All Free Biochemistry MCQs with Answers

• A. Thiamine
• B. Niacin
• C. Biotin
• D. Phylloquinone

Explanation: Avidin, a protein in raw egg white, binds biotin tightly and prevents its absorption.

• A. Amine group transfer
• B. Transamination reaction
• C. Methyl group transfer
• D. Redox reactions

Explanation: Niacin forms NAD/NADP and riboflavin forms FAD/FMN, all of which carry electrons in oxidation-reduction reactions.

• A. Vit C
• B. Vit A
• C. Vit B2
• D. Vit D

Explanation: Vitamin C is required for hydroxylation of proline and lysine during collagen maturation.

• A. Thiamine
• B. Riboflavin
• C. Niacin
• D. Folic acid

Explanation: Riboflavin deficiency commonly causes angular cheilosis, cracks at the corners of the mouth, along with glossitis and other mucocutaneous…

• A. Tyrosine
• B. Histidine
• C. Threonine
• D. Tryptophan

Explanation: Tryptophan can be converted into niacin through the kynurenine pathway, although the conversion is inefficient and requires vitamin B6.

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

Explanation: Coenzyme A contains pantothenic acid as its vitamin component, contributing the phosphopantetheine group that carries acyl groups.

• A. Milk
• B. Cabbage
• C. Guava
• D. Radish

Explanation: Milk contains only a small amount of vitamin C, whereas guava, cabbage and radish provide comparatively better sources.

• A. Vit B1 deficiency
• B. Vit B12 deficiency
• C. Vit C deficiency
• D. Vit D deficiency

Explanation: Pernicious anaemia results from impaired absorption of vitamin B12, usually because intrinsic factor is absent or defective.

• A. Niacin
• B. Thiamine
• C. Ascorbic acid
• D. Folic acid

Explanation: Folic acid, in its tetrahydrofolate forms, carries and transfers one-carbon units needed for nucleotide and amino-acid synthesis.

• A. 50 - 60 mg
• B. 30 - 40 mg
• C. 60 - 100 mg
• D. 100 - 150 mg

Explanation: The traditionally quoted average daily requirement for vitamin C is about 60 mg, placing it in the 50–60 mg range.

• A. Vitamin D deficiency
• B. Vitamin A deficiency
• C. Vitamin C deficiency
• D. Vitamin K deficiency

Explanation: Vitamin A maintains the health of the conjunctiva and cornea, so its deficiency can cause xerophthalmia and eventually blindness.

• A. Vitamin B12 deficiency
• B. Ascorbic acid deficiency
• C. Infection
• D. B & C option

Explanation: Vitamin C deficiency impairs collagen formation, while infection increases tissue damage and delays repair; both can slow wound healing.

• A. Is a reducing agent
• B. Decrease iron absorption
• C. Is harmless in high doses
• D. Is requirement for lysyl oxidase

Explanation: Ascorbic acid is a strong reducing agent and helps maintain iron in its absorbable ferrous form.

• A. Vitamin A
• B. Vitamin E
• C. Vitamin K
• D. Vitamin D

Explanation: Tocopherol is the chemical name for vitamin E, a fat-soluble antioxidant that protects membrane lipids from oxidation.

• A. Post transcription
• B. Golgi complex
• C. Post translation
• D. Endoplasmic reticulum

Explanation: Vitamin K is required for post-translational gamma-carboxylation of specific glutamate residues in clotting factors, enabling them to bind…

• A. Its active form is calcitriol
• B. Increase calcium absorption from the intestines
• C. Its deficiency results in rickets
• D. Its decrease cause phosphate reabsorption from the kidneys

Explanation: Calcitriol is the active form of vitamin D and increases intestinal calcium absorption; its deficiency causes rickets.

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

Explanation: Pyridoxine is converted to pyridoxal phosphate, which acts as a coenzyme in amino-acid decarboxylation, transamination and…

• A. Eye
• B. Kidneys
• C. Adrenal cortex
• D. Testes

Explanation: The adrenal cortex has a particularly high concentration of vitamin C, where it supports steroid-hormone synthesis and adrenal function.

• A. Folic acid
• B. Niacinamide
• C. Cyano cobolamine
• D. Pyridoxine

Explanation: A tryptophan load normally produces niacin through a pathway requiring pyridoxal phosphate.

• A. Folic acid
• B. Vit E
• C. Thiamine
• D. Cobalamine

Explanation: Folate, as tetrahydrofolate derivatives, carries the one-carbon units transferred during glycine cleavage and related glycine reactions.