All Free Biochemistry MCQs with Answers

• A. B6 ad B12
• B. B12 and nicotinamie
• C. Folic acid and B6
• D. Folic acid and B12Vitamins & Supplements

Explanation: Serine hydroxymethyltransferase requires pyridoxal phosphate from vitamin B6, while tetrahydrofolate from folate accepts the hydroxymethyl…

• A. Chromium
• B. Iron
• C. Selenium
• D. Iodine

Explanation: Selenium has a vitamin E-sparing effect because selenium-dependent glutathione peroxidase reduces lipid peroxides, lowering the…

• A. Absorption requires bile pigments
• B. Synthesis is regulated at the reaction catalyzed by 15-hydroxylase
• C. Deficiency on adults leads to rickets
• D. Along with PTH, increases calcium resorption from bone

Explanation: Active vitamin D, together with PTH, increases calcium mobilization from bone when needed to maintain blood calcium.

• A. 2 unit of Vitamin A
• B. 1 unit of Vitamin A
• C. 3 unit of Vitamin A
• D. 4 unit of Vitamin A

Explanation: Beta-carotene is cleaved symmetrically in the intestine to form two molecules of retinal, which can be converted to vitamin A.

• A. Cold liver oil
• B. Fish liver oil
• C. Wheat germ oil
• D. Liver

Explanation: Wheat germ oil is exceptionally rich in tocopherols, the compounds collectively known as vitamin E.

• A. Is water soluble
• B. Is required for formation of clotting factors
• C. Maintains normal plasma calcium levels
• D. Deficiency causes impaired vision

Explanation: Vitamin A is required for rhodopsin formation in the retina, so its deficiency causes night blindness and impaired vision.

• A. Homocyteine methyl transferase
• B. Isocitrate dehydrogenase
• C. Glycogen synthase
• D. G-6-P dehydrogenase

Explanation: Vitamin B12 is a coenzyme for methionine synthase, also called homocysteine methyltransferase, which converts homocysteine to methionine.

• A. Stomach
• B. Terminal ileum
• C. Lower jejunum
• D. Proximal ileum

Explanation: Vitamin B12 binds intrinsic factor in the stomach and is absorbed as the complex in the terminal ileum.

• A. Biotin - carboxylated biotin
• B. Niacin - NAD+NADP
• C. Vitamin B - ATP
• D. Vitamin B2 - FMN+FAC

Explanation: Vitamin B vitamins form specific coenzymes such as TPP, FMN, FAD, NAD and NADP, not ATP itself.

• A. II
• B. VII
• C. IX
• D. X
• E. All of the above

Explanation: Vitamin K is required for gamma-carboxylation of clotting factors II, VII, IX and X, allowing them to bind calcium.

• A. Selenium
• B. Cobalt
• C. Iron
• D. Calcium

Explanation: Vitamin B12 is cobalamin, whose structure contains a central cobalt atom.

• A. Calcium
• B. Amino acids
• C. Fat
• D. Glucose

Explanation: Vitamin K is fat-soluble, so its intestinal absorption depends on normal fat absorption and bile-mediated micelle formation.

• A. Thiamin
• B. Riboflavin
• C. Pyridoxine
• D. Niacin

Explanation: The classic three Ds of pellagra are dermatitis, diarrhoea and dementia, caused by niacin deficiency.

• A. Retinol
• B. All of the above
• C. Retinoic acid
• D. Retinal

Explanation: Vitamin A activity is distributed among its main forms: retinol supports transport and storage, retinal participates in vision, and…

• A. Vitamin A
• B. Vitamin B
• C. Vitamin C
• D. Vitamin D

Explanation: Scurvy results from vitamin C deficiency, which impairs collagen synthesis and causes bleeding gums, poor wound healing and…

• A. Beri-beri
• B. Pernicious anemiaOrder Health Supplements
• C. Night blindness
• D. Pellagra

Explanation: Nicotinic acid is niacin, and its deficiency causes pellagra, classically remembered by the three Ds: dermatitis, diarrhoea and dementia.

• A. Ascorbic acid
• B. Nicotinic acid
• C. Pantothenic acid
• D. Folic acid

Explanation: Humans and guinea pigs cannot synthesize ascorbic acid because they lack L-gulonolactone oxidase, the final enzyme in its biosynthetic…

• A. Riboflavin
• B. Niacin
• C. Pyridoxine
• D. Pantothenic acid

Explanation: Niacin deficiency causes pellagra, which may include glossitis, dementia, gastrointestinal symptoms and rough, hyperkeratotic skin…

• A. Vitamin D deficiency
• B. Rickets
• C. Vitamin A deficiency
• D. Scurvy

Explanation: Rhodopsin is formed from opsin and retinal, the aldehyde derivative of vitamin A, in rod cells.

• A. Stimulation of hematopoiesis in red bone marrow
• B. Inhibition of antithrombin
• C. Prevention of capillary fragility
• D. Helps in formation of prothrombin

Explanation: Vitamin K is required for hepatic synthesis of prothrombin and several other clotting factors.