Biochemistry: Lipid Metabolism & Cholesterol Regulation Practice
Pack 2026 |WGU
1. Where does the synthesis of fatty acids primarily occur within a cell?
A. Mitochondrial matrix
B. Nucleus
C. Lysosome
D. Cytosol
Answer: D
Rationale: Fatty acid synthesis occurs in the cytosol, whereas fatty acid oxidation (beta-
oxidation) takes place in the mitochondrial matrix.
2. What is the rate-limiting enzyme in fatty acid synthesis?
A. Fatty acid synthase
B. HMG-CoA Reductase
C. Carnitine Palmitoyltransferase I
D. Acetyl-CoA Carboxylase (ACC)
Answer: D
Rationale: Acetyl-CoA Carboxylase (ACC) catalyzes the conversion of acetyl-CoA to
malonyl-CoA, which is the regulated step of lipogenesis.
,3. Which molecule is the primary carrier of acetyl groups from the mitochondria
to the cytosol for fatty acid synthesis?
A. Citrate
B. Pyruvate
C. Malate
D. Oxaloacetate
Answer: A
Rationale: Acetyl-CoA cannot cross the mitochondrial membrane directly; it combines
with oxaloacetate to form citrate, which is then transported to the cytosol.
4. What cofactor is required by Acetyl-CoA Carboxylase (ACC) for its activity?
A. Thiamine
B. Biotin
C. Niacin
D. Riboflavin
Answer: B
Rationale: ACC is a biotin-dependent enzyme that uses bicarbonate and ATP to
carboxylate acetyl-CoA.
5. Which molecule acts as a potent inhibitor of Carnitine Palmitoyltransferase I
(CPT-1), preventing the entry of fatty acids into the mitochondria?
A. Acetyl-CoA
B. Citrate
C. Malonyl-CoA
D. Palmitate
Answer: C
Rationale: Malonyl-CoA, produced during fatty acid synthesis, inhibits CPT-1 to prevent a
futile cycle where newly synthesized fatty acids are immediately oxidized.
, 6. What is the primary reducing agent required for fatty acid synthesis?
A. NADPH
B. FADH2
C. NADH
D. ATP
Answer: A
Rationale: NADPH provides the reducing power for the biosynthetic reactions of fatty acid
synthesis, primarily sourced from the Pentose Phosphate Pathway.
7. How many carbons are in a molecule of Palmitate, the primary product of the
Fatty Acid Synthase complex?
A. 12
B. 16
C. 14
D. 18
Answer: B
Rationale: Palmitate (palmitic acid) is a 16-carbon saturated fatty acid and is the standard
end product of the fatty acid synthase system.
8. Which enzyme is responsible for the activation of fatty acids by attaching
Coenzyme A before they enter the oxidation pathway?
A. Thiolase
B. Acyl-CoA Synthetase
C. Carnitine Acyltransferase
D. Enoyl-CoA Hydratase
Answer: B
Rationale: Acyl-CoA Synthetase activates fatty acids in the cytosol by converting them into
fatty acyl-CoA, requiring ATP.
Pack 2026 |WGU
1. Where does the synthesis of fatty acids primarily occur within a cell?
A. Mitochondrial matrix
B. Nucleus
C. Lysosome
D. Cytosol
Answer: D
Rationale: Fatty acid synthesis occurs in the cytosol, whereas fatty acid oxidation (beta-
oxidation) takes place in the mitochondrial matrix.
2. What is the rate-limiting enzyme in fatty acid synthesis?
A. Fatty acid synthase
B. HMG-CoA Reductase
C. Carnitine Palmitoyltransferase I
D. Acetyl-CoA Carboxylase (ACC)
Answer: D
Rationale: Acetyl-CoA Carboxylase (ACC) catalyzes the conversion of acetyl-CoA to
malonyl-CoA, which is the regulated step of lipogenesis.
,3. Which molecule is the primary carrier of acetyl groups from the mitochondria
to the cytosol for fatty acid synthesis?
A. Citrate
B. Pyruvate
C. Malate
D. Oxaloacetate
Answer: A
Rationale: Acetyl-CoA cannot cross the mitochondrial membrane directly; it combines
with oxaloacetate to form citrate, which is then transported to the cytosol.
4. What cofactor is required by Acetyl-CoA Carboxylase (ACC) for its activity?
A. Thiamine
B. Biotin
C. Niacin
D. Riboflavin
Answer: B
Rationale: ACC is a biotin-dependent enzyme that uses bicarbonate and ATP to
carboxylate acetyl-CoA.
5. Which molecule acts as a potent inhibitor of Carnitine Palmitoyltransferase I
(CPT-1), preventing the entry of fatty acids into the mitochondria?
A. Acetyl-CoA
B. Citrate
C. Malonyl-CoA
D. Palmitate
Answer: C
Rationale: Malonyl-CoA, produced during fatty acid synthesis, inhibits CPT-1 to prevent a
futile cycle where newly synthesized fatty acids are immediately oxidized.
, 6. What is the primary reducing agent required for fatty acid synthesis?
A. NADPH
B. FADH2
C. NADH
D. ATP
Answer: A
Rationale: NADPH provides the reducing power for the biosynthetic reactions of fatty acid
synthesis, primarily sourced from the Pentose Phosphate Pathway.
7. How many carbons are in a molecule of Palmitate, the primary product of the
Fatty Acid Synthase complex?
A. 12
B. 16
C. 14
D. 18
Answer: B
Rationale: Palmitate (palmitic acid) is a 16-carbon saturated fatty acid and is the standard
end product of the fatty acid synthase system.
8. Which enzyme is responsible for the activation of fatty acids by attaching
Coenzyme A before they enter the oxidation pathway?
A. Thiolase
B. Acyl-CoA Synthetase
C. Carnitine Acyltransferase
D. Enoyl-CoA Hydratase
Answer: B
Rationale: Acyl-CoA Synthetase activates fatty acids in the cytosol by converting them into
fatty acyl-CoA, requiring ATP.
