UPSC Prelims 2002 Q148: Science & Technology – Health & Diseases
Assertion (A): Human diet should compulsorily contain Glycerine, Serine and Tyrosine.
Reason (R): Essential amino acids cannot be synthesised in the human 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: (d) A is false but R is true
Explanation
Assertion-Reason: glycine, serine, tyrosine and the human diet
| Statement | Verdict |
|---|---|
| Assertion: the diet must compulsorily contain glycine, serine and tyrosine | False — these are non-essential amino acids made by the body |
| Reason: essential amino acids cannot be synthesised in the body | True |
| Essential amino acids | Valine, leucine, isoleucine, lysine, methionine, threonine, phenylalanine, tryptophan (and histidine) |
| Result | A is false but R is true |
Glycine, serine and tyrosine can be made in the human body, so they need not be taken in the diet. The reason is true: essential amino acids cannot be synthesised and must be eaten. Hence A is false and R is true.
Answer: (d) A is false but R is true.
Why each option is right or wrong
- (a) Incorrect. A is false since these amino acids are non-essential.
- (b) Incorrect. A is false, so both cannot be true.
- (c) Incorrect. R is true; essential amino acids cannot be synthesised.
- (d) CORRECT. A is false and R is true.
Key point
Essential amino acids (9 for adults): his, ile, leu, lys, met, phe, thr, trp, val; tyrosine is made from phenylalanine.
Remember
Essential amino acids must come from food; glycine, serine and tyrosine need not.
Common mistakes
- Treating all amino acids as essential.
- Assuming that tyrosine must be eaten in the diet.
- Reading the reason R as the reason for A.
Exam tip
Glycine and serine are the simplest, non-essential amino acids.
Sources
- NCERT Class XI Biology — Biomolecules
- NCERT Class XII Chemistry — Biomolecules (amino acids: essential and non-essential)