Q10. Which compound is a major constituent of the most common human kidney stones?
[UPPCS Preliminary Re-examination (2015)]
(a) Calcium acetate
(b) Calcium oxalate
(c) Sodium acetate
(d) Sodium benzoate
Answer: (b) Calcium oxalate
Explanation: Calcium oxalate forms the most common type of kidney stone. Crystals can develop when urine becomes supersaturated with stone-forming substances. Not all kidney stones are calcium oxalate; other types include uric acid, struvite and cystine stones.
Q9. The excretory role of the kidneys most directly complements the metabolic role of which organ?
[RRB Senior Section Engineer (21 December 2014)]
(a) Liver
(b) Heart
(c) Large intestine
(d) Skin
Answer: (a) Liver
Explanation: The liver converts potentially dangerous ammonia from amino-acid breakdown into urea. Blood delivers urea to the kidneys, which filter and excrete it. These two organs therefore cooperate in nitrogen disposal, despite performing distinctly different biochemical and excretory tasks.
Q8. Which is NOT ordinarily regarded as a primary function of the human kidneys?
[UPPCS Preliminary Examination (2011)]
(a) Regulating body-water balance
(b) Controlling blood glucose mainly by secreting insulin
(c) Removing urea from blood
(d) Producing hormones such as renin
Answer: (b) Controlling blood glucose mainly by secreting insulin
Explanation: Kidneys remove wastes, regulate fluid and electrolyte balance, and produce hormones including renin and erythropoietin. The pancreas is the principal source of insulin governing blood-glucose regulation. Although kidneys also contribute to glucose handling, insulin secretion is not their function.
Q7. Which human organ is chiefly responsible for detoxifying ingested alcohol?
[UPPCS Mains General Studies (2010)]
(a) Liver
(b) Lungs
(c) Heart
(d) Kidneys
Answer: (a) Liver
Explanation: The liver metabolises most consumed alcohol. Alcohol dehydrogenase converts ethanol into acetaldehyde, and aldehyde dehydrogenase then converts acetaldehyde into acetate. The kidneys excrete some alcohol-related metabolites, but the major enzymatic breakdown of ethanol occurs in the liver.
Q6. Which pigment is mainly responsible for the pale-yellow colour of normal urine?
[Uttar Pradesh Lower Subordinate Preliminary Examination (2008)]
(a) Cytochrome
(b) Urochrome (urobilin)
(c) Haemochrome
(d) Phenolichrome
Answer: (b) Urochrome (urobilin)
Explanation: Normal urine derives its characteristic yellow colour chiefly from urochrome, commonly associated with urobilin pigments produced during haemoglobin breakdown. Darker yellow urine often indicates greater concentration. Abnormal colours may result from food, medication, disease or other pigments.
Q5. Which of the following is NOT a principal function of the kidneys?
[WBCS Preliminary Examination (2006)]
(a) Ultrafiltration
(b) Tubular reabsorption
(c) Tubular secretion
(d) Phagocytosis
Answer: (d) Phagocytosis
Explanation: Kidneys produce urine by glomerular filtration, selective tubular reabsorption and tubular secretion. Phagocytosis is the engulfment of particles by certain cells of the immune system. It is not one of the three primary physiological stages of urine formation.
Q4. Approximately how many litres of urine does a healthy adult ordinarily excrete in 24 hours?
[UPPCS Special Mains General Studies (2004)]
(a) 1.5 litres
(b) 3.0 litres
(c) 6.0 litres
(d) 9.0 litres
Answer: (a) 1.5 litres
Explanation: Average daily urine output in a healthy adult is around 1.5 litres, although roughly one to two litres is a commonly cited range. Fluid intake, temperature, sweating, diet and hormones affect the volume. The kidneys reabsorb most initially filtered water.
Q3. The medical procedure called dialysis is most closely associated with which organ?
[MPPSC Preliminary Examination (2004)]
(a) Liver
(b) Kidney
(c) Eyes
(d) Brain
Answer: (b) Kidney
Explanation: Dialysis is a treatment used when kidneys cannot sufficiently remove waste solutes and excess fluid. In haemodialysis, blood flows past a selectively permeable membrane so unwanted solutes enter the dialysis solution. The method does not fully substitute for kidney hormone production.
Q2. Consider the statements:
(1) filtered blood leaves a kidney through the renal artery;
(2) filtrate passes from Bowman’s capsule into tubules, where glucose is reabsorbed into blood ultimately draining through the renal vein.
Which statement is correct?
[UPSC Civil Services Preliminary Examination (2003)]
(a) Only statement 1
(b) Only statement 2
(c) Both statements
(d) Neither statement
Answer: (b) Only statement 2
Explanation: Statement 1 reverses blood flow: the renal artery supplies the kidney and the renal vein drains it. Statement 2 is essentially correct because tubular glucose reabsorption returns it to peritubular capillaries that ultimately feed the renal venous circulation.
Q1. In which organ of the human body is urea chiefly synthesised?
[WBCS Preliminary Examination (2002)]
(a) Kidneys
(b) Liver
(c) Pancreas
(d) Urinary bladder
Answer: (b) Liver
Explanation: Urea is synthesised in hepatocytes by the urea cycle, which detoxifies ammonia generated during amino-acid metabolism. Once released into blood, urea is transported to the kidneys for excretion. The urinary bladder stores urine but does not synthesise urea.
