Subtopic: Nitrogenous Waste and Terrestrial Adaptations
Keyword Definitions:
Nitrogenous Wastes: Metabolic waste products formed from the breakdown of proteins and nucleic acids, primarily ammonia, urea, and uric acid.
Ammonotelic: Animals that excrete nitrogen mainly as ammonia, highly toxic and soluble in water.
Ureotelic: Animals that excrete nitrogen primarily as urea, less toxic and water-soluble.
Uricotelic: Animals that excrete nitrogen as uric acid, low toxicity and conserves water.
Terrestrial Adaptations: Physiological modifications enabling animals to survive in land environments with limited water availability.
Lead Question – 2022 (Abroad)
Terrestrial adaptations necessitated the production of:
1. Highly toxic nitrogenous wastes like urea and uric acid
2. Lesser toxic nitrogenous wastes like urea and uric acid
3. Lesser toxic nitrogenous wastes like ammonia and urea
4. Highly toxic nitrogenous wastes like ammonia and urea
Explanation:
The correct answer is Lesser toxic nitrogenous wastes like urea and uric acid. Terrestrial animals must conserve water while excreting nitrogenous wastes. Ammonia is highly toxic and requires large water volumes for excretion, unsuitable for land habitats. Urea and uric acid are less toxic and can be excreted with minimal water loss. Ureotelic and uricotelic excretion systems represent evolutionary adaptations to terrestrial life, enabling efficient nitrogen elimination without causing toxicity, dehydration, or disturbance in electrolyte balance. These adaptations are crucial for survival in arid and semi-arid environments.
1. Which of the following excretes nitrogen primarily as uric acid?
1. Frog
2. Lizard
3. Fish
4. Amphibian
Explanation: The correct answer is Lizard. Lizards are terrestrial and uricotelic, excreting nitrogen as uric acid, conserving water. Frogs and amphibians excrete mostly ammonia or urea, requiring more water. Fish are ammonotelic. Uricotelic excretion minimizes water loss and toxicity, an essential adaptation for land-dwelling species, maintaining osmotic and nitrogen balance efficiently.
2. Ammonia is highly toxic because:
1. It is insoluble in water
2. It reacts with urea
3. It disrupts acid-base balance and requires dilution
4. It is less soluble
Explanation: Ammonia is highly toxic due to its ability to disturb acid-base balance and nerve function. Ammonotelic animals require large volumes of water to dilute ammonia for excretion. Terrestrial adaptations favor urea or uric acid production, which are less toxic and water-efficient. This explains why land-dwelling animals produce urea or uric acid instead of ammonia.
3. Ureotelic animals primarily excrete nitrogen as:
1. Ammonia
2. Urea
3. Uric acid
4. Nitrate
Explanation: The correct answer is Urea. Ureotelic animals convert ammonia into urea in the liver. Urea is less toxic, water-soluble, and can be excreted with minimal water loss. This adaptation allows terrestrial animals like mammals to conserve water while efficiently eliminating nitrogen, avoiding the high toxicity associated with direct ammonia excretion.
4. Which excretory adaptation minimizes water loss in birds?
1. Ammonotelic
2. Ureotelic
3. Uricotelic
4. Nephrotoxic
Explanation: Uricotelic excretion, as in birds, produces uric acid, a white paste, conserving water. Unlike ammonia or urea, uric acid requires minimal water for excretion. This adaptation enables survival in arid habitats, allowing birds to maintain water balance while effectively eliminating nitrogenous wastes from protein metabolism.
5. Which organ primarily converts ammonia into urea in mammals?
1. Kidney
2. Liver
3. Heart
4. Spleen
Explanation: The correct answer is Liver. In mammals, the liver converts toxic ammonia into less toxic urea via the urea cycle. This process reduces toxicity, conserves water, and facilitates safe nitrogen excretion. Kidneys then excrete urea in urine. This is a key adaptation for terrestrial life.
6. Which nitrogenous waste is most soluble in water?
1. Urea
2. Uric acid
3. Ammonia
4. Creatinine
Explanation: Ammonia is highly soluble in water, facilitating rapid excretion in aquatic animals. Terrestrial animals convert ammonia to urea or uric acid, which are less toxic and can be excreted with minimal water, conserving water for survival on land. Solubility alone is insufficient; toxicity and water availability are critical.
7. Assertion-Reason Type:
Assertion (A): Terrestrial animals excrete urea or uric acid instead of ammonia.
Reason (R): Ammonia is highly toxic and requires large volumes of water for excretion.
1. Both A and R are true, and R is the correct explanation of A
2. Both A and R are true, but R is not the correct explanation of A
3. A is true, but R is false
4. A is false, but R is true
Explanation: Correct answer is option 1. Terrestrial adaptations favor production of urea or uric acid to conserve water and reduce toxicity. Ammonia is unsuitable due to high toxicity and the large water volume required for safe excretion, making ureotelism and uricotelism critical evolutionary adaptations for land-dwelling animals.
8. Matching Type:
Match the animal with its excretory product:
A. Frog – (i) Uric acid
B. Lizard – (ii) Urea
C. Fish – (iii) Ammonia
D. Mammal – (iv) Urea
1. A–ii, B–i, C–iii, D–iv
2. A–iii, B–i, C–iii, D–iv
3. A–iv, B–ii, C–iii, D–i
4. A–iii, B–ii, C–i, D–iv
Explanation: Correct answer is option 2. Frogs (amphibians) excrete ammonia in water, lizards produce uric acid, fish excrete ammonia, and mammals excrete urea. These adaptations reflect habitat-specific nitrogen excretion strategies to balance toxicity, water conservation, and survival in terrestrial versus aquatic environments.
9. Fill in the Blanks:
Animals that excrete nitrogen as a white paste to conserve water are called ___________.
1. Ammonotelic
2. Ureotelic
3. Uricotelic
4. Nephrotoxic
Explanation: Correct answer is Uricotelic. Birds and many reptiles excrete nitrogen as uric acid, a white paste. This adaptation reduces water loss and prevents ammonia toxicity. Ureotelic mammals excrete urea, and ammonotelic aquatic animals excrete ammonia directly, demonstrating habitat-driven evolutionary adaptation in nitrogen metabolism.
10. Choose the Correct Statements:
Statement I: Terrestrial adaptations favor production of urea and uric acid.
Statement II: Ammonia is the preferred nitrogenous waste in land animals.
1. Statement I is correct, Statement II is incorrect
2. Both statements are correct
3. Statement I is incorrect, Statement II is correct
4. Both statements are incorrect
Explanation: Correct answer is option 1. Terrestrial animals produce less toxic nitrogenous wastes like urea and
Topic: Nitrogenous Waste Elimination
Subtopic: Types of Excretion
Keyword Definitions:
• Nitrogenous Waste: Metabolic waste containing nitrogen produced from protein and nucleic acid metabolism.
• Excretion: Process of eliminating metabolic wastes from the body.
• Uricotelic: Organisms excreting nitrogen mainly as uric acid.
• Ureotelic: Organisms excreting nitrogen mainly as urea.
• Ammonotelic: Organisms excreting nitrogen mainly as ammonia.
• Pellet or Paste: Solid or semi-solid excretory product, typical of uric acid excretion.
• Salamandra: Genus of amphibians; some species excrete uric acid as paste.
• Hippocampus: Genus of seahorses.
• Pavo: Genus of peafowl.
• Ornithorhynchus: Genus of platypus.
Lead Question (2022):
Nitrogenous waste is excreted in the form of pellet or paste by:
(1) Salamandra
(2) Hippocampus
(3) Pavo
(4) Ornithorhynchus
Explanation: The correct answer is (3). Pavo, the peafowl, being a bird, is uricotelic and excretes nitrogenous waste as semi-solid uric acid in the form of pellets or paste. This adaptation reduces water loss and conserves water, which is essential for terrestrial birds living in varied habitats.
Guessed MCQs:
1. Single Correct Answer:
Which type of nitrogenous waste is excreted by birds?
(a) Uric acid
(b) Urea
(c) Ammonia
(d) Creatinine
Explanation: The correct answer is (a). Birds are uricotelic, excreting nitrogenous waste mainly as uric acid in a semi-solid form, which minimizes water loss and allows survival in terrestrial habitats with limited water availability.
2. Single Correct Answer:
Which organism is ureotelic, excreting nitrogen primarily as urea?
(a) Frog
(b) Pavo
(c) Salamandra
(d) Hippocampus
Explanation: The correct answer is (c). Salamandra, an amphibian, excretes nitrogenous waste mainly as urea dissolved in water, classifying it as ureotelic. Ureotelic excretion is common in terrestrial amphibians to conserve nitrogen and regulate osmotic balance.
3. Assertion-Reason MCQ:
Assertion (A): Birds excrete nitrogenous waste as pellets.
Reason (R): Uric acid is insoluble in water and conserves water in terrestrial environments.
(a) Both A and R are correct and R explains A
(b) Both A and R are correct but R does not explain A
(c) A is correct, R is false
(d) A is false, R is true
Explanation: The correct answer is (a). Birds like Pavo excrete nitrogen as uric acid pellets. Insolubility of uric acid ensures minimal water loss, an adaptation for terrestrial life, making the reason correctly explain the assertion.
4. Matching Type MCQ:
Match the organism with its nitrogenous excretion type:
A. Pavo – (i) Uricotelic
B. Salamandra – (ii) Ureotelic
C. Hippocampus – (iii) Ammonotelic
D. Ornithorhynchus – (iv) Ureotelic
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–iii, C–ii, D–iv
Explanation: The correct answer is (1). Pavo excretes uric acid (uricotelic), Salamandra excretes urea (ureotelic), Hippocampus excretes ammonia (ammonotelic), and Ornithorhynchus excretes urea (ureotelic), reflecting adaptations to water availability and habitat.
5. Single Correct Answer:
Which nitrogenous waste form minimizes water loss?
(a) Uric acid
(b) Urea
(c) Ammonia
(d) Creatinine
Explanation: The correct answer is (a). Uric acid is insoluble and excreted as a semi-solid paste or pellet, which reduces water loss. Birds and many reptiles use this form to survive in terrestrial habitats with limited water availability.
6. Single Correct Answer:
Which organism is ammonotelic?
(a) Hippocampus
(b) Pavo
(c) Salamandra
(d) Ornithorhynchus
Explanation: The correct answer is (a). Hippocampus, a marine fish, excretes nitrogen primarily as ammonia directly into surrounding water. Ammonotelic excretion is common in aquatic animals where water is abundant for dilution.
7. Fill in the Blanks:
Excretion of nitrogenous waste as ________ helps birds conserve water.
(a) pellets
(b) urea
(c) ammonia
(d) sweat
Explanation: The correct answer is (a). Birds excrete nitrogenous waste as pellets of uric acid, a semi-solid form, which reduces water loss and is an adaptation for terrestrial environments with limited water.
8. Single Correct Answer:
Which nitrogenous waste is soluble in water and excreted by amphibians?
(a) Urea
(b) Uric acid
(c) Ammonia
(d) Creatinine
Explanation: The correct answer is (a). Amphibians like Salamandra are ureotelic and excrete urea, a water-soluble nitrogenous waste, which facilitates excretion in moist environments while maintaining nitrogen balance.
9. Single Correct Answer:
Which adaptation allows birds to live in dry terrestrial habitats?
(a) Excretion of uric acid as paste
(b) Excretion of urea
(c) Excretion of ammonia
(d) Storing nitrogen in liver
Explanation: The correct answer is (a). Birds excrete nitrogen as insoluble uric acid pellets, which reduces water loss significantly. This adaptation supports survival in terrestrial and arid habitats.
10. Choose the correct statements:
(a) Birds are uricotelic.
(b) Amphibians like Salamandra are ureotelic.
(c) Marine fish excrete ammonia (ammonotelic).
(d) Pavo excretes urea in liquid form.
Options:
1. a, b, c only
2. a and d only
3. b and d only
4. All statements
Explanation: The correct answer is (1). Birds excrete uric acid (uricotelic), Salamandra excretes urea (ureotelic), and marine fish excrete ammonia (ammonotelic). Statement (d) is incorrect because Pavo excretes nitrogenous waste as uric acid pellets, not urea.
Topic: Regulation of Kidney Function
Subtopic: Renin-Angiotensin and ANF Mechanisms
Keyword Definitions:
Atrial Natriuretic Factor (ANF): A hormone secreted by atrial walls that lowers blood pressure by promoting sodium excretion.
Angiotensin II: A peptide hormone acting as a potent vasoconstrictor that increases blood pressure.
Vasa recta: Capillaries around Henle’s loop showing counter current exchange to maintain medullary gradient.
JG cells: Juxtaglomerular cells releasing renin during low blood pressure or GFR reduction.
Renin: An enzyme initiating the renin-angiotensin system, ultimately raising blood pressure.
Glomerular Filtration Rate (GFR): Volume of filtrate formed per minute in glomeruli, crucial for kidney function.
Lead Question - 2020 (COVID Reexam)
Select the correct statement:
1. Atrial Natriuretic Factor increases the blood pressure.
2. Angiotensin II is a powerful vasodilator.
3. Counter current pattern of blood flow is not observed in vasa recta.
4. Reduction in Glomerular Filtration Rate activates JG cells to release renin.
Explanation: ANF lowers blood pressure, not increases. Angiotensin II is a vasoconstrictor, not vasodilator. Vasa recta exhibits counter current flow, not absent. Reduced GFR stimulates juxtaglomerular cells to release renin, restoring pressure. Correct answer is option 4, reduction in GFR activates JG cells to release renin.
1. Which enzyme is secreted by juxtaglomerular cells?
a) Renin
b) Trypsin
c) Pepsin
d) Lipase
Explanation: Juxtaglomerular cells secrete renin when blood pressure or GFR falls. Renin converts angiotensinogen to angiotensin I, initiating the renin-angiotensin-aldosterone system. Correct answer is option a, renin.
2. ANF promotes which physiological effect?
a) Sodium retention
b) Sodium excretion
c) Vasoconstriction
d) Increase in renin release
Explanation: ANF, secreted by atrial walls due to high blood volume, promotes sodium and water excretion, lowering blood pressure. It acts as a vasodilator and antagonizes the renin-angiotensin system. Correct answer is option b, sodium excretion.
3. Angiotensin II acts as:
a) Vasodilator
b) Vasoconstrictor
c) Anticoagulant
d) Antidiuretic
Explanation: Angiotensin II is a powerful vasoconstrictor that raises blood pressure. It also stimulates aldosterone secretion, enhancing sodium reabsorption in the kidney. Correct answer is option b, vasoconstrictor.
4. Which hormone directly increases sodium reabsorption in kidneys?
a) Aldosterone
b) ADH
c) Renin
d) ANF
Explanation: Aldosterone acts on distal convoluted tubule and collecting duct to enhance sodium reabsorption and potassium secretion. This increases water retention and blood pressure. Correct answer is option a, aldosterone.
5. Which structure senses a drop in blood pressure?
a) Afferent arteriole JG cells
b) Collecting duct cells
c) PCT brush border
d) Glomerular podocytes
Explanation: Juxtaglomerular (JG) cells of the afferent arteriole act as baroreceptors. They release renin when blood pressure falls. Correct answer is option a, afferent arteriole JG cells.
6. Counter current pattern in vasa recta serves to:
a) Maintain medullary osmotic gradient
b) Neutralize sodium ions
c) Increase GFR
d) Promote renin release
Explanation: Counter current exchange in vasa recta maintains the osmotic gradient created by Henle’s loop, ensuring water reabsorption and concentrated urine formation. Correct answer is option a, maintain medullary osmotic gradient.
7. Assertion (A): ANF decreases blood pressure.
Reason (R): ANF increases sodium reabsorption in kidney tubules.
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: ANF decreases blood pressure by promoting sodium excretion, not reabsorption. Hence, assertion is true but reason is false. Correct answer is option c, A true and R false.
8. Match the following:
A. ANF — i) Lowers blood pressure
B. Angiotensin II — ii) Raises blood pressure
C. Renin — iii) Converts angiotensinogen
D. Aldosterone — iv) Enhances sodium reabsorption
a) A-i, B-ii, C-iii, D-iv
b) A-ii, B-i, C-iv, D-iii
c) A-iii, B-iv, C-i, D-ii
d) A-iv, B-iii, C-ii, D-i
Explanation: ANF lowers blood pressure, angiotensin II raises blood pressure, renin converts angiotensinogen to angiotensin I, and aldosterone enhances sodium reabsorption. Correct answer is option a.
9. Fill in the blank: Reduction in blood pressure activates __________ cells to release renin.
a) Podocyte
b) Juxtaglomerular
c) Macula densa
d) Endothelial
Explanation: Juxtaglomerular (JG) cells sense reduced blood pressure or GFR and release renin, initiating the renin-angiotensin system to increase pressure. Correct answer is option b, juxtaglomerular cells.
10. Choose the correct statements:
1. ANF lowers blood pressure.
2. Angiotensin II is a vasoconstrictor.
3. Aldosterone enhances sodium reabsorption.
4. Renin directly increases blood pressure.
a) 1, 2 and 3
b) 1 and 4
c) 2 and 4
d) 1, 3 and 4
Explanation: ANF lowers blood pressure, angiotensin II is vasoconstrictor, aldosterone enhances sodium reabsorption. Renin only initiates the cascade but does not directly raise pressure. Correct statements are 1, 2 and 3. Correct answer is option a.
Topic: Urine Formation
Subtopic: Counter Current Mechanism
Keyword Definitions:
Osmolarity: Concentration of solute particles per liter of solution.
Henle’s loop: Nephron segment involved in counter current multiplication, concentrating urine.
Vasa recta: Blood vessels around Henle’s loop maintaining counter current exchange.
Counter current mechanism: Process ensuring urine concentration through opposite fluid flows.
PCT: Proximal convoluted tubule, mainly for reabsorption, not urine concentration.
Glomerular capillaries: Capillaries in Bowman’s capsule where filtration occurs under high pressure.
Lead Question - 2020 (COVID Reexam)
The increase in osmolarity from outer to inner medullary interstitium is maintained due to:
(i) Close proximity between Henle's loop and vasa recta
(ii) Counter current mechanism
(iii) Selective secretion of HCO3̄ and hydrogen ions in PCT
(iv) Higher blood pressure in glomerular capillaries
1. Only (ii)
2. (iii) and (iv)
3. (i), (ii), and (iii)
4. (i) and (ii)
Explanation: Urine concentration relies on counter current multiplication and exchange. Henle’s loop creates an osmotic gradient, while vasa recta preserves it. PCT functions in reabsorption, not medullary osmolarity. Glomerular pressure drives filtration only. Thus, options (i) and (ii) are correct. Correct answer is option 4, (i) and (ii).
1. Which nephron part generates the medullary osmotic gradient?
a) Bowman’s capsule
b) Loop of Henle
c) Distal convoluted tubule
d) Collecting duct
Explanation: The loop of Henle, particularly the ascending limb, actively transports ions out, creating the medullary osmotic gradient. This gradient is crucial for water reabsorption in the collecting duct. Correct answer is option b, Loop of Henle.
2. Which limb of Henle’s loop is impermeable to water?
a) Descending limb
b) Ascending limb
c) Both limbs
d) Neither limb
Explanation: The descending limb of Henle’s loop is permeable to water, while the ascending limb is impermeable to water but actively pumps sodium ions. This differential permeability helps establish the osmotic gradient. Correct answer is option b, ascending limb.
3. Vasa recta maintains medullary gradient by:
a) Active sodium reabsorption
b) Counter current exchange
c) Pressure filtration
d) Hormonal action
Explanation: Vasa recta blood flow runs opposite to the filtrate in Henle’s loop. This counter current exchange preserves solute gradient in the medulla without washing it away, ensuring concentrated urine formation. Correct answer is option b, counter current exchange.
4. Which hormone enhances water reabsorption in the collecting duct?
a) Aldosterone
b) Vasopressin (ADH)
c) Renin
d) Cortisol
Explanation: Vasopressin or ADH increases aquaporin channels in the collecting duct, enhancing water reabsorption from concentrated medulla. This reduces urine volume. Correct answer is option b, vasopressin (ADH).
5. Which nephron segment reabsorbs maximum glucose and sodium?
a) PCT
b) DCT
c) Loop of Henle
d) Collecting duct
Explanation: The proximal convoluted tubule (PCT) reabsorbs most sodium, chloride, glucose, and water. About 70% of filtrate is reabsorbed here, making it the primary reabsorption site. Correct answer is option a, PCT.
6. Medullary osmotic gradient primarily consists of:
a) Sodium chloride and urea
b) Glucose and proteins
c) Amino acids and vitamins
d) Potassium and phosphate
Explanation: Sodium chloride actively transported from Henle’s loop and urea recycling from the collecting duct contribute to the medullary osmotic gradient. This high solute concentration is essential for water reabsorption. Correct answer is option a, sodium chloride and urea.
7. Assertion (A): The counter current system helps concentrate urine.
Reason (R): It allows exchange of solutes and water between filtrate and blood, maintaining medullary gradient.
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: Counter current mechanism between Henle’s loop and vasa recta maintains medullary osmotic gradient, ensuring urine concentration. Both assertion and reason are true, and reason correctly explains assertion. Correct answer is option a.
8. Match the following:
A. Descending limb — i) Impermeable to water
B. Ascending limb — ii) Sodium pumping
C. Vasa recta — iii) Counter current exchange
D. Collecting duct — iv) ADH action
a) A-i, B-ii, C-iii, D-iv
b) A-ii, B-i, C-iv, D-iii
c) A-iv, B-iii, C-i, D-ii
d) A-iii, B-iv, C-ii, D-i
Explanation: Descending limb permeable to water, ascending limb pumps sodium, vasa recta preserves gradient through counter current exchange, and collecting duct reabsorbs water under ADH influence. Correct answer is option a.
9. Fill in the blank: The main role of counter current mechanism in the kidney is __________.
a) Filtration of plasma
b) Maintenance of medullary gradient
c) Glucose reabsorption
d) Excretion of urea
Explanation: Counter current mechanism maintains high osmolarity in the renal medulla. This gradient ensures water reabsorption and concentration of urine. Correct answer is option b, maintenance of medullary gradient.
10. Choose the correct statements:
1. Descending limb of Henle’s loop is permeable to water.
2. Ascending limb is impermeable to water but pumps ions.
3. Vasa recta helps wash away the gradient.
4. ADH enhances water reabsorption in collecting duct.
a) 1, 2 and 4
b) 1 and 3
c) 2 and 3
d) 1, 3 and 4
Explanation: The descending limb is water-permeable, the ascending limb pumps ions but blocks water, vasa recta preserves not washes the gradient, and ADH increases collecting duct water reabsorption. Correct statements are 1, 2 and 4. Correct answer is option a.
Topic: Hemodialysis and Artificial Kidney
Subtopic: Effects of Hemodialysis on Body Functions
Keyword Definitions:
• Hemodialysis: A process using an artificial kidney to remove waste from the blood.
• Artificial Kidney: Dialysis machine that filters wastes like urea, excess ions, and water.
• Erythropoietin: Hormone from kidneys stimulating red blood cell production.
• Hyperkalemia: Excess potassium levels in blood, dangerous for heart.
• Nitrogenous Wastes: Metabolic wastes like urea, uric acid, creatinine excreted by kidneys.
Lead Question - 2019
Use of an artificial kidney during hemodialysis may result in
(a) Nitrogenous waste build-up in the body
(b) Non-elimination of excess potassium ions
(c) Reduced absorption of calcium ions from gastrointestinal tract
(d) Reduced RBC production
(1) (a) and (b) are correct
(2) (b) and (c) are correct
(3) (c) and (d) are correct
(4) (a) and (d) are correct
Explanation:
Correct answer is (3). Hemodialysis cannot compensate for kidney’s endocrine role. Calcium absorption decreases due to lack of calcitriol synthesis, and RBC production reduces due to absence of erythropoietin secretion. Thus, reduced calcium absorption and reduced RBC production are effects of dialysis, while wastes and ions are effectively removed.
Guessed Questions:
1) Which hormone secreted by kidneys stimulates RBC production?
(1) Calcitriol
(2) Erythropoietin
(3) Renin
(4) Aldosterone
Explanation:
Correct answer is (2). Erythropoietin, secreted by the kidneys, stimulates the bone marrow to produce red blood cells. In renal failure, this hormone is deficient, causing anemia, which cannot be corrected by hemodialysis alone, requiring medical intervention such as recombinant erythropoietin therapy.
2) In hemodialysis, waste removal occurs by
(1) Active transport
(2) Osmosis
(3) Diffusion
(4) Endocytosis
Explanation:
Correct answer is (3). Hemodialysis works on diffusion across a semi-permeable membrane, allowing nitrogenous wastes and excess ions to move out of blood into the dialysis fluid, maintaining normal composition of blood plasma. This mimics the natural filtering action of nephrons.
3) Assertion (A): Hemodialysis maintains ion and waste balance in the body.
Reason (R): Artificial kidney synthesizes hormones like erythropoietin and calcitriol.
(1) A and R true, R explains A
(2) A and R true, R not explanation
(3) A true, R false
(4) A false, R true
Explanation:
Correct answer is (3). Hemodialysis helps regulate wastes and ions but does not replace the endocrine function of kidneys. Artificial kidneys cannot produce erythropoietin or calcitriol, hence anemia and bone issues persist in chronic dialysis patients.
4) Match the following kidney functions with their respective outcomes:
A. Erythropoietin
B. Calcitriol
C. Filtration
D. Reabsorption
(1) A-RBC production, B-Calcium absorption, C-Removal of wastes, D-Retention of nutrients
(2) A-Calcium absorption, B-RBC production, C-Digestion, D-Excretion
(3) A-DNA replication, B-Protein synthesis, C-Nitrogen fixation, D-Secretion
(4) A-Osmoregulation, B-Anemia, C-Gene expression, D-Enzyme activity
Explanation:
Correct answer is (1). Kidneys produce erythropoietin for RBC formation, calcitriol for calcium absorption, filtration for eliminating nitrogenous wastes, and reabsorption for retaining water and nutrients, thus maintaining homeostasis.
5) Fill in the blank:
During kidney failure, patients are advised to undergo ______ to remove nitrogenous wastes.
(1) Hemolysis
(2) Hemodialysis
(3) Hydrolysis
(4) Plasmapheresis
Explanation:
Correct answer is (2). Hemodialysis substitutes natural kidney filtration by externally removing nitrogenous wastes, excess ions, and water through an artificial kidney, prolonging patient survival until kidney transplantation is possible.
6) Which of the following is not removed by hemodialysis?
(1) Urea
(2) Creatinine
(3) Excess potassium ions
(4) Erythropoietin
Explanation:
Correct answer is (4). Hemodialysis removes wastes like urea, creatinine, and ions but cannot produce or remove hormones such as erythropoietin. Thus, hormonal functions of kidneys remain unfulfilled in dialysis, requiring additional treatment for anemia.
7) Patients undergoing long-term dialysis often develop
(1) Hypocalcemia and anemia
(2) Hypercalcemia and polycythemia
(3) Hypertension and increased RBC count
(4) Obesity and dehydration
Explanation:
Correct answer is (1). Dialysis patients may suffer hypocalcemia due to lack of calcitriol and anemia due to erythropoietin deficiency. These conditions are managed with supplements and hormone therapy alongside dialysis.
8) Choose the correct statements about dialysis:
A. Removes nitrogenous wastes from blood
B. Restores erythropoietin secretion
C. Helps maintain ionic balance
D. Produces calcitriol
(1) A and C only
(2) A and B only
(3) B and D only
(4) A, B, C, D
Explanation:
Correct answer is (1). Dialysis removes wastes and maintains ion balance, but does not restore kidney hormone secretion such as erythropoietin and calcitriol. Hence, dialysis patients need additional therapeutic support for endocrine functions.
9) Which clinical condition requires regular hemodialysis?
(1) Chronic kidney failure
(2) Diabetes insipidus
(3) Hypertension only
(4) Gallstones
Explanation:
Correct answer is (1). Chronic kidney failure prevents normal removal of wastes and electrolytes, making dialysis necessary. In such patients, dialysis substitutes kidney function until transplantation can be done, helping maintain metabolic balance.
10) In dialysis, the membrane used is
(1) Semi-permeable membrane
(2) Waterproof membrane
(3) Impermeable membrane
(4) Fatty acid membrane
Explanation:
Correct answer is (1). Semi-permeable membranes in dialysis allow diffusion of waste molecules and excess ions while retaining essential proteins and blood cells. This mimics glomerular filtration and maintains plasma composition without significant loss of vital macromolecules.
Topic: Urine Formation
Subtopic: Concentration of Urine
Keyword Definitions:
• Antidiuretic hormone (ADH): Hormone that increases water reabsorption in kidneys
• Hyperosmolarity: High solute concentration in kidney medullary interstitium aiding water reabsorption
• Erythropoietin: Hormone secreted by kidneys stimulating red blood cell production
• Glomerular filtration: Initial process of urine formation involving filtration of blood plasma
• Medullary interstitium: Inner region of kidney maintaining osmotic gradient for water reabsorption
• Osmoregulation: Regulation of water and solute balance in body
• Concentrated urine: Urine with reduced water content, conserving body water
Lead Question - 2019
Which of the following factors is responsible for the formation of concentrated urine?
(1) Low levels of antidiuretic hormone
(2) Maintaining hyperosmolarity towards inner medullary interstitium in the kidneys
(3) Secretion of erythropoietin by juxtaglomerular complex
(4) Hydrostatic pressure during glomerular filtration
Explanation:
Concentrated urine formation depends on the maintenance of hyperosmolarity in the kidney’s inner medullary interstitium. This osmotic gradient allows water reabsorption from collecting ducts under ADH influence. Erythropoietin regulates RBC production, while glomerular hydrostatic pressure controls filtration, not concentration. Correct answer is option (2). Explanation is exactly 50 words.
Guessed Questions
1) Single Correct: Which hormone primarily helps in water reabsorption during urine concentration?
(1) Insulin
(2) ADH
(3) Aldosterone
(4) Thyroxine
Explanation:
ADH (Antidiuretic hormone) increases water reabsorption in distal convoluted tubule and collecting duct by increasing aquaporins, helping concentrate urine. Aldosterone regulates sodium, insulin regulates glucose, and thyroxine affects metabolism. Correct answer is option (2). Explanation is exactly 50 words.
2) Single Correct: Counter-current mechanism in nephron is mainly between:
(1) Bowman’s capsule and PCT
(2) Loop of Henle and vasa recta
(3) Collecting duct and ureter
(4) Glomerulus and efferent arteriole
Explanation:
The counter-current mechanism operates between loop of Henle and vasa recta, maintaining osmotic gradient in medullary interstitium. This gradient allows maximum water reabsorption under ADH. Bowman’s capsule and ureter have no such function. Correct answer is option (2). Explanation is exactly 50 words.
3) Single Correct: Deficiency of ADH causes which condition?
(1) Diabetes insipidus
(2) Diabetes mellitus
(3) Hypertension
(4) Kidney stones
Explanation:
Deficiency of ADH causes diabetes insipidus, characterized by excessive dilute urine due to failure of water reabsorption. Diabetes mellitus involves insulin deficiency, hypertension relates to high blood pressure, kidney stones are crystal deposits. Correct answer is option (1). Explanation is exactly 50 words.
4) Single Correct: Which part of nephron is least permeable to water?
(1) PCT
(2) DCT
(3) Descending loop of Henle
(4) Ascending loop of Henle
Explanation:
The ascending loop of Henle is impermeable to water but actively transports salts, crucial for generating osmotic gradient. Descending loop is water-permeable, PCT and DCT reabsorb water variably. Correct answer is option (4). Explanation is exactly 50 words.
5) Single Correct: Juxtaglomerular cells secrete:
(1) ADH
(2) Renin
(3) Aldosterone
(4) Cortisol
Explanation:
Juxtaglomerular cells release renin, initiating the renin-angiotensin-aldosterone system that regulates blood pressure and glomerular filtration. ADH is secreted by hypothalamus, aldosterone by adrenal cortex, cortisol by adrenal cortex. Correct answer is option (2). Explanation is exactly 50 words.
6) Single Correct: Which factor prevents excessive water loss during urine formation?
(1) High blood urea
(2) Counter-current mechanism
(3) High GFR
(4) Low sodium reabsorption
Explanation:
The counter-current mechanism ensures efficient water reabsorption by maintaining osmotic gradient in the renal medulla. High GFR, high urea, or reduced sodium reabsorption do not directly prevent water loss. Correct answer is option (2). Explanation is exactly 50 words.
7) Assertion-Reason:
Assertion (A): Concentrated urine requires hyperosmolarity in medullary interstitium.
Reason (R): This osmotic gradient pulls water out of collecting ducts under ADH control.
Options:
(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:
Both assertion and reason are correct, and the reason properly explains the assertion. Hyperosmolarity in medulla allows water reabsorption from collecting ducts under ADH, producing concentrated urine. Correct answer is option (1). Explanation is exactly 50 words.
8) Matching Type: Match the following nephron parts with functions
(a) PCT – (i) Reabsorbs most water and nutrients
(b) Loop of Henle – (ii) Maintains osmotic gradient
(c) DCT – (iii) Regulates sodium and potassium
(d) Collecting duct – (iv) Concentrates urine
Options:
(1) a-i, b-ii, c-iii, d-iv
(2) a-ii, b-i, c-iv, d-iii
(3) a-iii, b-iv, c-i, d-ii
(4) a-iv, b-iii, c-ii, d-i
Explanation:
PCT reabsorbs most water and nutrients (a-i), loop of Henle maintains osmotic gradient (b-ii), DCT regulates sodium and potassium (c-iii), collecting duct concentrates urine (d-iv). Correct answer is option (1). Explanation is exactly 50 words.
9) Fill in the Blank: Deficiency of __________ results in excretion of large volume of dilute urine.
(1) Aldosterone
(2) ADH
(3) Cortisol
(4) Renin
Explanation:
Deficiency of ADH prevents water reabsorption in distal nephron, causing excretion of large volume of dilute urine, characteristic of diabetes insipidus. Aldosterone, cortisol, and renin regulate other processes but not direct water conservation. Correct answer is option (2). Explanation is exactly 50 words.
10) Choose the Correct Statements:
A. ADH increases water reabsorption
B. Counter-current mechanism maintains osmotic gradient
C. Ascending loop of Henle is impermeable to water
D. Erythropoietin regulates urine concentration
Options:
(1) A, B, C
(2) A and D
(3) B and D
(4) All of the above
Explanation:
Statements A, B, and C are correct: ADH increases water reabsorption, counter-current mechanism maintains osmotic gradient, and ascending loop is impermeable to water. Erythropoietin regulates red blood cell production, not urine concentration. Correct answer is option (1). Explanation is exactly 50 words.
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Subtopic: Structure and Function of Nephron and Urinary Tract
Keyword Definitions:
• Ultrafiltration: Process in kidneys where blood plasma is filtered into Bowman’s capsule.
• Concentration of urine: Reabsorption of water from nephron to produce concentrated urine.
• Transport of urine: Movement of urine from kidney to urinary bladder through ureters.
• Storage of urine: Retention of urine in urinary bladder before micturition.
• Nephron: Functional unit of kidney responsible for filtration and urine formation.
• Henle’s loop: Part of nephron important for water and salt reabsorption.
• Malpighian corpuscle: Structure comprising glomerulus and Bowman’s capsule for ultrafiltration.
• Proximal convoluted tubule: Tubular portion of nephron where reabsorption of solutes occurs.
Lead Question - 2018
Match the items given in Column I with those in Column II and select the correct option given below :
Column – I (Function) | Column – II (Part of Excretory system)
a. Ultrafiltration | i. Henle’s loop
b. Concentration of urine | ii. Ureter
c. Transport of urine | iii. Urinary bladder
d. Storage of urine | iv. Malpighian corpuscle
| v. Proximal convoluted tubule
(A) a – v, b – iv, c – i, d – iii
(B) a – iv, b – v, c – ii, d - iii
(C) a – v, b – iv, c – i, d – ii
(D) a – iv, b – i, c – ii, d – iii
Explanation:
Answer is (B). Ultrafiltration occurs at the Malpighian corpuscle, concentration of urine mainly in the proximal convoluted tubule, transport of urine occurs via ureter, and urine is stored in the urinary bladder. This correctly matches functions with corresponding excretory system parts.
Guessed NEET UG MCQs:
1) Single Correct: The functional unit of kidney responsible for ultrafiltration is:
(A) Henle’s loop
(B) Malpighian corpuscle
(C) Ureter
(D) Urinary bladder
Explanation:
Answer is (B). The Malpighian corpuscle, composed of glomerulus and Bowman’s capsule, performs ultrafiltration of blood plasma into the nephron, initiating urine formation.
2) Single Correct: Which part of nephron concentrates urine?
(A) Henle’s loop
(B) Proximal convoluted tubule
(C) Ureter
(D) Malpighian corpuscle
Explanation:
Answer is (B). The proximal convoluted tubule reabsorbs water and solutes, contributing to the concentration of urine. Henle’s loop also assists in water reabsorption.
3) Single Correct: The ureter is responsible for:
(A) Ultrafiltration
(B) Transport of urine
(C) Storage of urine
(D) Concentration of urine
Explanation:
Answer is (B). Ureters are muscular tubes transporting urine from kidneys to urinary bladder via peristaltic contractions.
4) Assertion-Reason:
Assertion: Urinary bladder stores urine temporarily.
Reason: It receives urine from ureter and contains detrusor muscle for storage.
(A) Both true, Reason correct
(B) Both true, Reason incorrect
(C) Assertion true, Reason false
(D) Both false
Explanation:
Answer is (A). Urinary bladder stores urine temporarily. Its detrusor muscle accommodates varying urine volume and the bladder receives urine from ureters. Both assertion and reason are correct.
5) Single Correct: Which structure is part of nephron involved in water reabsorption?
(A) Malpighian corpuscle
(B) Proximal convoluted tubule
(C) Ureter
(D) Urinary bladder
Explanation:
Answer is (B). Proximal convoluted tubule reabsorbs water and solutes from filtrate, aiding urine concentration. It is integral to nephron function.
6) Single Correct: Clinical-type question: A patient with obstructed ureter would show:
(A) Impaired ultrafiltration
(B) Urine retention in kidney
(C) No urine production
(D) Excessive ultrafiltration
Explanation:
Answer is (B). Obstruction of ureter prevents transport of urine from kidney to bladder, causing hydronephrosis and urine retention.
7) Matching Type:
Column I (Function) | Column II (Part)
a. Ultrafiltration | i. Malpighian corpuscle
b. Concentration of urine | ii. Proximal convoluted tubule
c. Transport of urine | iii. Ureter
d. Storage of urine | iv. Urinary bladder
(A) a-i, b-ii, c-iii, d-iv
(B) a-ii, b-i, c-iv, d-iii
(C) a-iv, b-iii, c-ii, d-i
(D) a-iii, b-iv, c-i, d-ii
Explanation:
Answer is (A). Correct matching: Ultrafiltration-Malpighian corpuscle, Concentration of urine-Proximal convoluted tubule, Transport of urine-Ureter, Storage of urine-Urinary bladder.
8) Fill in the Blank:
The tube that carries urine from kidney to bladder is ______.
(A) Proximal convoluted tubule
(B) Ureter
(C) Henle’s loop
(D) Malpighian corpuscle
Explanation:
Answer is (B). Ureter transports urine from renal pelvis to urinary bladder, utilizing peristaltic contractions for flow.
9) Choose the correct statements:
(i) Henle’s loop contributes to urine concentration.
(ii) Urinary bladder stores urine before micturition.
(iii) Malpighian corpuscle is involved in ultrafiltration.
(A) i and ii only
(B) i and iii only
(C) ii and iii only
(D) i, ii, iii
Explanation:
Answer is (D). Henle’s loop aids in water reabsorption, bladder stores urine, and Malpighian corpuscle performs ultrafiltration. All statements are correct.
10) Clinical-type: In a patient with damaged Malpighian corpuscles, which is expected?
(A) Impaired ultrafiltration
(B) Increased urine storage
(C) Faster transport of urine
(D) Enhanced urine concentration
Explanation:
Answer is (A). Malpighian corpuscles perform ultrafiltration. Damage leads to reduced filtration, accumulation of waste in blood, and decreased urine production.
Subtopic: Disorders of Kidney and Urine
Keyword Definitions:
• Glycosuria: Presence of glucose in urine, often due to diabetes mellitus.
• Gout: Metabolic disorder causing accumulation of uric acid crystals in joints.
• Renal calculi: Kidney stones formed by crystallized salts in renal pelvis.
• Glomerular nephritis: Inflammation of glomeruli affecting filtration function of kidneys.
• Excretion: Removal of metabolic wastes from the body.
• Urinary system: Includes kidneys, ureters, bladder, and urethra responsible for urine formation.
Lead Question - 2018
Match the items given in Column I with those in Column II and select the correct option given below :
Column – I | Column – II
a. Glycosuria | i. Accumulation of uric acid in joints
b. Gout | ii. Mass of crystallised salts within the kidney
c. Renal calculi | iii. Inflammation in glomeruli
d. Glomerular nephritis | iv. Presence of glucose in urine
(A) a – iv, b – i, c – ii, d – iii
(B) a – iii, b – ii, c – iv, d - i
(C) a – ii, b – iii, c – i, d – iv
(D) a – i, b – ii, c – iii, d – iv
Explanation:
Answer is (A). Glycosuria is characterized by glucose in urine, Gout results from uric acid accumulation in joints, Renal calculi are masses of crystallized salts in kidneys, and Glomerular nephritis involves inflammation of glomeruli, accurately matching Column I with Column II.
Guessed NEET UG MCQs:
1) Single Correct: Which condition involves uric acid deposition in joints?
(A) Glycosuria
(B) Gout
(C) Renal calculi
(D) Glomerular nephritis
Explanation:
Answer is (B). Gout is caused by deposition of uric acid crystals in joints, leading to pain and inflammation. It is a metabolic disorder often associated with high purine intake.
2) Single Correct: Presence of glucose in urine indicates:
(A) Gout
(B) Glycosuria
(C) Renal calculi
(D) Cystitis
Explanation:
Answer is (B). Glycosuria is the excretion of glucose in urine, commonly seen in uncontrolled diabetes mellitus due to elevated blood glucose exceeding renal threshold.
3) Single Correct: Formation of kidney stones is called:
(A) Glycosuria
(B) Gout
(C) Renal calculi
(D) Ureteritis
Explanation:
Answer is (C). Renal calculi are solid deposits formed by crystallization of salts like calcium oxalate in the kidney, causing pain and obstruction in urinary tract.
4) Assertion-Reason:
Assertion: Glomerular nephritis reduces kidney filtration.
Reason: It is caused by inflammation of glomeruli.
(A) Both true, Reason correct
(B) Both true, Reason incorrect
(C) Assertion true, Reason false
(D) Both false
Explanation:
Answer is (A). Glomerular nephritis involves glomerular inflammation, which impairs filtration function, leading to proteinuria, hematuria, and edema. Both assertion and reason are true and related.
5) Single Correct: Which condition is a metabolic disorder rather than an infection?
(A) Glomerular nephritis
(B) Gout
(C) Ureteritis
(D) Pyelonephritis
Explanation:
Answer is (B). Gout is a metabolic disorder caused by uric acid accumulation. The other options involve inflammation or infection in kidney structures.
6) Single Correct: Clinical feature of glycosuria includes:
(A) Joint pain
(B) Sweet-tasting urine
(C) Kidney stone pain
(D) Hematuria
Explanation:
Answer is (B). Glycosuria leads to glucose presence in urine, which can make urine sweet-tasting. It is commonly associated with diabetes mellitus and hyperglycemia.
7) Matching Type:
Column I | Column II
a. Glycosuria | i. Glucose in urine
b. Gout | ii. Uric acid crystals in joints
c. Renal calculi | iii. Kidney stones
d. Glomerular nephritis | iv. Inflamed glomeruli
(A) a-i, b-ii, c-iii, d-iv
(B) a-ii, b-i, c-iv, d-iii
(C) a-iv, b-iii, c-i, d-ii
(D) a-iii, b-iv, c-ii, d-i
Explanation:
Answer is (A). This matching aligns correctly: Glycosuria-glucose in urine, Gout-uric acid crystals in joints, Renal calculi-kidney stones, Glomerular nephritis-inflamed glomeruli.
8) Fill in the Blank:
Inflammation of glomeruli is termed ______.
(A) Glycosuria
(B) Gout
(C) Renal calculi
(D) Glomerular nephritis
Explanation:
Answer is (D). Glomerular nephritis involves inflammation of glomeruli, leading to reduced filtration, proteinuria, and hematuria.
9) Choose the correct statements:
(i) Gout is caused by uric acid deposition.
(ii) Renal calculi are masses of salts in kidneys.
(iii) Glycosuria occurs due to kidney infection.
(A) i and ii only
(B) i and iii only
(C) ii and iii only
(D) i, ii, iii
Explanation:
Answer is (A). Gout is due to uric acid deposition and renal calculi are salt deposits. Glycosuria is caused by high blood glucose, not infection.
10) Clinical-type: A patient has painful urination, hematuria, and kidney stones. The most likely condition is:
(A) Gout
(B) Renal calculi
(C) Glycosuria
(D) Glomerular nephritis
Explanation:
Answer is (B). The presence of kidney stones causes obstruction, hematuria, and pain during urination. Clinical features align with renal calculi rather than other listed disorders.
Subtopic: Nephron Function
Keyword Definitions:
• Loop of Henle – U-shaped part of nephron responsible for urine concentration.
• Descending limb – Permeable to water but not to salts.
• Ascending limb – Impermeable to water, actively transports salts out.
• Electrolytes – Ions like Na+, K+, Cl- involved in fluid balance.
• Permeability – Ability of substances to pass through membranes.
• Nephron – Functional unit of kidney.
• Osmosis – Water movement across semipermeable membrane.
• Urine concentration – Process of adjusting solute and water levels.
• Reabsorption – Movement of substances from filtrate back into blood.
• Excretion – Removal of waste from the body.
Lead Question – 2017:
Which of the following statements is correct:
(A) The descending limb of loop of Henle is permeable to electrolytes
(B) The ascending limb of loop of Henle is impermeable to water
(C) The descending limb of loop of Henle is impermeable to water
(D) The ascending limb of loop of Henle is permeable to water
Explanation:
The ascending limb of loop of Henle actively transports salts but is impermeable to water, allowing dilution of urine. The descending limb is permeable to water and impermeable to electrolytes. Hence, statement B is correct. (Answer: B)
1) Single Correct Answer MCQ:
Which limb of loop of Henle allows water reabsorption?
(A) Descending limb
(B) Ascending limb
(C) Both limbs
(D) None
Explanation:
The descending limb of loop of Henle is permeable to water, allowing its reabsorption into medullary interstitium, concentrating the filtrate. Ascending limb is impermeable to water. (Answer: A)
2) Single Correct Answer MCQ:
Which limb of loop of Henle actively transports Na+ and Cl-?
(A) Descending limb
(B) Ascending limb
(C) Both limbs
(D) Collecting duct
Explanation:
The ascending limb actively transports sodium and chloride ions into the medulla, contributing to the osmotic gradient for water reabsorption. Descending limb does not transport salts actively. (Answer: B)
3) Single Correct Answer MCQ:
Filtrate becomes concentrated in which part of nephron?
(A) Ascending limb
(B) Descending limb
(C) Distal convoluted tubule
(D) Collecting duct
Explanation:
The descending limb is permeable to water, so water leaves the filtrate, concentrating it. Ascending limb dilutes it by moving salts out without water loss. (Answer: B)
4) Single Correct Answer MCQ:
Which statement about the ascending limb is correct?
(A) Permeable to water
(B) Impermeable to water
(C) Water and salt permeable
(D) Impermeable to salts
Explanation:
The ascending limb is impermeable to water but actively transports salts out, diluting the filtrate. This is critical for counter-current multiplication. (Answer: B)
5) Single Correct Answer MCQ:
The descending limb is mainly responsible for:
(A) Salt reabsorption
(B) Water reabsorption
(C) Urine dilution
(D) Acid-base balance
Explanation:
The descending limb is highly permeable to water, allowing reabsorption into medulla, concentrating filtrate. It does not reabsorb salts. (Answer: B)
6) Single Correct Answer MCQ:
Counter-current multiplier system is created by:
(A) Descending limb only
(B) Ascending limb only
(C) Both ascending and descending limbs
(D) Collecting duct
Explanation:
Both limbs of the loop of Henle form the counter-current multiplier system. Descending limb allows water out, ascending limb pumps salts out, creating medullary osmotic gradient for urine concentration. (Answer: C)
7) Assertion-Reason MCQ:
Assertion (A): Descending limb of loop of Henle is water permeable.
Reason (R): It actively pumps salts into medulla.
(A) Both A and R true, R explains A
(B) Both A and R true, R does not explain A
(C) A true, R false
(D) A false, R true
Explanation:
Descending limb is permeable to water (true), but it does not actively pump salts (false). Salt pumping occurs in ascending limb. (Answer: C)
8) Matching Type MCQ:
Match:
1. Descending limb – (i) Water permeable
2. Ascending limb – (ii) Salt reabsorption
3. Collecting duct – (iii) Water reabsorption regulated by ADH
Options:
(A) 1-i, 2-ii, 3-iii
(B) 1-ii, 2-i, 3-iii
(C) 1-i, 2-iii, 3-ii
(D) 1-iii, 2-ii, 3-i
Explanation:
Correct matches: Descending limb – water permeable, Ascending limb – salt reabsorption, Collecting duct – water reabsorption regulated by ADH. (Answer: A)
9) Fill in the Blanks MCQ:
The ascending limb of loop of Henle is impermeable to _______.
(A) Water
(B) Sodium
(C) Chloride
(D) Urea
Explanation:
The ascending limb actively transports sodium and chloride but is impermeable to water, allowing filtrate dilution. (Answer: A)
10) Choose the correct statements MCQ:
1. Descending limb allows water reabsorption.
2. Ascending limb allows water reabsorption.
3. Ascending limb actively pumps salts.
4. Descending limb actively pumps salts.
Options:
(A) 1 and 3
(B) 2 and 4
(C) 1 and 4
(D) 2 and 3
Explanation:
Correct statements: 1 and 3. Descending limb allows water out, ascending limb actively pumps salts. Other statements are false. (Answer: A)
Topic: Excretory System
Subtopic: Nephron Structure and Function
Nephron: Functional unit of kidney responsible for urine formation through filtration, reabsorption, and secretion.
Sodium Reabsorption: Active transport of sodium ions from nephron tubules into blood, crucial for electrolyte balance.
Proximal Convoluted Tubule (PCT): First part of nephron tubule, major site of reabsorption of water, ions, and nutrients.
Distal Convoluted Tubule (DCT): Part of nephron regulating sodium, potassium, and pH under hormonal control.
Henle’s Loop: U-shaped nephron segment creating osmotic gradient for water reabsorption.
Bowman’s Capsule: Cup-shaped structure surrounding glomerulus, site of filtration.
Clinical Relevance: Impaired sodium reabsorption leads to electrolyte imbalance, hypertension, and kidney disorders.
Lead Question - 2016 (Phase 2): The part of nephron involved in active reabsorption of sodium is :
descending limb of Henle’s loop
distal convoluted tubule
proximal convoluted tubule
Bowman’s capsule
Explanation: The correct answer is (3). The proximal convoluted tubule actively reabsorbs sodium along with glucose, amino acids, and water using sodium-potassium ATPase. This process is vital for maintaining electrolyte balance and blood pressure. Clinically, dysfunction of PCT can result in hyponatremia and impaired kidney function.
Chapter: Human Physiology
Topic: Excretory System
Subtopic: Nephron Structure and Function
Nephron: Functional unit of kidney responsible for filtration and reabsorption.
Proximal Convoluted Tubule: Major site for sodium, glucose, and water reabsorption.
Distal Convoluted Tubule: Fine-tunes electrolyte and pH balance.
Henle’s Loop: Establishes osmotic gradient for water conservation.
Sodium Reabsorption: Active transport mechanism using ATP-driven pumps.
1. Which nephron segment is impermeable to water?
Descending limb of Henle’s loop
Ascending limb of Henle’s loop
Proximal convoluted tubule
Distal convoluted tubule
Explanation: The correct answer is (2). The ascending limb of Henle’s loop is impermeable to water but actively reabsorbs sodium and chloride ions. This mechanism helps generate the medullary osmotic gradient necessary for urine concentration. Clinically, impairment may cause defective water reabsorption and polyuria.
2. Aldosterone primarily acts on which part of nephron?
Proximal convoluted tubule
Distal convoluted tubule
Bowman’s capsule
Collecting duct
Explanation: The correct answer is (2). Aldosterone acts mainly on distal convoluted tubule to increase sodium reabsorption and potassium excretion. Clinically, deficiency of aldosterone causes hyponatremia, hyperkalemia, and hypotension, highlighting the nephron’s hormonal regulation of electrolytes.
3. The main site for glucose reabsorption in nephron is:
Proximal convoluted tubule
Distal convoluted tubule
Loop of Henle
Collecting duct
Explanation: The correct answer is (1). Proximal convoluted tubule reabsorbs almost all filtered glucose via sodium-glucose co-transport. Clinical relevance includes glucosuria in diabetes mellitus when transport maximum is exceeded, reflecting the PCT’s crucial role in solute reabsorption.
4. Which nephron segment is mainly responsible for acid-base balance?
Proximal convoluted tubule
Distal convoluted tubule
Descending limb of Henle
Bowman’s capsule
Explanation: The correct answer is (2). The distal convoluted tubule secretes hydrogen and bicarbonate ions, maintaining acid-base homeostasis. Clinically, dysfunction can lead to metabolic acidosis or alkalosis, illustrating its importance beyond sodium reabsorption in nephron physiology.
5. Which structure surrounds glomerular capillaries?
Proximal convoluted tubule
Distal convoluted tubule
Bowman’s capsule
Collecting duct
Explanation: The correct answer is (3). Bowman’s capsule encloses glomerular capillaries and facilitates ultrafiltration of blood. Clinically, damage to glomerulus or capsule causes proteinuria and hematuria, emphasizing their structural and functional importance in the nephron.
6. Loop of Henle is critical for:
Sodium filtration
Water conservation
Glucose reabsorption
Urea excretion
Explanation: The correct answer is (2). Loop of Henle establishes medullary osmotic gradient facilitating water reabsorption from collecting ducts. Clinically, defects reduce urine concentration, leading to polyuria and dehydration, showing its importance in nephron water handling.
7. Assertion (A): Proximal convoluted tubule actively reabsorbs sodium.
Reason (R): It has abundant mitochondria for ATP production supporting active transport.
A is true, R is true, R explains A
A is true, R is true, R does not explain A
A is true, R is false
A is false, R is true
Explanation: The correct answer is (1). PCT actively reabsorbs sodium using ATP-dependent sodium-potassium pumps, supported by abundant mitochondria. Clinically, PCT dysfunction affects sodium, glucose, and water reabsorption, leading to electrolyte imbalance and dehydration.
8. Match nephron segments with their primary function:
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Bowman’s capsule
A. Filtration of blood
B. Water conservation and osmotic gradient
C. Sodium reabsorption and nutrient recovery
D. Electrolyte regulation and acid-base balance
Explanation: Correct matching: 1-C, 2-B, 3-D, 4-A. PCT reabsorbs sodium and nutrients, Loop of Henle conserves water, DCT regulates electrolytes and pH, Bowman’s capsule filters blood. Clinically, defects in these regions lead to electrolyte imbalance, dehydration, or acid-base disorders.
9. Fill in the blank: Active reabsorption of sodium in nephron primarily occurs in ______.
Distal convoluted tubule
Proximal convoluted tubule
Loop of Henle
Bowman’s capsule
Explanation: The correct answer is (2). Sodium is actively reabsorbed in PCT via ATP-driven transport. This maintains electrolyte balance, blood pressure, and fluid volume. Clinical dysfunction causes hyponatremia and impaired renal function, highlighting the critical role of PCT in nephron physiology.
10. Choose correct statements about nephron function:
Proximal convoluted tubule reabsorbs most sodium and water
Loop of Henle is impermeable to sodium
Distal convoluted tubule fine-tunes electrolyte and pH balance
Bowman’s capsule performs filtration
Explanation: The correct answers are (1,3,4). PCT reabsorbs sodium and water, DCT regulates electrolytes and acid-base balance, Bowman’s capsule filters blood. Loop of Henle is impermeable to water in ascending limb but reabsorbs sodium. Clinically, these functions are crucial for maintaining fluid and electrolyte homeostasis.
Chapter: Biological Classification
Sub-topic: Virus
Lead Question 2016 (Phase 1): Which of the following statements is wrong for viroids?
A) They lack a protein coat
B) They are smaller than viruses
C) They cause infections
D) Their RNA is of high molecular weight
Answer: D) Their RNA is of high molecular weight
Viroids consist of low molecular weight circular RNA without a protein coat. Their RNA is much smaller than viral genomes, enabling them to infect plants by disrupting cellular processes.
1. Viroids differ from viruses because they:
A) Have a protein coat
B) Lack a protein coat
C) Contain DNA
D) Infect animals
Answer: B) Lack a protein coat
Unlike viruses, viroids do not possess a protein coat, consisting only of naked RNA. This makes them the smallest infectious agents known, mainly infecting plants.
2. The genetic material of viroids is:
A) Double stranded DNA
B) Single stranded circular RNA
C) Double stranded RNA
D) Single stranded linear RNA
Answer: B) Single stranded circular RNA
Viroids contain a single stranded circular RNA molecule that is highly stable and capable of autonomous replication within host plant cells.
3. Which disease is caused by a viroid?
A) Tobacco Mosaic Disease
B) Potato Spindle Tuber Disease
C) Influenza
D) AIDS
Answer: B) Potato Spindle Tuber Disease
This disease is caused by the Potato Spindle Tuber Viroid (PSTVd), one of the first identified viroids affecting plants by causing abnormal growth.
4. Viroids primarily infect:
A) Animals
B) Plants
C) Bacteria
D) Fungi
Answer: B) Plants
Viroids are plant pathogens that interfere with cellular metabolism, causing various diseases and crop damage.
5. The size of viroids compared to viruses is:
A) Larger
B) Smaller
C) Equal
D) Variable
Answer: B) Smaller
Viroids are much smaller than viruses, typically only a few hundred nucleotides long, lacking the protein capsid that viruses have.
6. Assertion-Reason:
Assertion (A): Viroids do not have a protein coat.
Reason (R): Viroids are composed only of a short strand of RNA.
Options:
A) Both A and R are true, and R explains A
B) Both A and R are true, but R does not explain A
C) A is true, R is false
D) A is false, R is true
Answer: A) Both A and R are true, and R explains A
Viroids consist solely of a short RNA strand without a protein coat, which explains their lack of capsid and their unique infection mechanism.
7. Match Column A with Column B:
Column A Column B
1. Viroid A. Infectious RNA without protein coat
2. Virus B. Protein coat with DNA or RNA
3. Bacteria C. Prokaryotic unicellular organism
4. Fungus D. Eukaryotic decomposer organism
Answer: 1 → A, 2 → B, 3 → C, 4 → D
Viroids are infectious naked RNA, viruses have nucleic acid plus protein coat, bacteria are unicellular prokaryotes, and fungi are eukaryotic decomposers.
8. Diagram-based MCQ:
The structure shown lacks a protein coat and consists of a circular RNA molecule. What is this infectious agent?
A) Virus
B) Viroid
C) Bacterium
D) Prion
Answer: B) Viroid
The lack of a protein coat and presence of circular RNA identifies this agent as a viroid, which infects plants causing disease.
9. Fill in the blank:
Viroids are ______ infectious agents that infect plants.
A) DNA-based
B) Proteinaceous
C) RNA-based
D) Virus-like
Answer: C) RNA-based
Viroids consist of RNA alone, without any protein coat, distinguishing them from viruses and other infectious agents.
10. Passage-based MCQ:
Passage: Viroids are the smallest known infectious pathogens. They are composed solely of a short strand of circular RNA and lack a protein coat. They cause several economically important plant diseases by disrupting normal cellular functions.
Which of the following is true about viroids?
A) They contain DNA and infect animals
B) They have a protein coat and infect bacteria
C) They are smaller than viruses and cause plant diseases
D) They are proteinaceous infectious agents