Vitamins & Minerals — Set 4

Correct Answer: A. Calcium

• **Calcium** = Calcium is the primary mineral that gives bones their density and strength; a prolonged deficiency causes bones to become porous and brittle, a condition called Osteoporosis. • **Bone remodelling** — the body continuously deposits and reabsorbs calcium from bone; when dietary intake is too low, more is reabsorbed than deposited, weakening the skeleton over time. • Dairy products, leafy greens, and fortified foods are rich dietary sources of calcium. • 💡 Option B (Iron) is wrong because iron deficiency causes anaemia, not brittle bones; Option C (Copper) is wrong because copper deficiency is rare and mainly affects connective tissue; Option D (Zinc) is wrong because zinc deficiency impairs immune function and wound healing, not bone mineral density.

Correct Answer: D. Vitamin A

• **Vitamin A** = Golden rice is a genetically engineered variety of rice that produces beta-carotene, a precursor that the body converts into Vitamin A, addressing deficiency in populations dependent on rice. • **Beta-carotene pathway** — the golden colour comes from carotenoid pigments inserted via genes from daffodil and a soil bacterium; these pigments are converted to retinol (Vitamin A) in the intestine. • Vitamin A deficiency is a leading cause of preventable childhood blindness in developing countries, which golden rice was designed to combat. • 💡 Option A (Vitamin B) is wrong because rice already contains B vitamins naturally and golden rice was engineered specifically for Vitamin A; Option B (Vitamin D) is wrong because Vitamin D is not synthesised by plants; Option C (Vitamin C) is wrong because Vitamin C is abundant in fruits and vegetables, not the target nutrient for golden rice.

Correct Answer: D. Thiamine

• **Thiamine** = Thiamine is the IUPAC-recognised chemical name for Vitamin B1; it contains a pyrimidine ring and a thiazole ring joined by a methylene bridge, giving it its unique structure. • **Coenzyme role** — Thiamine in its active form (Thiamine pyrophosphate, TPP) is essential for carbohydrate metabolism, particularly the pyruvate dehydrogenase reaction that links glycolysis to the Krebs cycle. • Deficiency of Thiamine causes Beri-beri, which damages the nervous and cardiovascular systems. • 💡 Option A (Calciferol) is wrong because Calciferol is the chemical name for Vitamin D; Option B (Riboflavin) is wrong because Riboflavin is the chemical name for Vitamin B2; Option C (Niacin) is wrong because Niacin is the chemical name for Vitamin B3.

Correct Answer: C. Cobalt

• **Cobalt** = Vitamin B12 (Cyanocobalamin) contains a cobalt ion at the centre of its corrin ring, making cobalt the only metal ion that is an intrinsic part of a vitamin molecule in human nutrition. • **Corrin ring** — the corrin ring in B12 is similar to the porphyrin ring in haemoglobin, but the central atom is cobalt instead of iron; this cobalt is essential for B12's role in DNA synthesis and nerve maintenance. • Vitamin B12 is unique among vitamins because it is found almost exclusively in animal-derived foods. • 💡 Option A (Iron) is wrong because iron is the central atom of haemoglobin and myoglobin, not B12; Option B (Zinc) is wrong because zinc is a cofactor for many enzymes but is not part of any vitamin structure; Option D (Magnesium) is wrong because magnesium is the central atom of chlorophyll in plants, not of Vitamin B12.

Correct Answer: C. Vitamin D

• **Vitamin D** = When UV-B radiation from sunlight strikes skin, it converts 7-dehydrocholesterol (a cholesterol derivative) into Vitamin D3 (Cholecalciferol), making sunlight the most efficient natural source of this vitamin. • **Activation pathway** — the skin-produced Vitamin D3 is biologically inactive; it is first hydroxylated in the liver to 25-hydroxyvitamin D, then again in the kidneys to the active form 1,25-dihydroxyvitamin D (Calcitriol), which regulates calcium absorption. • Vitamin D deficiency causes Rickets in children and Osteomalacia in adults. • 💡 Option A (Vitamin E) is wrong because Vitamin E is a dietary antioxidant obtained from plant oils and nuts, not synthesised by sunlight; Option B (Vitamin A) is wrong because Vitamin A is obtained from food as retinol or beta-carotene; Option D (Vitamin K) is wrong because Vitamin K is produced by gut bacteria and obtained from leafy greens, not from UV radiation.

Correct Answer: B. Difficulty in blood clotting

• **Difficulty in blood clotting** = Vitamin K is essential for activating clotting factors II (Prothrombin), VII, IX, and X in the coagulation cascade; without Vitamin K these factors remain inactive and blood cannot clot properly. • **Carboxylation mechanism** — Vitamin K acts as a cofactor for the enzyme gamma-glutamyl carboxylase, which adds carboxyl groups to clotting proteins, enabling them to bind calcium ions needed to form a clot. • Newborns are routinely given Vitamin K injections at birth because they lack gut bacteria to produce it and breast milk is a poor source. • 💡 Option A (Rickets) is wrong because Rickets is caused by Vitamin D deficiency, not Vitamin K; Option C (Night blindness) is wrong because Night blindness results from Vitamin A deficiency; Option D (Beri-beri) is wrong because Beri-beri is caused by Vitamin B1 (Thiamine) deficiency.

Correct Answer: A. Iron

• **Iron** = Iron is the central atom of the haem group in haemoglobin, the protein inside red blood cells that carries oxygen; without sufficient iron, the body cannot produce functional haemoglobin and red blood cell production falls — causing iron-deficiency anaemia. • **Erythropoiesis dependency** — in the bone marrow, developing red blood cell precursors (erythroblasts) require iron to synthesise haemoglobin; iron shortage slows this process and produces smaller, paler cells. • Iron is also a component of myoglobin (oxygen storage in muscles) and cytochromes (electron transport chain). • 💡 Option B (Iodine) is wrong because iodine is required for thyroid hormone synthesis, not red blood cell production; Option C (Sodium) is wrong because sodium regulates fluid balance and nerve signalling; Option D (Calcium) is wrong because calcium is critical for bone structure and muscle contraction, not haemoglobin synthesis.

Correct Answer: C. Vitamin D

• **Vitamin D** = The chemical name Calciferol refers to Vitamin D; the name derives from "calcium" and "-ferol" (sterol), reflecting its primary role in regulating calcium and phosphate absorption in the intestine. • **Two main forms** — Vitamin D2 (Ergocalciferol) is found in plants and fungi, while Vitamin D3 (Cholecalciferol) is synthesised in human skin and found in animal foods; both are collectively called Calciferol. • Vitamin D is the only vitamin the human body can manufacture itself through skin exposure to sunlight. • 💡 Option A (Vitamin A) is wrong because Vitamin A is chemically known as Retinol; Option B (Vitamin B) is wrong because Vitamin B is a complex of several water-soluble vitamins with different chemical names (Thiamine, Riboflavin, Niacin, etc.); Option D (Vitamin C) is wrong because Vitamin C is chemically known as Ascorbic Acid.

Correct Answer: D. Iodine

• **Iodine** = Thyroxine (T4) is a thyroid hormone that contains four iodine atoms per molecule; iodine is literally incorporated into the amino acid tyrosine to form the hormone, making it biochemically indispensable for thyroid function. • **Synthesis pathway** — in thyroid follicular cells, iodide ions are oxidised and attached to tyrosine residues on the protein thyroglobulin to form mono- and diiodotyrosine, which are then coupled to produce T3 and T4. • Iodine deficiency causes the thyroid gland to enlarge (Goitre) as it attempts to trap more iodine from the blood. • 💡 Option A (Magnesium) is wrong because magnesium is a cofactor for hundreds of enzymes but is not part of any hormone structure; Option B (Iron) is wrong because iron is central to haemoglobin and cytochromes, not thyroid hormones; Option C (Zinc) is wrong because zinc is important for immune function and enzyme activity, not thyroid hormone composition.

Correct Answer: C. Vitamin K

• **Vitamin K** = Vitamin K1 (Phylloquinone) is synthesised by plants as part of the photosynthetic electron transport chain and accumulates in chloroplast-rich leafy green vegetables like spinach, kale, and broccoli. • **Two dietary forms** — Vitamin K1 (Phylloquinone) from plants is the main dietary form and is directly used for blood clotting; Vitamin K2 (Menaquinone) is produced by gut bacteria and also plays a role in bone metabolism. • Vitamin K is fat-soluble, so consuming it with a small amount of fat improves absorption. • 💡 Option A (Vitamin D) is wrong because Vitamin D is made in skin from sunlight and is found in animal foods like fish and eggs, not primarily in leafy greens; Option B (Vitamin B12) is wrong because B12 is found almost exclusively in animal-derived foods and is absent in leafy vegetables; Option D (Vitamin D2) is wrong because Vitamin D2 (Ergocalciferol) is found in mushrooms and fungi exposed to UV, not in leafy greens.