Vitamins & Minerals — Set 6

Correct Answer: B. Vitamin D

• **Vitamin D** = Vitamin D is called the 'sunshine vitamin' because the human body synthesises it when UV-B rays from sunlight convert 7-dehydrocholesterol in the skin into Vitamin D3 (Cholecalciferol) — no other vitamin is manufactured this way. • **Dual source** — Vitamin D can be obtained both from sunlight (the primary source for most people) and from foods like fatty fish, egg yolk, and fortified milk, but dietary sources alone are often insufficient without sun exposure. • About 15–20 minutes of midday sunlight on arms and face is enough for fair-skinned individuals to meet their daily Vitamin D requirement. • 💡 Option A (Vitamin C) is wrong because Vitamin C cannot be synthesised by the human body and must come entirely from the diet; Option C (Vitamin K) is wrong because Vitamin K is produced by gut bacteria and obtained from green vegetables, not synthesised by sunlight; Option D (Vitamin A) is wrong because Vitamin A is obtained from food as retinol or beta-carotene and is not made by sun exposure.

Correct Answer: D. Vitamin C

• **Vitamin C** = Scurvy is a disease caused by Vitamin C (Ascorbic Acid) deficiency; without Vitamin C, collagen synthesis fails because the enzymes prolyl hydroxylase and lysyl hydroxylase — which require Vitamin C as a cofactor — cannot cross-link collagen fibres. • **Clinical features** — the breakdown of existing collagen causes bleeding gums, perifollicular haemorrhages, poor wound healing, and loosening of teeth; in severe cases, old scars reopen because collagen is continuously remodelled. • Citrus fruits, guava, amla (Indian gooseberry), and bell peppers are extremely rich sources of Vitamin C that prevent Scurvy. • 💡 Option A (Vitamin B) is wrong because Vitamin B complex deficiencies cause Beriberi, Pellagra, or anaemia, not Scurvy; Option B (Vitamin D) is wrong because Vitamin D deficiency causes Rickets in children and Osteomalacia in adults; Option C (Vitamin A) is wrong because Vitamin A deficiency causes Night blindness and Xerophthalmia.

Correct Answer: A. Vitamin A

• **Vitamin A** = Vitamin A (as 11-cis-retinal) is the chromophore of rhodopsin, the photopigment in rod cells of the retina; rod cells detect low-intensity light, and without adequate retinal, they cannot regenerate rhodopsin fast enough after light exposure, causing Night blindness (Nyctalopia). • **Retinol cycle** — all-trans-retinal released after light absorption must be isomerised back to 11-cis-retinal to reform rhodopsin; this recycling depends on a continuous supply of Vitamin A from the liver. • Night blindness is the earliest and most reversible symptom of Vitamin A deficiency; if untreated it progresses to Xerophthalmia and permanent blindness. • 💡 Option B (Vitamin C) is wrong because Vitamin C deficiency causes Scurvy (gum bleeding, poor wound healing) and does not affect vision; Option C (Vitamin D) is wrong because Vitamin D deficiency affects calcium absorption and bone health, not the retina; Option D (Vitamin B) is wrong because Vitamin B deficiencies affect energy metabolism and nerves, not the visual cycle.

Correct Answer: A. Vitamin C

• **Vitamin C** = Vitamin C (Ascorbic Acid) is water-soluble, meaning it dissolves in water, is transported in blood plasma, and is excreted in urine when consumed in excess — making toxicity rare but also requiring regular daily intake since the body cannot store it. • **Fat-soluble group** — the four fat-soluble vitamins are A, D, E, and K (remembered as ADEK); these are absorbed with dietary fat, stored in adipose tissue and the liver, and can accumulate to toxic levels if over-consumed, unlike Vitamin C. • All B vitamins are also water-soluble, making Vitamin C part of the water-soluble group alongside the B complex. • 💡 Option B (Vitamin D) is wrong because Vitamin D is fat-soluble and is stored in adipose tissue; Option C (Vitamin A) is wrong because Vitamin A is fat-soluble and stored in the liver; Option D (Vitamin E) is wrong because Vitamin E (Tocopherol) is fat-soluble and stored in cell membranes and adipose tissue.

Correct Answer: B. Iron

• **Iron** = Haemoglobin is made of four globin protein chains, each containing a haem group with an iron (Fe²⁺) atom at its centre; this iron atom reversibly binds one oxygen molecule, allowing haemoglobin to carry four oxygen molecules per molecule — iron is structurally irreplaceable in this function. • **Ferritin storage** — the body stores iron in ferritin and haemosiderin proteins in the liver, spleen, and bone marrow; when dietary iron is insufficient, these stores are depleted first before haemoglobin synthesis is affected, eventually causing microcytic hypochromic anaemia. • Dietary iron comes in two forms: haem iron (from meat, highly absorbed) and non-haem iron (from plant foods, less absorbed but enhanced by Vitamin C). • 💡 Option A (Sodium) is wrong because sodium regulates fluid balance and generates nerve impulses, not haemoglobin structure; Option C (Calcium) is wrong because calcium builds bone and triggers muscle contraction, but is not part of the haemoglobin molecule; Option D (Iodine) is wrong because iodine is incorporated into thyroid hormones, not haemoglobin.

Correct Answer: B. Vitamin D

• **Vitamin D** = Rickets is a childhood bone disease caused by Vitamin D deficiency; without Vitamin D, calcium and phosphate absorption in the intestine is inadequate, so the bone matrix (osteoid) is produced normally but fails to mineralise, resulting in soft, weak bones. • **Characteristic signs** — Rickets causes bowed legs (genu varum), widening of the wrists and ankles (rachitic rosary at costochondral junctions), delayed tooth eruption, and in severe cases a pigeon chest deformity; these are all due to undermineralised, deformable bones. • Sunlight exposure, consumption of fortified milk and fatty fish, and Vitamin D supplements effectively prevent and treat Rickets. • 💡 Option A (Vitamin B) is wrong because Vitamin B1 deficiency causes Beriberi, not Rickets; Option C (Vitamin A) is wrong because Vitamin A deficiency causes Night blindness and Xerophthalmia; Option D (Vitamin C) is wrong because Vitamin C deficiency causes Scurvy with bleeding gums and joint pain.

Correct Answer: A. Iodine

• **Iodine** = Goitre is an abnormal enlargement of the thyroid gland caused primarily by iodine deficiency; the thyroid gland requires iodine to synthesise the hormones T3 and T4, and when iodine is scarce the pituitary releases excess TSH to stimulate greater uptake, causing the gland to hypertrophy. • **Endemic Goitre** — regions far from the sea (inland mountains, plains) tend to have iodine-poor soil and water; historically, goitre was widespread in such areas before the introduction of iodised salt as a preventive public health measure. • Beyond Goitre, severe iodine deficiency during pregnancy can cause Cretinism — irreversible intellectual disability and stunted growth in the child. • 💡 Option B (Calcium) is wrong because calcium deficiency causes Osteoporosis and Rickets, not thyroid enlargement; Option C (Zinc) is wrong because zinc deficiency impairs immunity and wound healing, not thyroid size; Option D (Iron) is wrong because iron deficiency causes anaemia, not Goitre.

Correct Answer: B. Vitamin K

• **Vitamin K** = Vitamin K is the essential cofactor for the enzyme gamma-glutamyl carboxylase, which activates the vitamin K-dependent clotting factors: II (Prothrombin), VII, IX, and X; without Vitamin K, these zymogens remain inactive and blood clotting cannot proceed normally. • **Warfarin mechanism** — the anticoagulant drug Warfarin works precisely by antagonising Vitamin K, preventing the recycling of Vitamin K epoxide back to its active form; this reduces clotting factor activity and prevents dangerous blood clots. • Vitamin K also activates osteocalcin, a protein that binds calcium in bone, making it important for both clotting and bone health. • 💡 Option A (Vitamin E) is wrong because Vitamin E is an antioxidant that protects cell membranes from lipid peroxidation and actually mildly inhibits platelet aggregation; Option C (Vitamin C) is wrong because Vitamin C is vital for collagen synthesis but does not activate coagulation factors; Option D (Vitamin A) is wrong because Vitamin A supports vision, immune function, and cell differentiation, not blood coagulation.

Correct Answer: A. Vitamin B1

• **Vitamin B1** = Beri-beri (from Sinhalese: 'I cannot, I cannot', reflecting extreme weakness) is caused by Thiamine (Vitamin B1) deficiency; Thiamine as TPP is indispensable for pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase in the Krebs cycle — without it, cellular energy production fails. • **Two clinical forms** — Dry Beri-beri affects the peripheral nervous system, causing symmetrical motor and sensory neuropathy with muscle wasting; Wet Beri-beri affects the cardiovascular system, causing high-output cardiac failure with oedema; both result from the same Thiamine deficiency. • Beri-beri was historically common in populations eating polished white rice, which lacks the Thiamine-rich bran layer removed during milling. • 💡 Option B (Vitamin B2) is wrong because Riboflavin (B2) deficiency causes cheilosis (cracked lip corners) and corneal vascularisation, not Beri-beri; Option C (Vitamin B12) is wrong because B12 deficiency causes megaloblastic anaemia and nerve degeneration; Option D (Vitamin B6) is wrong because Pyridoxine (B6) deficiency causes dermatitis, peripheral neuropathy, and microcytic anaemia, not the cardiovascular-neural syndrome of Beri-beri.

Correct Answer: C. Calcium

• **Calcium** = Calcium phosphate (as hydroxyapatite crystals) constitutes about 65–70% of bone dry weight and 96% of tooth enamel; it is the mineral framework that gives bones their compressive strength and teeth their hardness to withstand chewing forces. • **Bone remodelling balance** — osteoblasts continuously deposit calcium into new bone matrix while osteoclasts resorb it; adequate dietary calcium intake, aided by Vitamin D for absorption and Vitamin K for mineralisation, maintains a positive balance that supports strong bone density throughout life. • Peak bone mass is achieved around age 25–30; calcium intake during childhood and adolescence is critical to maximise this peak and reduce future fracture risk. • 💡 Option A (Iodine) is wrong because iodine is required for thyroid hormone synthesis and has no structural role in bone or teeth; Option B (Iron) is wrong because iron is the central component of haemoglobin and myoglobin, not bone mineral; Option D (Sodium) is wrong because sodium regulates fluid and electrolyte balance but does not contribute to the mineral matrix of bone or enamel.