Biochemistry — MCQ Practice Questions & Answers

Question 1

In the context of lipid metabolism, what does beta-oxidation primarily accomplish?

Accepted Answer

Correct answer: B. Breaking down fatty acids into acetyl-CoA for energy production — Beta-oxidation is the catabolic pathway that breaks down fatty acids in the mitochondria, producing acetyl-CoA which enters the Krebs cycle for ATP production.

Answer

A. Synthesis of new fatty acids

Answer

C. Formation of cholesterol from acetyl-CoA

Answer

D. Conversion of glucose into triglycerides

Question 2

Which of the following is a consequence of excessive cholesterol accumulation in arteries?

Accepted Answer

Correct answer: B. Formation of atherosclerotic plaques causing narrowing of arteries — High cholesterol, particularly LDL cholesterol, can accumulate in artery walls forming atherosclerotic plaques, leading to arterial narrowing (atherosclerosis) and increased risk of heart disease.

Answer

A. Increased blood viscosity leading to faster flow

Answer

C. Enhanced oxygen delivery to tissues

Answer

D. Improved arterial elasticity

Question 3

A patient with familial hypercholesterolemia shows extremely high cholesterol levels. What is the most likely defect?

Accepted Answer

Correct answer: B. Absence or malfunction of LDL receptors — Familial hypercholesterolemia is caused by mutations in the LDL receptor gene, preventing cells from taking up LDL particles, resulting in elevated blood cholesterol levels.

Answer

A. Deficiency in HMG-CoA reductase

Answer

C. Excessive HDL production

Answer

D. Decreased acetyl-CoA levels

Question 4

Which enzyme catalyzes the rate-limiting step of cholesterol synthesis?

Accepted Answer

Correct answer: B. HMG-CoA reductase — HMG-CoA reductase catalyzes the conversion of HMG-CoA to mevalonate, the rate-limiting and key regulatory step in cholesterol biosynthesis. It is targeted by statin drugs.

Answer

A. Acetyl-CoA carboxylase

Answer

C. Fatty acid synthase

Answer

D. Lipoprotein lipase

Question 5

Phospholipids differ from triglycerides in that they contain:

Accepted Answer

Correct answer: B. A phosphate group and typically only two fatty acids — Phospholipids have a glycerol backbone with two fatty acids and a phosphate group, making them amphipathic. This structure is crucial for membrane formation.

Answer

A. Four fatty acid chains instead of three

Answer

C. No glycerol backbone

Answer

D. Cholesterol instead of glycerol

Question 6

A person consumes excessive saturated fats. Which lipoprotein level is most likely to increase?

Accepted Answer

Correct answer: B. VLDL (Very Low-Density Lipoprotein) — Excessive dietary saturated fat increases liver production of VLDL, which carries triglycerides and cholesterol. VLDL is converted to LDL in circulation, raising LDL levels.

Answer

A. HDL (High-Density Lipoprotein)

Answer

C. LDL derived from VLDL remains unchanged

Answer

D. Chylomicrons remain stable

Question 7

Which steroid hormone is synthesized from cholesterol in the adrenal cortex?

Accepted Answer

Correct answer: B. Cortisol — Cortisol and other corticosteroids are synthesized from cholesterol in the adrenal cortex through a series of enzymatic reactions involving cytochrome P450 enzymes.

Answer

A. Insulin

Answer

C. Thyroxine

Answer

D. Growth hormone

Question 8

The process of lipogenesis primarily occurs in which tissue during fed state?

Accepted Answer

Correct answer: C. Liver — The liver is the primary site of lipogenesis, where excess carbohydrates and amino acids are converted to fatty acids and triglycerides for storage and export via VLDL.

Answer

A. Skeletal muscle

Answer

B. Brain

Answer

D. Erythrocytes

Biochemistry - MCQ Practice Questions