Nutrition Basics — Set 1

Correct Answer: D. Glucose

• **Glucose** = the sole fuel the brain relies on under normal conditions, supplying energy to neurons for every thought and action. • **Priority organ** — the brain consumes roughly 120 g of glucose per day, accounting for about 20% of total body energy use despite its small size. • Neurons cannot store glucose, so a steady blood-sugar supply is critical for concentration and consciousness. • 💡 Option A (Minerals) is wrong because minerals regulate enzymes and electrolytes but release no energy at all; Option B (Proteins) is wrong because proteins are dismantled for tissue repair first and are a poor, slow emergency fuel; Option C (Fats) is wrong because fatty acids cannot cross the blood-brain barrier in significant amounts under normal conditions.

Correct Answer: A. Assisting in bowel movement

• **Roughage (dietary fiber)** = adds indigestible bulk to intestinal contents, stimulating peristaltic muscle contractions that push waste through the colon. • **Gut health** — feeds beneficial bacteria (prebiotic effect), softens stools, and reduces transit time, preventing constipation and diverticular disease. • Adequate fiber intake (25–38 g/day) is also linked to lower cholesterol and reduced risk of colorectal cancer. • 💡 Option B (Providing instant energy) is wrong because fiber cannot be broken down by human digestive enzymes and yields essentially no calories; Option C (Repairing damaged tissues) is wrong because that requires amino acids from proteins; Option D (Building strong muscles) is wrong because muscle synthesis depends on dietary protein and resistance exercise.

Correct Answer: D. Vitamin K

• **Vitamin K** = acts as a cofactor for the enzyme gamma-glutamyl carboxylase, which activates prothrombin and six other clotting factors in the coagulation cascade. • **Two forms** — K1 (phylloquinone) from leafy greens handles clotting; K2 (menaquinone) from fermented foods also supports bone metabolism. • Newborns receive a vitamin K injection at birth because breast milk is low in it and gut flora are not yet established. • 💡 Option A (Vitamin A) is wrong because it governs vision and epithelial integrity, not clot formation; Option B (Vitamin C) is wrong because it supports collagen synthesis and immune function but does not activate clotting factors; Option C (Vitamin D) is wrong because it regulates calcium absorption for bones, not coagulation proteins.

Correct Answer: D. Iodine

• **Iodine** = directly incorporated into the thyroxine (T4) and triiodothyronine (T3) molecules, which regulate the body's basal metabolic rate. • **Goiter and cretinism** — chronic iodine deficiency enlarges the thyroid gland (goiter) and causes cretinism (irreversible intellectual disability) in infants born to deficient mothers. • Iodized salt introduced in the 20th century eliminated endemic goiter in most countries. • 💡 Option A (Magnesium) is wrong because it activates ATP-dependent enzymes but is not part of thyroid hormone; Option B (Iron) is wrong because it forms the heme core of hemoglobin, not thyroid hormone; Option C (Calcium) is wrong because it provides skeletal strength and muscle signaling, not thyroid hormone structure.

Correct Answer: C. Protein supplementation

• **Casein** = a slow-digesting phosphoprotein making up ~80% of milk protein, delivering a sustained supply of essential amino acids for tissue growth and repair. • **Micellar structure** — casein forms protein micelles in milk that curdle in the stomach, slowing gastric emptying and prolonging amino acid release over 5–7 hours. • This slow-release property makes casein especially valuable for overnight muscle recovery in athletes. • 💡 Option A (Enzymatic action) is wrong because casein is a storage protein, not a functional enzyme; Option B (Structural support) is wrong because collagen and elastin provide connective-tissue structure; Option D (Energy storage) is wrong because energy is stored in adipose tissue as triglycerides and in muscle as glycogen.

Correct Answer: D. Calcium

• **Calcium** = the most abundant mineral in the body, required at 1,000–1,200 mg per day — far more than trace minerals — to build bones, teeth, and support muscle contraction. • **Beyond bones** — calcium also triggers neurotransmitter release at synapses and is essential for heart muscle rhythmicity. • Macro-minerals (calcium, phosphorus, magnesium, sodium, potassium, chloride, sulfur) are all needed in quantities exceeding 100 mg/day. • 💡 Option A (Iron) is wrong because it is a trace/micro-mineral needed in only 8–18 mg per day; Option B (Copper) is wrong because it is needed in microgram amounts (~0.9 mg/day); Option C (Zinc) is wrong because it is also a trace mineral required at just 8–11 mg per day.

Correct Answer: C. Vitamin B3

• **Vitamin B3 (Niacin)** = essential component of NAD and NADP coenzymes used in over 400 enzymatic reactions, especially energy metabolism in every cell. • **The Four Ds** — pellagra presents as dermatitis (sun-sensitive rash), diarrhea, dementia, and death if left untreated; historically devastated populations eating corn-only diets. • Corn contains niacin in a bound form (niacytin) unavailable to humans unless treated with lime water (nixtamalization). • 💡 Option A (Vitamin B2) is wrong because riboflavin deficiency causes ariboflavinosis — cracked lips and inflamed tongue, not pellagra; Option B (Vitamin B1) is wrong because thiamine deficiency causes beriberi — nerve and cardiac damage; Option D (Vitamin B12) is wrong because its deficiency causes megaloblastic (pernicious) anemia and nerve degeneration.

Correct Answer: C. Fats

• **Fats** = yield 9 kilocalories per gram upon complete oxidation — the highest energy density of any dietary macronutrient. • **Why so dense** — fat molecules are predominantly carbon and hydrogen with very little oxygen, so more electrons are available for transfer during cellular respiration. • The body stores excess energy as triglycerides in adipose tissue precisely because fat is such an efficient storage form. • 💡 Option A (Proteins) is wrong because they yield only 4 kcal/g and the body preferentially uses them for structural and regulatory roles, not fuel; Option B (Carbohydrates) is wrong because they also yield only 4 kcal/g, though they are the body's preferred quick fuel; Option D (Vitamins) is wrong because vitamins are micronutrients that act as coenzymes or antioxidants and release no caloric energy.

Correct Answer: A. Riboflavin

• **Riboflavin (Vitamin B2)** = water-soluble vitamin that forms the coenzymes FAD and FMN, which shuttle electrons during mitochondrial oxidative phosphorylation. • **Visible deficiency** — riboflavin shortage causes angular cheilitis (cracks at mouth corners), magenta tongue, and photophobia because it is needed in rapidly dividing mucosal cells. • Riboflavin is destroyed by light, which is why milk is sold in opaque containers. • 💡 Option B (Niacin) is wrong because niacin is vitamin B3, deficiency of which causes pellagra; Option C (Folic Acid) is wrong because folic acid is vitamin B9, critical for DNA synthesis and prevention of neural tube defects; Option D (Thiamine) is wrong because thiamine is vitamin B1, required for pyruvate decarboxylation in carbohydrate metabolism.

Correct Answer: B. Severe protein-calorie malnutrition

• **Marasmus** = a form of severe acute malnutrition caused by prolonged deficiency of both calories and protein, resulting in extreme wasting of muscle and subcutaneous fat. • **Clinical picture** — the child appears skeletal, with loose wrinkled skin, a large head relative to the wasted body, and is alert but irritable; differs from kwashiorkor which shows edema. • Marasmus is most common in the first year of life during early weaning from breast milk in food-insecure settings. • 💡 Option A (Vitamin D deficiency) is wrong because it causes rickets — soft, deformed bones — not whole-body wasting; Option C (Iron deficiency) is wrong because it leads to anemia — fatigue and pallor, not muscle wasting; Option D (Iodine deficiency) is wrong because it causes goiter and hypothyroidism, not caloric starvation.