All Free Biochemistry MCQs with Answers

• A. Glutathione peroxidase
• B. Myeloperoxidase
• C. Superoxide dismutase
• D. Catalase

Explanation: Superoxide dismutase, catalase and glutathione peroxidase detoxify reactive oxygen species.

• A. Altering the free energy of the action
• B. Inhibiting the backward reaction
• C. Decreasing the energy of activation
• D. Enhancing the forward reaction

Explanation: Enzymes accelerate reactions by lowering the activation energy required to reach the transition state.

• A. MN++
• B. Cu++
• C. Inorganic phosphate
• D. Mg++

Explanation: Most kinases transfer phosphate from ATP to a substrate and require Mg²⁺ to bind and properly orient ATP.

• A. Apo A-II
• B. Apo C-II
• C. Apo C-III
• D. Apo B-II

Explanation: Apolipoprotein C-II activates lipoprotein lipase, which hydrolyses triglycerides in chylomicrons and VLDL.

• A. HMG CoA reductase
• B. Pyrophospho mevalonate decarboxylase
• C. Lecithin cholesterol acyl transferase (LCAT)
• D. Phospho mevalonate kinase

Explanation: LCAT esterifies free cholesterol in plasma by transferring a fatty acid from lecithin to cholesterol, producing cholesteryl ester.

• A. Symmertrical bi leaflet structures
• B. Rigid assembly of protein, lipid and carbohydrate
• C. Lipid moiety is amphipathic
• D. Lipid and protein moiety are held by covalent interactions

Explanation: Membrane lipids are amphipathic, having a polar hydrophilic head and nonpolar hydrophobic tails that form the bilayer.

• A. Lipoproteins
• B. Aminoacids
• C. Bilirubin
• D. Cholesterol

Explanation: Bile acids are synthesized in the liver from cholesterol, which is converted into primary bile acids such as cholic acid and…

• A. Aldosterone
• B. Pregnenolone
• C. Estrogen
• D. Methyl testosterone

Explanation: Pregnenolone is formed from cholesterol and serves as an early steroid precursor that can lead to testosterone synthesis.

• A. Protein only
• B. Lipids only
• C. Lipids and proteins
• D. None of the above

Explanation: The cell membrane is a phospholipid bilayer containing embedded and associated proteins, which provide transport, receptors and enzymatic…

• A. Hydrogen bonding
• B. Not known
• C. Vander wall forces
• D. Hydrophobic interactions

Explanation: Membrane phospholipids spontaneously form bilayers because their nonpolar hydrocarbon tails avoid water while their polar heads interact…

• A. LDL (Low density lipoprotein)
• B. VLDL (Very low density lipoprotein)
• C. Chylomicron
• D. HDL (High density lipoprotein)

Explanation: LDL carries the greatest proportion of cholesterol, especially cholesteryl esters, among the listed lipoproteins.

• A. 40%
• B. 30%
• C. 50%
• D. 75%

Explanation: Dietary fat normally supplies about 30% of total energy intake in a balanced diet.

• A. Sphingomyelin
• B. Lecithin
• C. Cephalin
• D. Cerebroside

Explanation: Cerebrosides are glycolipids composed of ceramide plus a single sugar, not phosphate.

• A. Oleic acid
• B. Arachitlonic acid
• C. Linolenic acid
• D. Palmitic acid

Explanation: Oleic acid contains one carbon-carbon double bond, making it monounsaturated.

• A. Fructose
• B. Galactose
• C. Sucrose
• D. None of the above

Explanation: Cerebrosides are glycosphingolipids containing a single sugar, usually galactose in nervous tissue or glucose in some other tissues.

• A. Cholesterol
• B. FFA
• C. Lipoprotein
• D. Triglycerides

Explanation: Triglycerides accumulate in fatty liver when hepatic fatty-acid uptake and synthesis exceed oxidation and export in lipoproteins.

• A. Propionyl CoA
• B. Malonyl CoA
• C. Aceto acetyl CoA
• D. Fumaryl CoA

Explanation: Odd-chain fatty-acid oxidation ends with propionyl-CoA after repeated removal of two-carbon acetyl-CoA units.

• A. Creatine
• B. Carnitine
• C. Creatinine
• D. Coenzyme A

Explanation: Long-chain fatty acids cross the inner mitochondrial membrane through the carnitine shuttle.

• A. Glycerol
• B. Glucose
• C. Acetyl-CoA
• D. Acetone

Explanation: Ketone bodies are synthesized in the liver mitochondria from excess acetyl-CoA produced mainly by fatty-acid beta-oxidation.

• A. Carbohydrate
• B. Protein
• C. All of the above
• D. Fat

Explanation: Ketone bodies are produced mainly when fatty-acid oxidation supplies more acetyl-CoA than the citric acid cycle can use, such as during…