Biochemistry — MCQ Practice Questions & Answers

Question 1

Which of the following is NOT a component of a triglyceride molecule?

Accepted Answer

Correct answer: C. Phosphate group — Triglycerides consist of glycerol and three fatty acids connected by ester bonds. Phosphate groups are found in phospholipids, not triglycerides.

Answer

A. Glycerol

Answer

B. Fatty acids

Answer

D. Ester bonds

Question 2

What is the primary function of HDL cholesterol in the body?

Accepted Answer

Correct answer: B. Transport cholesterol from tissues to the liver for elimination — HDL (High-Density Lipoprotein) is known as 'good cholesterol' because it transports cholesterol from peripheral tissues back to the liver for degradation and excretion.

Answer

A. Provide energy to cells

Answer

C. Form cell membranes

Answer

D. Insulate nerve fibers

Question 3

Omega-3 fatty acids are beneficial for human health because they:

Accepted Answer

Correct answer: C. Reduce inflammation and support cardiovascular health — Omega-3 polyunsaturated fatty acids (found in fish, flaxseed) have anti-inflammatory properties and support heart health by reducing triglycerides and blood pressure.

Answer

A. Increase LDL cholesterol levels

Answer

B. Are saturated and stable at high temperatures

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D. Promote the synthesis of triglycerides

Question 4

Which lipid type is essential for maintaining the structural integrity of cell membranes?

Accepted Answer

Correct answer: A. Cholesterol and phospholipids — Cell membranes are composed of a phospholipid bilayer with embedded cholesterol molecules that regulate membrane fluidity and maintain structural integrity.

Answer

B. Triglycerides and waxes

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C. Steroids and eicosanoids

Answer

D. Only triglycerides

Question 5

What is the difference between saturated and unsaturated fatty acids in terms of their chemical structure?

Accepted Answer

Correct answer: B. Unsaturated acids contain one or more double bonds between carbon atoms — Saturated fatty acids have all single bonds between carbon atoms (straight chain), while unsaturated fatty acids have one or more C=C double bonds (kinked structure).

Answer

A. Saturated acids have more carbon atoms

Answer

C. Saturated acids are longer chain molecules

Answer

D. Unsaturated acids contain oxygen atoms

Question 6

Which of the following lipids is NOT a structural component of cell membranes?

Accepted Answer

Correct answer: D. Triacylglycerol — Triacylglycerols are storage lipids found primarily in adipose tissue. Phosphatidylcholine, cholesterol, and sphingomyelin are major components of cell membranes.

Answer

A. Phosphatidylcholine

Answer

B. Cholesterol

Answer

C. Sphingomyelin

Question 7

The rate-limiting enzyme in de novo fatty acid synthesis is:

Accepted Answer

Correct answer: A. Acetyl-CoA carboxylase — Acetyl-CoA carboxylase catalyzes the formation of malonyl-CoA from acetyl-CoA, which is the first committed and rate-limiting step in fatty acid synthesis.

Answer

B. Fatty acid synthase

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C. Carnitine palmitoyltransferase I

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D. Malonyl-CoA decarboxylase

Question 8

Beta-oxidation of fatty acids occurs primarily in which cellular compartment?

Accepted Answer

Correct answer: C. Mitochondrial matrix — Most fatty acids undergo beta-oxidation in the mitochondrial matrix. However, very long chain fatty acids (>20 carbons) are initially oxidized in peroxisomes.

Answer

A. Smooth endoplasmic reticulum

Answer

B. Rough endoplasmic reticulum

Answer

D. Peroxisomes (for very long chain fatty acids)

Biochemistry - MCQ Practice Questions