Vitamins & Minerals — Set 2

Correct Answer: C. Vitamin C

• **Vitamin C** = The chemical name 'ascorbic acid' comes from 'a-scorbic' meaning 'anti-scurvy', reflecting its discovery as the dietary factor that prevents and cures Scurvy; the molecule is a six-carbon lactone structurally similar to glucose. • **Powerful antioxidant** — Vitamin C donates electrons to neutralise free radicals, regenerates Vitamin E from its oxidised form, and is essential for the synthesis of collagen, carnitine, and certain neurotransmitters like norepinephrine. • Humans, guinea pigs, and a few other species cannot synthesise Vitamin C internally because they lack the enzyme L-gulonolactone oxidase, making dietary intake mandatory. • 💡 Option A (Vitamin A) is wrong because its chemical name is retinol (active form) or beta-carotene (provitamin form); Option B (Vitamin D) is wrong because its active form is calcitriol (1,25-dihydroxycholecalciferol); Option D (Vitamin B) is wrong because the B-complex group has different chemical names — thiamine (B1), riboflavin (B2), niacin (B3), etc.

Correct Answer: A. Vitamin B1

• **Vitamin B1 (Thiamine)** = Thiamine is an essential coenzyme in carbohydrate metabolism, specifically for the enzyme pyruvate dehydrogenase that converts pyruvate to acetyl-CoA; its deficiency disrupts energy production in nerve and cardiac muscle cells, causing Beriberi. • **Two clinical forms** — Wet Beriberi predominantly affects the cardiovascular system (enlarged heart, oedema, heart failure), while Dry Beriberi affects the peripheral nervous system (muscle weakness, paralysis, wasting); both occur from the same thiamine deficiency. • Beriberi was historically rampant in Asian populations that subsisted on polished (white) rice, from which the thiamine-rich bran is removed during milling. • 💡 Option B (Vitamin B2/Riboflavin) is wrong because its deficiency causes Ariboflavinosis — cracked lips, mouth sores, and eye inflammation; Option C (Vitamin B6/Pyridoxine) is wrong because its deficiency causes peripheral neuropathy and mild anemia; Option D (Vitamin B12) is wrong because its deficiency causes Pernicious Anemia and neurological degeneration.

Correct Answer: A. Vitamin B12

• **Vitamin B12 (Cobalamin)** = Vitamin B12 is the only vitamin that contains a metal ion — cobalt — at the centre of its corrin ring structure, which is why it is also called cobalamin; this cobalt atom is essential for its role as a coenzyme in DNA synthesis and methylation reactions. • **Unique biological source** — Vitamin B12 is synthesised exclusively by certain bacteria and archaea; animals obtain it by eating other animals or through gut bacterial synthesis, making animal products (meat, fish, dairy, eggs) the only reliable dietary source for humans. • Strict vegetarians and vegans are at high risk of B12 deficiency and must supplement, since plant foods contain no B12 naturally. • 💡 Option B (Vitamin B2/Riboflavin) is wrong because it contains isoalloxazine rings with no metal ion; Option C (Vitamin B6/Pyridoxine) is wrong because it is a pyridine derivative with no metal in its structure; Option D (Vitamin B1/Thiamine) is wrong because it is a thiazolium compound containing only carbon, hydrogen, nitrogen, oxygen, and sulphur.

Correct Answer: C. Vitamin K

• **Vitamin K** = Vitamin K is one of four fat-soluble vitamins (A, D, E, K); it dissolves in fats and oils, requires dietary fat for absorption in the small intestine via chylomicrons, and is stored in the liver and fatty tissues. • **Two natural forms** — Vitamin K1 (phylloquinone) is found in green leafy vegetables and is the primary dietary form, while Vitamin K2 (menaquinone) is produced by gut bacteria and found in fermented foods like natto. • Fat-soluble vitamins accumulate in the body, so excessive intake of Vitamins A and D can reach toxic levels — a risk that does not apply to water-soluble vitamins which are excreted in urine. • 💡 Option A (Vitamin B12) is wrong because it is water-soluble and is stored in the liver only in relatively small quantities; Option B (Vitamin B) is wrong because the entire B-complex family is water-soluble; Option D (Vitamin C) is wrong because it is the classic water-soluble antioxidant vitamin excreted when consumed in excess.

Correct Answer: A. Vitamin B12

• **Vitamin B12** = Pernicious anemia is specifically caused by Vitamin B12 deficiency arising from a lack of 'intrinsic factor' — a glycoprotein secreted by stomach parietal cells; without intrinsic factor, B12 cannot be absorbed in the ileum, leading to impaired DNA synthesis, abnormally large red blood cells (megaloblastic anemia), and neurological damage. • **Autoimmune mechanism** — in classic pernicious anemia, the immune system destroys parietal cells or blocks intrinsic factor; this distinguishes it from dietary B12 deficiency, which is more common in vegans. • The name 'pernicious' (meaning deadly) was coined before B12 was isolated; it was fatal until liver extract therapy was developed in 1926, earning the Nobel Prize in Physiology or Medicine. • 💡 Option B (Vitamin D) is wrong because its deficiency causes Rickets (children) and Osteomalacia (adults), affecting bone mineralisation; Option C (Vitamin B1/Thiamine) is wrong because its deficiency causes Beriberi; Option D (Vitamin C) is wrong because its deficiency causes Scurvy.

Correct Answer: A. Sodium

• **Sodium** = Sodium (Na⁺) is the dominant extracellular cation and the primary determinant of extracellular fluid volume; it regulates osmotic pressure and water distribution between blood, interstitial fluid, and cells through the sodium-potassium ATPase pump and osmosis. • **Blood pressure link** — high sodium intake causes water retention which increases blood volume and blood pressure; this is why low-sodium diets are prescribed for hypertension and heart failure patients. • The kidney's renin-angiotensin-aldosterone system precisely regulates sodium reabsorption to maintain fluid balance; aldosterone signals the kidney to retain sodium and excrete potassium. • 💡 Option B (Iodine) is wrong because iodine's sole function is the synthesis of thyroid hormones; it has no role in fluid balance; Option C (Fluorine) is wrong because fluoride's primary role is in tooth enamel hardening; Option D (Iron) is wrong because iron functions in oxygen transport via haemoglobin and cellular energy production, not fluid balance.

Correct Answer: A. Vitamin D

• **Vitamin D** = Vitamin D deficiency in children causes Rickets because Vitamin D (as calcitriol) is essential for the intestinal absorption of calcium and phosphate; without adequate Vitamin D, calcium cannot mineralise the growing bone matrix (osteoid), leading to soft, weak, deformed bones — bowed legs, knock knees, and a rachitic rosary on the chest. • **Adult equivalent** — the same deficiency in adults causes Osteomalacia (softening of bones) rather than Rickets because adult bones are already fully formed; both conditions involve defective mineralisation of bone. • In industrialised regions, Rickets has re-emerged due to indoor lifestyles, sunscreen use, and prolonged exclusive breastfeeding without supplementation, since breast milk is low in Vitamin D. • 💡 Option B (Vitamin B) is wrong because B-complex deficiencies cause neurological and metabolic disorders, not bone deformity; Option C (Vitamin A) is wrong because its deficiency causes Night Blindness and Xerophthalmia; Option D (Vitamin C) is wrong because its deficiency causes Scurvy, characterised by bleeding and connective tissue breakdown, not skeletal deformity.

Correct Answer: B. Vitamin E

• **Vitamin E** = The chemical name 'tocopherol' is derived from Greek — 'tokos' (childbirth) and 'phero' (to carry) — reflecting its early discovery as a factor necessary for normal reproduction in rats; the active form in the body is alpha-tocopherol, the most biologically potent of eight natural tocopherol and tocotrienol forms. • **Primary fat-soluble antioxidant** — Vitamin E protects polyunsaturated fatty acids in cell membranes from oxidative damage by free radicals; it works in tandem with Vitamin C, which regenerates the oxidised form of Vitamin E back to its active state. • Rich dietary sources include vegetable oils (sunflower, wheat germ), nuts, seeds, and avocados; deficiency is rare but causes haemolytic anemia and neurological symptoms in severe cases. • 💡 Option A (Vitamin K) is wrong because its chemical names are phylloquinone (K1) and menaquinone (K2); Option C (Vitamin A) is wrong because its chemical name is retinol; Option D (Vitamin D) is wrong because its active form is calcitriol (1,25-dihydroxyvitamin D3).

Correct Answer: D. Iron

• **Iron** = Each haemoglobin molecule contains four haem groups, and at the centre of each haem group sits a single Fe²⁺ (ferrous) iron ion; this iron atom reversibly binds one molecule of oxygen, allowing haemoglobin to carry up to four oxygen molecules from the lungs to body tissues. • **Oxidation state matters** — iron must remain in the Fe²⁺ (ferrous) state to bind oxygen; if oxidised to Fe³⁺ (ferric), it forms methaemoglobin which cannot carry oxygen and causes methaemoglobinaemia. • Myoglobin, the oxygen-storage protein in muscle tissue, also has a single haem group with a central iron atom, explaining why iron-deficiency anemia causes both low blood oxygen and muscle fatigue. • 💡 Option A (Copper) is wrong because copper is the central metal in haemocyanin — the oxygen-carrying pigment in molluscs and arthropods, not in human haemoglobin; Option B (Magnesium) is wrong because magnesium occupies the centre of the chlorophyll molecule in plants, not haemoglobin; Option C (Zinc) is wrong because zinc is vital for enzyme function and immune response but is not part of the haem group.

Correct Answer: C. Niacin

• **Niacin (Vitamin B3)** = Niacin deficiency causes Pellagra, classically described by the '4 Ds': Dermatitis (sun-sensitive skin rash in a necklace pattern), Diarrhoea, Dementia, and Death if untreated; niacin is essential for NAD⁺ and NADP⁺ coenzymes involved in over 400 metabolic reactions. • **Maize connection** — Pellagra was epidemic in communities that relied heavily on maize as a staple food; maize niacin is 'bound' in a form unavailable to humans, and maize also lacks the amino acid tryptophan from which the body can synthesise niacin. • Pellagra was a major public health problem in the American South and parts of Africa in the 19th–20th centuries; it was virtually eliminated after niacin was identified and food fortification began. • 💡 Option A (Thiamine/B1) is wrong because its deficiency causes Beriberi; Option B (Pyridoxine/B6) is wrong because its deficiency causes peripheral neuropathy and mild anemia; Option D (Riboflavin/B2) is wrong because its deficiency causes Ariboflavinosis — angular stomatitis, cheilosis, and glossitis.