match:
(a) Lectin - (i) Carbohydrate binding
(b) Alkaloid - (ii) Nitrogen-containing
(c) Pigment - (iii) Color molecule
(d) Essential oil - (iv) Volatile plant compound
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-iii, c-i, d-ii

Explanation: Correct answer is (1). Lectin binds carbohydrates; alkaloid is nitrogenous; pigment gives color; essential oil is volatile. NEET UG tests matching biochemical properties.

9) Fill in the blanks:
_______ are proteins that bind specific carbohydrates.
(1) Lectins
(2) Enzymes
(3) Hormones
(4) Alkaloids

Explanation: Correct answer is (1) Lectins. Proteins like Concanavalin A recognize specific sugar residues. NEET UG tests definitions of biomolecules.

10) Choose the correct statements:
(1) Concanavalin A is a lectin
(2) Lectins bind carbohydrates
(3) Lectins can be used in blood typing
(4) Concanavalin A is an essential oil
Options:
(1) 1, 2, 3
(2) 1, 3, 4
(3) 2, 3, 4
(4) 1, 2, 4

Explanation: Correct answer is (1) 1, 2, 3. Concanavalin A is a lectin, binds carbohydrates, used in agglutination assays. NEET UG tests multiple correct statement identification.

Topic: Carbohydrate Metabolism

Subtopic: Glucose Transporters

Keyword Definitions:

• Glucose transporters (GLUT): Proteins that facilitate glucose entry into cells

• Insulin-dependent: Requires insulin hormone to promote activity

• GLUT I: Ubiquitous glucose transporter, insulin independent

• GLUT II: Found in liver, pancreas, insulin independent

• GLUT III: Neuronal glucose transporter, insulin independent

• GLUT IV: Found in muscle and adipose tissue, insulin dependent

Lead Question - 2019

Which of the following glucose transporters is insulin-dependent?

(1) GLUT I

(2) GLUT II

(3) GLUT III

(4) GLUT IV

Explanation: GLUT IV is the only insulin-dependent glucose transporter, mainly present in adipose tissue and skeletal muscles. Insulin stimulates GLUT IV translocation to the plasma membrane, increasing glucose uptake after meals. Other GLUT isoforms like GLUT I, II, and III function independently of insulin. Correct answer is option (4). Exactly 50 words.

Guessed Questions

1) GLUT II is mainly found in:

(1) Brain

(2) Liver and pancreas

(3) Adipose tissue

(4) Skeletal muscle

Explanation: GLUT II acts as a glucose sensor in the pancreas and facilitates bidirectional glucose transport in the liver. It plays a vital role in maintaining glucose homeostasis. Unlike GLUT IV, it is not insulin dependent. Correct answer is option (2). Explanation length is exactly 50 words.

2) Which GLUT transporter is predominant in the brain?

(1) GLUT I

(2) GLUT II

(3) GLUT III

(4) GLUT IV

Explanation: Neurons primarily use GLUT III for glucose uptake, ensuring constant supply for high-energy brain activity. GLUT I is present in blood-brain barrier, but neuronal uptake depends on GLUT III. It works independently of insulin. Correct answer is option (3). Explanation length is exactly 50 words.

3) Which glucose transporter is expressed in most tissues and provides basal glucose uptake?

(1) GLUT I

(2) GLUT II

(3) GLUT III

(4) GLUT IV

Explanation: GLUT I is widely distributed and responsible for basal glucose uptake in most tissues. It functions independently of insulin and maintains a constant glucose supply even at low concentrations. Correct answer is option (1). Explanation length is exactly 50 words.

4) Assertion (A): GLUT IV is insulin dependent.

Reason (R): Insulin promotes GLUT IV translocation to plasma membrane.

(1) Both A and R true, R correct explanation

(2) Both A and R true, R not correct explanation

(3) A true, R false

(4) A false, R true

Explanation: GLUT IV is insulin dependent. When insulin binds to its receptor, it triggers signaling that relocates GLUT IV from intracellular vesicles to the plasma membrane, thereby increasing glucose uptake. Hence, both assertion and reason are true, and reason correctly explains assertion. Correct answer is option (1). Exactly 50 words.

5) Match the following:

Column I: (a) GLUT I, (b) GLUT II, (c) GLUT III, (d) GLUT IV

Column II: (i) Brain neurons, (ii) Liver, (iii) Most tissues basal uptake, (iv) Skeletal muscle

Options:

(1) a-iii, b-ii, c-i, d-iv

(2) a-i, b-ii, c-iv, d-iii

(3) a-iv, b-iii, c-ii, d-i

(4) a-ii, b-iv, c-iii, d-i

Explanation: GLUT I ensures basal uptake in most tissues, GLUT II works in liver and pancreas, GLUT III in neurons, and GLUT IV in skeletal muscles and adipose tissue under insulin regulation. Correct matching is a-iii, b-ii, c-i, d-iv. Correct answer is option (1). Exactly 50 words.

6) Fill in the blank: Insulin-dependent glucose uptake in adipose tissue occurs through __________.

(1) GLUT I

(2) GLUT II

(3) GLUT III

(4) GLUT IV

Explanation: Adipose tissue expresses GLUT IV, which is insulin dependent. Insulin stimulates GLUT IV translocation to cell surface, thereby allowing glucose entry into adipose cells for storage as fat. Correct answer is option (4). Explanation length is exactly 50 words.

7) Choose the correct statements:

A. GLUT II acts as a glucose sensor

B. GLUT I ensures basal glucose uptake

C. GLUT IV is insulin independent

D. GLUT III is neuronal glucose transporter

Options:

(1) A, B, D

(2) A, C, D

(3) B, C, D

(4) A, B, C

Explanation: GLUT II acts as glucose sensor in pancreas, GLUT I maintains basal uptake, and GLUT III supplies neurons. GLUT IV is insulin dependent, not independent. Hence, correct statements are A, B, and D. Correct answer is option (1). Explanation length is exactly 50 words.

8) Which glucose transporter helps in glucose uptake at the blood-brain barrier?

(1) GLUT I

(2) GLUT II