BPSC 70th CCE Re-exam Prelims General Studies · Question 40 of 142

Correct — D, None of these. Vitamins are sorted into exactly two groups by the solvent in which they dissolve, and the division is absolute: the FAT-soluble vitamins are A, D, E and K, and the WATER-soluble vitamins are the eight B-complex vitamins together with vitamin C. All three substantive options on this page — Vitamin K, Vitamin A and Vitamin D — belong to the fat-soluble group, so not one of them answers the question and the escape option is the only response left. That is the whole logic of the item, and it is worth seeing why the three were chosen: they are A, D and K, which is three-quarters of the fat-soluble set, with only vitamin E left out. The distinction is not a filing convenience. Fat-soluble vitamins are absorbed with dietary fat, travel in chylomicrons through the lymphatic system, and are stored in the liver and in adipose tissue, so they need not be eaten daily and, taken in excess, they accumulate — hypervitaminosis A and hypervitaminosis D are real toxic states. Water-soluble vitamins are absorbed directly into the portal blood, are held in the body only in small amounts, and any surplus is filtered out by the kidneys and lost in urine, so they must be supplied regularly and are very hard to overdose on. Vitamin B12 is the one partial exception: it is water-soluble but the liver stores enough of it to last several years. Two of the three named options have their own giveaway properties: vitamin D is the vitamin the skin manufactures itself from a cholesterol precursor on exposure to ultraviolet B, and vitamin K is largely supplied by bacteria in the large intestine and is required for the liver to make prothrombin and the other clotting factors — neither behaviour is possible for a vitamin that is simply washed out in urine.

• (a)Vitamin K — Fat-soluble. Vitamin K — phylloquinone from green leafy vegetables and menaquinone from gut bacteria — is the coagulation vitamin, needed for the liver to synthesise prothrombin and the other vitamin-K-dependent clotting factors. Its deficiency shows as delayed clotting and bleeding, which is why newborns are routinely given a vitamin K injection.
• (b)Vitamin A — Fat-soluble, and the classic example of a stored vitamin — the liver holds enough to last months, which is why a single high-dose supplement can protect a child for six months. Deficiency causes night blindness and, in its severe form, xerophthalmia; excess causes hypervitaminosis A, a genuine toxicity that would be impossible if the vitamin were flushed out in urine.
• (c)Vitamin D — Fat-soluble, and strictly a prohormone rather than a dietary essential in the ordinary sense — the skin makes cholecalciferol from 7-dehydrocholesterol under ultraviolet B light. Its deficiency causes rickets in children and osteomalacia in adults; because it is stored rather than excreted, excess intake causes hypercalcaemia.

A vitamin is an organic compound the body needs in small quantity but cannot synthesise in adequate amount, so it must come from the diet. Thirteen are recognised for humans, and the standard classification splits them by solubility because solubility governs everything else about how the body handles them — absorption, transport, storage, excretion and the shape of both deficiency and toxicity. The four fat-soluble vitamins, A, D, E and K, ride with dietary lipids, are stored, and can therefore be both hoarded and overdosed. The nine water-soluble vitamins — B1 thiamine, B2 riboflavin, B3 niacin, B5 pantothenic acid, B6 pyridoxine, B7 biotin, B9 folate, B12 cobalamin and C ascorbic acid — dissolve in plasma, are turned over quickly and are lost in urine, which is why their deficiency diseases appear comparatively fast on a poor diet and why cooking water can strip them out of food.

The one thing to memorise is the four-letter set ADEK: those are the fat-soluble vitamins, and everything else on the list is water-soluble. Run any option against that set and the question answers itself in a second. The structural lesson is more useful still. 'None of these' is correct only when every named option can be shown to fail, and here that test is easy to apply because the three named options are homogeneous — all from the same class, and that class is the wrong one. When an examiner offers three items that plainly belong to one family and asks for a property of the other family, the escape option is usually not a trap but the intended answer. Contrast this with a question that mixes classes, where at least one option will normally survive. Do not carry that observation any further than the individual question, though: it is a reason to check the options on this page, not a rule about how often the Commission keys 'None of these'.

• Fat-soluble vitamins: A, D, E and K — absorbed with dietary fat, transported in chylomicrons via the lymph, and stored in the liver and adipose tissue.
• Water-soluble vitamins: the eight B-complex vitamins (B1, B2, B3, B5, B6, B7, B9, B12) and vitamin C — absorbed into portal blood and excreted in urine when in excess.
• Vitamin B12 is the partial exception to the water-soluble rule: it is stored in the liver in amounts sufficient for several years.
• Vitamin D is synthesised in the skin from 7-dehydrocholesterol on exposure to ultraviolet B; vitamin K is largely supplied by bacteria of the large intestine.
• Deficiency signatures to hold together: A — night blindness and xerophthalmia; D — rickets and osteomalacia; K — defective blood clotting; C — scurvy; B1 — beriberi; B3 — pellagra.

• Calling vitamin K water-soluble because it is associated with green leafy vegetables and with gut bacteria. Its source has nothing to do with its solubility.
• Treating 'None of these' as a decoy on principle and forcing one of the three named vitamins into the answer.
• Confusing vitamin D deficiency with calcium deficiency. Vitamin D deficiency causes rickets because calcium cannot be absorbed without it, but the vitamin is the one being asked about.

BPSC asks vitamins as single-line recall — which vitamin is water-soluble, which deficiency causes which disease, which vitamin the skin synthesises — and is willing to make the whole question turn on a class rather than on a name. UPSC asks the same syllabus as a pairs or statement question, typically matching a vitamin to its deficiency disease and inserting one wrong pair, as in its 2014 item where Vitamin E was falsely paired with night blindness.

• practice — not a real PYQ

  Which one of the following vitamins is synthesised in the human skin on exposure to sunlight ?

  • (a)Vitamin A
  • (b)Vitamin B12
  • (c)Vitamin C
  • (d)Vitamin D

  Answer(d) Vitamin D — ultraviolet B radiation converts 7-dehydrocholesterol in the skin into cholecalciferol, which the liver and kidney then activate. This is why vitamin D deficiency is a disorder of sunlight exposure as much as of diet.

• practice — not a real PYQ

  Deficiency of which vitamin impairs blood clotting ?

  • (a)Vitamin C
  • (b)Vitamin K
  • (c)Vitamin B1
  • (d)Vitamin E

  Answer(b) Vitamin K — it is required for the liver to synthesise prothrombin and the other vitamin-K-dependent clotting factors. Vitamin C deficiency gives scurvy and B1 deficiency gives beriberi, neither of which is primarily a clotting disorder.