Excretory Products and Their EliminationNEET MCQs with solutions
Excretory Products and Their Elimination explains how animals remove nitrogenous waste and how the human kidney makes and concentrates urine. NEET questions test the modes of excretion with examples, the role of each part of the nephron, the counter-current mechanism and the hormones that regulate the kidney.
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- 11 Biology
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Practise 24 questions
Tap an option to check it. Questions from every NCERT topic in this chapter, from easy to hard.
Q1Types of Nitrogenous Wastes
Urea is synthesized from ammonia in the liver by which cycle?
Not quite — the answer is C.
Urea synthesis occurs exclusively via the ornithine cycle (urea cycle) in the liver — ammonia is combined with CO₂ to ultimately produce urea. The Krebs cycle (Option A) is the top distractor as it also occurs in the liver, but it functions in energy production, not urea synthesis.
Q2Types of Nitrogenous Wastes
Animals living in arid or desert environments are predominantly:
Not quite — the answer is D.
Uricotelic animals excrete uric acid as a nearly dry semi-solid paste, losing minimal water — the maximum water conservation strategy. Ureotelic animals still need water to dilute urine; ammonotelic animals need the most water. Desert reptiles, birds, and insects are uricotelic.
Q3Types of Nitrogenous Wastes
Which of the following correctly explains why ureotelic animals can survive moderate water scarcity better than ammonotelic animals?
Not quite — the answer is C.
Urea's lower toxicity allows it to accumulate temporarily and be excreted in concentrated urine — far less water is needed than for toxic ammonia. Option D describes a reverse process that does not occur physiologically. Option B is incorrect: urea is stored transiently in blood, not muscles.
Q4Human Excretory System
Approximately what percentage of nephrons in the human kidney are juxtamedullary?
Not quite — the answer is B.
About 15% of nephrons are juxtamedullary (with long loops of Henle); the remaining ~85% are cortical nephrons with short loops. This ratio is frequently tested in NEET.
Q5Human Excretory System
Under resting conditions, kidneys receive approximately what fraction of resting cardiac output?
Not quite — the answer is C.
Kidneys receive ~1200 mL/min of blood, which is approximately one-fifth (20%) of the resting cardiac output of ~5000 mL/min. One-tenth (10%) and one-third are both incorrect values.
Q6Human Excretory System
Glomeruli are exclusively located in which region of the kidney?
Not quite — the answer is D.
Glomeruli, along with Bowman's capsules forming renal corpuscles, are exclusively cortical structures. Their presence in medulla would suggest a pathological condition; this is a common HARD-level NEET trap.
Q7Urine Formation
When blood glucose concentration exceeds the renal threshold and tubular maximum, which condition results?
Not quite — the answer is C.
When plasma glucose exceeds ~180 mg/dL (renal threshold), carriers saturate at Tm (~320 mg/min) and excess glucose cannot be reabsorbed, appearing in urine as glycosuria — hallmark of uncontrolled diabetes mellitus.
Q8Urine Formation
Urea recycling from the collecting duct back into the medullary interstitium contributes to which process?
Not quite — the answer is C.
Urea diffuses from the inner collecting duct into the medullary interstitium, contributing significantly to the high osmolarity of the medulla. This gradient is essential for water reabsorption from the descending limb and collecting duct.
Q9Urine Formation
The juxtaglomerular apparatus (JGA) regulates GFR primarily by sensing which two parameters?
Not quite — the answer is C.
JG cells in the afferent arteriole sense stretch (blood pressure), while macula densa cells sense NaCl concentration in tubular fluid. Together they trigger renin release and autoregulate GFR. Aldosterone/ADH act downstream of JGA signals.
Q10Function of Tubules
The descending limb of the loop of Henle allows passive movement of:
Not quite — the answer is D.
The descending limb is freely permeable to water (via aquaporin-1) but impermeable to Na⁺ and other electrolytes. As tubular fluid descends into the hypertonic medulla, water moves out osmotically, concentrating the tubular fluid. Na⁺, glucose, and K⁺ are not passively transported across the descending limb.
Q11Function of Tubules
Which of the following organic nutrients is significantly reabsorbed in the proximal convoluted tubule?
Not quite — the answer is D.
Amino acids are completely reabsorbed in the PCT via Na⁺-linked cotransporters (secondary active transport). Creatinine is not significantly reabsorbed and serves as a GFR marker. Inulin is neither reabsorbed nor secreted (used to measure GFR). Urea is partially reabsorbed but is a waste product, not an organic nutrient.
Q12Function of Tubules
Which of the following correctly explains why bicarbonate reabsorption in the proximal tubule is essential for acid-base balance?
Not quite — the answer is A.
~85% of filtered HCO₃⁻ is reabsorbed in the PCT via carbonic anhydrase-mediated reactions. This restores plasma bicarbonate, the primary extracellular buffer. Loss of HCO₃⁻ in urine would deplete plasma buffering capacity, causing metabolic acidosis. HCO₃⁻ is reabsorbed from — not secreted into — the lumen.
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Get RankUp on Google PlayQ13Mechanism of Concentration of Urine
The ability to produce concentrated urine is directly proportional to:
Not quite — the answer is C.
A longer loop of Henle allows the counter-current multiplier to create a steeper and deeper corticopapillary osmotic gradient. This gradient is what drives water reabsorption in the collecting duct. Glomerular number, cortical thickness, and pelvis size do not determine concentrating ability.
Q14Mechanism of Concentration of Urine
Desert mammals can produce highly concentrated urine mainly because they have:
Not quite — the answer is C.
Long loops of Henle allow the counter-current multiplier to establish a steeper and deeper osmotic gradient in the medulla, enabling greater water reabsorption. Desert mammals have evolved proportionally longer juxtamedullary nephron loops as an adaptation. Reduced ADH would have the opposite effect.
Q15Mechanism of Concentration of Urine
Which of the following best explains the mechanism by which ADH increases water reabsorption in the collecting duct?
Not quite — the answer is B.
ADH binds V2 receptors on collecting duct cells, activating adenylyl cyclase → cAMP → PKA pathway, which inserts pre-formed aquaporin-2 vesicles into the apical membrane. This increases water permeability dramatically. Sodium channels and GFR are not the mechanism of ADH action here.
Q16Regulation of Kidney Function
The macula densa is a specialised region of the:
Not quite — the answer is B.
Macula densa cells are tall, closely packed, modified epithelial cells of the DCT located at the point where the DCT contacts the afferent arteriole of the same nephron. They are the chemosensory component of the JGA. This is a high-frequency anatomical fact tested directly in NEET.
Q17Regulation of Kidney Function
Which of the following correctly explains the RAAS effect on blood volume?
Not quite — the answer is C.
Aldosterone (final RAAS effector) upregulates ENaC and Na⁺/K⁺-ATPase in DCT/collecting duct principal cells, increasing Na⁺ reabsorption. Retained Na⁺ raises plasma osmolarity, stimulating ADH release and osmotic water retention — net effect: increased blood volume and pressure. RAAS is activated by low BP, not high.
Q18Regulation of Kidney Function
Activation of sympathetic nervous system increases renin release primarily by:
Not quite — the answer is A.
Sympathetic nerve terminals directly innervate JG cells of the afferent arteriole. β₁ adrenergic receptor activation on JG cells triggers renin granule release — independent of the baroreceptor and macula densa pathways. This is why haemorrhage (sympathetic surge) rapidly activates RAAS. Aldosterone acts on DCT; it has no receptors on JG cells.
Q19Micturition
Which organ temporarily stores urine before elimination?
Not quite — the answer is C.
The urinary bladder is the storage organ for urine. The renal pelvis and ureter are conduits, while the collecting duct is part of the nephron involved in concentration, not storage.
Q20Micturition
Effective micturition requires simultaneous detrusor contraction and:
Not quite — the answer is D.
Voiding requires coordinated detrusor contraction combined with relaxation of both the internal (involuntary) and external (voluntary) sphincters. Sphincter closure would obstruct outflow and prevent micturition.
Q21Micturition
Which of the following correctly explains how higher brain centres influence micturition?
Not quite — the answer is C.
The cerebral cortex modulates the spinal reflex by exerting inhibitory or facilitatory control, enabling voluntary postponement or initiation of urination. This cortical override, not permanent suppression, is what allows social control of voiding.
Q22Disorders of Human Excretory System
Dialysis is the treatment of choice primarily in cases of:
Not quite — the answer is C.
Dialysis is indicated when kidneys fail to filter blood adequately, leading to dangerous accumulation of nitrogenous wastes. Renal calculi and UTI are managed by other interventions; hypertension alone does not require dialysis.
Q23Disorders of Human Excretory System
Urinary tract infection most characteristically results in:
Not quite — the answer is B.
UTI (typically bacterial) causes inflammation of the urinary tract lining, producing dysuria (painful urination) and increased frequency. It does not primarily affect GFR or plasma proteins — those point to glomerular disorders.
Q24Disorders of Human Excretory System
Which of the following correctly explains why proteinuria occurs in glomerular damage?
Not quite — the answer is C.
The glomerular filtration barrier (endothelium + basement membrane + podocytes) normally excludes large, negatively charged plasma proteins. Damage disrupts both size and charge selectivity, allowing proteins to enter the filtrate and appear in urine.
ELITE question · AIR under 50 level
This chapter has 55 ELITE questions for students aiming at the very top. They are only in the app.
Unlock ELITE questions in the appExcretion facts to remember
Quick revision: most questions in this chapter test these facts.
| Topic | Key fact |
|---|---|
| Ammonotelic | Bony fishes, aquatic amphibians, aquatic insects |
| Ureotelic | Mammals, many terrestrial amphibians, marine fishes |
| Uricotelic | Reptiles, birds, land snails, insects |
| Excretory structures | Flame cells/protonephridia (Platyhelminthes, rotifers, some annelids, Amphioxus); nephridia (earthworm); Malpighian tubules (insects); green glands (prawn) |
| Nephrons | About 1 million per kidney; about 15% are juxtamedullary with long loops of Henle |
| Filtration | GFR about 125 mL/min (180 L/day); nearly 99% is reabsorbed; about 1.5 L urine per day |
| PCT | Reabsorbs 70–80% of electrolytes and water, all glucose and amino acids; secretes H⁺, NH₃ and K⁺ |
| Loop of Henle | Descending limb permeable to water; ascending limb impermeable to water but lets electrolytes out |
| Counter-current mechanism | Loop of Henle and vasa recta keep the medulla concentrated (up to about 1200 mOsm/L) using NaCl and urea |
| ADH (vasopressin) | Increases water reabsorption from DCT and collecting duct |
| JGA and RAAS | Low GFR → renin → angiotensin II → aldosterone → more Na⁺ and water reabsorption; ANF from the heart opposes it |
| Urine | About 1–1.5 L per day, pH about 6; 25–30 g urea excreted daily |
| Other excretory organs | Lungs remove CO₂; liver excretes bilirubin and other substances in bile; skin through sweat and sebum |
| Disorders | Uremia (treated by haemodialysis), renal calculi, glomerulonephritis; glycosuria and ketonuria indicate diabetes mellitus |
What the app covers in this chapter
552 questions in total, each with a detailed explanation.
| Types of Nitrogenous Wastes | 41 |
| Human Excretory System | 40 |
| Urine Formation | 60 |
| Function of Tubules | 40 |
| Mechanism of Concentration of Urine | 39 |
| Regulation of Kidney Function | 41 |
| Micturition | 40 |
| Disorders of Human Excretory System | 42 |
| Mixed practice and chapter tests | 209 |
Questions students ask
Is Excretory Products and Their Elimination important for NEET?
Yes. It is a high-yield Zoology chapter. Questions test modes of excretion with examples, the function of each nephron segment, the counter-current mechanism and hormonal control by ADH, RAAS and ANF.
Which topics should I revise first?
Start with the three modes of excretion and their examples, then what each part of the nephron does, and finish with the counter-current mechanism and hormonal regulation (use the table on this page).
How many questions from this chapter are on RankUp?
The RankUp app has 552 questions on Excretory Products and Their Elimination, including 55 ELITE questions written for students aiming at AIR under 50. Every question has a detailed explanation.
Can I download these questions as a PDF?
Yes. The free PDF on this page has all 24 questions with the answer key and explanations. No signup is needed.
