UPSC Prelims 2002 Q141: Science & Technology – Biology
Assertion (A): Drinking of whisky increases the frequency of urination.
Reason (R): Alcohol intake speeds up the secretion of vasopressin in the body.
- (a) Both A and R are individually true and R is the correct explanation of A
- (b) Both A and R are individually true but R is not a correct explanation of A
- (c) A is true but R is false
- (d) A is false but R is true
Answer: (c) A is true but R is false
Explanation
Assertion-Reason: whisky and frequency of urination
| Statement | Verdict |
|---|---|
| Assertion: whisky increases the frequency of urination | True — alcohol is a diuretic |
| Reason: alcohol speeds up the secretion of vasopressin | False — alcohol inhibits vasopressin (ADH) |
| Why | Less ADH means less water reabsorbed in the kidney, so more urine |
| Result | A is true but R is false |
Alcohol suppresses the release of the antidiuretic hormone vasopressin, so the kidneys reabsorb less water and the urine volume rises. The assertion is true, while the reason, which says secretion is speeded up, is false.
Answer: (c) A is true but R is false.
Why each option is right or wrong
- (a) Incorrect. R is false because alcohol inhibits vasopressin, so it cannot explain A.
- (b) Incorrect. R is false, so both cannot be individually true.
- (c) CORRECT. A is true; R is false because alcohol suppresses vasopressin.
- (d) Incorrect. A is true, since alcohol increases urination.
Key point
Vasopressin (ADH): raises water reabsorption in the collecting ducts; diabetes insipidus is its deficiency.
Remember
Alcohol lowers ADH and increases urine output.
Common mistakes
- Thinking alcohol raises ADH secretion.
- Ignoring that the assertion is true.
- Choosing 'R explains A' without checking R.
Exam tip
More urine means less ADH, so R is the wrong way round.
Sources
- NCERT Class XI Biology — Excretory Products and their Elimination
- John E. Hall — Guyton and Hall Textbook of Medical Physiology (Urine Concentration and Dilution; Regulation of Extracellular Fluid Osmolarity and Sodium Concentration)