Given below are two statements, one labelled as Assertion (A) and the other as Reason (R). Assertion (A) : Most of the vitamins are not synthesised in human body. Reason (R) : Human organs synthesise only essential micronutrients. Select the correct answer from the codes given below : Codes :
- (a)Both (A) and (R) are true and (R) is the correct explanation of (A)
- (b)Both (A) and (R) are true but (R) is not the correct explanation of (A)
- (c)(A) is true, but (R) is false
- (d)(A) is false but (R) is true
Correct — C, (A) is true but (R) is false. The Assertion is true almost by definition: a vitamin is an organic micronutrient that the human body cannot manufacture in adequate amounts, so it has to be supplied by the diet. A handful of partial exceptions exist — vitamin D is made in the skin from a cholesterol derivative under ultraviolet light, some niacin can be built from the amino acid tryptophan, and gut bacteria produce vitamin K2 and biotin — but for the great majority of vitamins the body has no synthetic route at all. The Reason, however, is false, and it fails in the most instructive way possible: it inverts the meaning of the word 'essential'. In nutrition, a nutrient is called essential precisely because the body CANNOT synthesise it and must obtain it ready-made from food. So saying that human organs 'synthesise only essential micronutrients' states the exact opposite of the truth. Since (A) is true and (R) is false, the code is (c).
- (a)Both (A) and (R) are true and (R) is the correct explanation of (A) — Rejected because the Reason is not true. It claims the body synthesises the essential micronutrients — but 'essential' is the technical label for exactly those nutrients the body cannot make. A false Reason can never be the correct explanation of anything.
- (b)Both (A) and (R) are true but (R) is not the correct explanation of (A) — Also requires the Reason to be true, and it is not. This option is the standard trap for students who sense that the two statements do not fit together but never test the Reason on its own merits.
- (d)(A) is false but (R) is true — This reverses the truth values. The Assertion is the well-established one — most vitamins genuinely are not synthesised in the human body, which is why they must be eaten — while the Reason is the flawed statement.
Nutrition divides nutrients into essential and non-essential, and the dividing line is a chemical one: can human cells build the molecule from what is already available? If they cannot, the nutrient is essential and the diet must supply it — this covers the nine essential amino acids, the essential fatty acids (linoleic and alpha-linolenic acid), the minerals, and almost all the vitamins. If the body can build it, the nutrient is non-essential, even though it may be vital to life; cholesterol, most fatty acids and eleven of the amino acids fall here. Vitamins were named and hunted down in the early twentieth century precisely because they were traces of something in food that the body could not do without and could not make; Casimir Funk coined the word 'vitamine' in 1912.
Assertion–Reason questions are won by judging the two statements separately before you look at the codes. Read (A): most vitamins are not made in the body — that is the textbook definition, so it is true. Now read (R) on its own, ignoring (A) completely: does the body synthesise essential micronutrients? No — the whole point of the word 'essential' is that it does not. With (A) true and (R) false, only one code survives, and you never have to think about whether one explains the other. The examiner's trap is that (R) sounds authoritative and uses the right vocabulary, so a hurried candidate accepts it and then agonises over options (a) and (b).
- A vitamin is an organic compound needed in small amounts that the body cannot synthesise in sufficient quantity, so it must come from the diet.
- The exceptions are limited: vitamin D is synthesised in the skin from 7-dehydrocholesterol under UV-B sunlight, niacin can be made in part from the amino acid tryptophan, and intestinal bacteria produce vitamin K2 and biotin.
- 'Essential' in nutrition means the body cannot make it — the term applies to nine essential amino acids and to the essential fatty acids linoleic and alpha-linolenic acid.
- Humans, other primates and guinea pigs cannot make vitamin C because the enzyme of the last step, L-gulonolactone oxidase, is non-functional in them, while most other mammals synthesise their own ascorbic acid.
- In an Assertion–Reason question, always settle the truth of each statement independently before asking whether the Reason explains the Assertion.
Assertion true, Reason false — the Reason inverts the definition of an essential nutrient, which gives code (c).
- Accepting a confidently worded Reason without testing it. Here the Reason simply inverts the definition of 'essential'.
- Over-reading the exceptions. Vitamin D, niacin and bacterial vitamin K do not make the Assertion false — the Assertion only claims 'most' vitamins.
- Jumping to option (a) because the two sentences are on the same topic. Same topic is not the same as a correct explanation, and it certainly does not make a false Reason true.
UPPSC is fond of the Assertion–Reason code on vitamins and asked a mirror-image version of this very statement in 2021; UPSC has used the identical structure on essential amino acids and essential fatty acids, where the trap is placed on the Assertion instead.
Assertion (A): Fatty acids should be a part of the balanced human diet. Reason (R): The cells of the human body cannot synthesize any fatty acids.
- (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 the 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
The same question with fatty acids in place of vitamins, and the same code as its answer — a true Assertion about diet paired with a Reason that overstates what the body cannot synthesise.
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
The same concept — what 'essential' means — with the trap moved to the Assertion instead of the Reason. UPSC states the definition of an essential nutrient correctly here; UPPSC inverted it.
Given below are two statements, one is labelled as Assertion (A) and other as Reason (R): Assertion (A): Human body synthesises all the vitamins required by it. Reason (R): Vitamins are essential for proper growth of the body. Select the correct answer using the codes given below.
- (a) Both (A) and (R) are true and (R) is correct explanation of (A)
- (b) Both (A) and (R) are true, but (R) is not 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
The exact mirror image, asked by the same commission two years later — there the false statement is the Assertion ('the body synthesises all the vitamins'), here it is the Reason. One fact, learnt once, answers both.
- practice — not a real PYQ
Which vitamin can be synthesised in the human skin on exposure to sunlight?
- (a)Vitamin D
- (b)Vitamin C
- (c)Vitamin B12
- (d)Vitamin K1
Answer(a) Vitamin D — ultraviolet-B radiation converts 7-dehydrocholesterol in the skin into a vitamin D precursor, which the liver and kidney then activate. It is the main exception to the rule that vitamins must come from food.
- practice — not a real PYQ
In human nutrition, a nutrient is described as 'essential' when
- (a)the body cannot synthesise it and it must be supplied by the diet
- (b)the body synthesises it in large amounts
- (c)it is needed only in trace quantities
- (d)it supplies energy to the body
Answer(a) the body cannot synthesise it and it must be supplied by the diet — the term describes the source of the nutrient, not how much of it is needed or how important it is.