2025 COMPREHENSIVE BCH 3025
EXAM 4 QUESTIONS WITH
ANSWERS NEW GENERATION
1. Which of the following is not required in the synthesis of fatty acids?
A) Acetyl-CoA
B) Biotin
C) HCO3- (CO2)
D) Malonyl-CoA
E) NADH - CORRECT ANSWER>>>NADH
2. Which of the following is not true of the reaction producing malonyl-CoA during fatty
acid synthesis?
A) It is stimulated by citrate.
B) It requires acyl carrier protein (ACP).
C) It requires CO2 (or bicarbonate).
D) One mole of ATP is converted to ADP + Pi for each malonyl-CoA synthesized.
E) The cofactor is biotin. - CORRECT ANSWER>>>It requires acyl carrier protein (ACP)
3. If malonyl-CoA is synthesized from 14CO2 and unlabeled acetyl-CoA, and the
labeled malonate is then used for fatty acid synthesis, the final product (fatty acid) will
have radioactive carbon in:
A) every C.
B) every even-numbered C-atom.
C) every odd-numbered C-atom.
D) no part of the molecule.
E) only the omega-carbon atom (farthest carbon from C-1). - CORRECT
ANSWER>>>no part of the molecule
4. Which one of the following statements best applies to synthesis of fatty acids in E.
coli extracts?
A) Acyl intermediates are thioesters of a low molecular weight protein called acyl carrier
protein.
B) CO2 or HCO3- is essential.
C) Reducing equivalents are provided by NADPH.
D) The ultimate source of all the carbon atoms in the fatty acid product is acetyl-CoA.
E) All of the above - CORRECT ANSWER>>>All of the above
5. In comparing fatty acid biosynthesis with beta-oxidation of fatty acids, which of the
following statements is incorrect?
,A) A thioester derivative of crotonic acid (trans-2-butenoic acid) is an intermediate in the
synthetic path, but not in the degradative path.
B) A thioester derivative of D-beta-hydroxybutyrate is an intermediate in the synthetic
path, not in the degradative path.
C) Fatty acid biosynthesis uses NADPH exclusively, whereas beta-oxidation uses NAD+
exclusively.
D) Fatty acid degradation is catalyzed by cytosolic enzymes; fatty acid synthesis by
mitochondrial enzymes.
E) The condensation of two moles of acetyl-CoA in the presence of a crude extract is
more rapid in bicarbonate buffer than in phosphate buffer at the same pH; the cleavage
of acetoacetyl-CoA proceeds equally well in either buffer. - CORRECT
ANSWER>>>Fatty acid biosynthesis uses NADPH exclusively, whereas beta-oxidation
uses NAD+ exclusively.
6. Which of the following is not true of the fatty acid synthase and the fatty acid beta-
oxidation systems?
A) A derivative of the vitamin pantothenic acid is involved.
B) Acyl-CoA derivatives are intermediates.
C) Double bonds are oxidized or reduced by pyridine nucleotide coenzymes.
D) The processes occur in different cellular compartments.
E) The processes occur in the mitochondrial matrix. - CORRECT ANSWER>>>The
processes occur in the mitochondrial matrix.
7. The rate-limiting step in fatty acid synthesis is: - CORRECT ANSWER>>>the reaction
catalyzed by acetyl-CoA carboxylase.
8. Which of the following is not true of the fatty acid elongation system of vertebrate
cells? - CORRECT ANSWER>>>The immediate precursor of the added carbons is
acetyl-CoA.
9. Which of the following is not true about precursors required for fatty acid synthesis in
animal cells? - CORRECT ANSWER>>>NADPH is produced in the nucleus by malic
enzyme
10. Which of these can be synthesized by plants but not by humans? - CORRECT
ANSWER>>>Linoleate [18:2(delta 9,12)]
11. The enzyme system for adding double bonds to saturated fatty acids requires all of
the following except: - CORRECT ANSWER>>>ATP
12. Which of these statements about eicosanoid synthesis is true? - CORRECT
ANSWER>>>An early step in the path to thromboxanes is blocked by ibuprofen.
, 13. The biosynthesis of triacylglycerols from acetate occurs mainly in: - CORRECT
ANSWER>>>humans after ingestion of excess carbohydrate.
14. The synthesis of both glycerophospholipids and triacylglycerols involves: -
CORRECT ANSWER>>>phosphatidic acid.
15. Which of these statements about triacylglycerol synthesis is correct? - CORRECT
ANSWER>>>Insulin stimulates conversion of dietary carbohydrate into triacylglycerols
16. A strategy that is not employed in the synthesis of phospholipids is: - CORRECT
ANSWER>>>condensation of CDP-diacylglycerol with alcohol.
17. All glycerol-containing phospholipids are synthesized from: - CORRECT
ANSWER>>>phosphatidic acid.
18. In E. coli the synthesis of phosphatidylethanolamine directly involves: - CORRECT
ANSWER>>>serine
19. In the synthesis of phosphatidylcholine from phosphatidylethanolamine, the methyl
group donor is: - CORRECT ANSWER>>>S-adenosylmethionine (adoMet)
20. Palmitoyl-CoA, , is a direct precursor of: - CORRECT ANSWER>>>sphingosine
21. CDP-diglyceride is not involved in the biosynthesis of: - CORRECT
ANSWER>>>sphingomyelin
22. Which of the following is true of sphingolipid synthesis? - CORRECT
ANSWER>>>CO2 is produced during the synthesis of ceramide from palmitate and
serine
23. Which of the following is not an intermediate in the synthesis of lanosterol from
acetyl-CoA? - CORRECT ANSWER>>>Malonyl-CoA
24. Cholesterol is synthesized from: - CORRECT ANSWER>>>acetyl-coA
25. A 30-carbon precursor of the steroid nucleus is - CORRECT ANSWER>>>squalene
26. Which of these statements about cholesterol synthesis is true? - CORRECT
ANSWER>>>Squalene synthesis from farnesyl pyrophosphate results in the release of
two moles of PPi for each mole of squalene formed.
27. Which of the following is derived from a sterol? - CORRECT ANSWER>>>Bile salts
28. Chylomicrons carry____in the______. - CORRECT ANSWER>>>triacylglycerols;
blood
EXAM 4 QUESTIONS WITH
ANSWERS NEW GENERATION
1. Which of the following is not required in the synthesis of fatty acids?
A) Acetyl-CoA
B) Biotin
C) HCO3- (CO2)
D) Malonyl-CoA
E) NADH - CORRECT ANSWER>>>NADH
2. Which of the following is not true of the reaction producing malonyl-CoA during fatty
acid synthesis?
A) It is stimulated by citrate.
B) It requires acyl carrier protein (ACP).
C) It requires CO2 (or bicarbonate).
D) One mole of ATP is converted to ADP + Pi for each malonyl-CoA synthesized.
E) The cofactor is biotin. - CORRECT ANSWER>>>It requires acyl carrier protein (ACP)
3. If malonyl-CoA is synthesized from 14CO2 and unlabeled acetyl-CoA, and the
labeled malonate is then used for fatty acid synthesis, the final product (fatty acid) will
have radioactive carbon in:
A) every C.
B) every even-numbered C-atom.
C) every odd-numbered C-atom.
D) no part of the molecule.
E) only the omega-carbon atom (farthest carbon from C-1). - CORRECT
ANSWER>>>no part of the molecule
4. Which one of the following statements best applies to synthesis of fatty acids in E.
coli extracts?
A) Acyl intermediates are thioesters of a low molecular weight protein called acyl carrier
protein.
B) CO2 or HCO3- is essential.
C) Reducing equivalents are provided by NADPH.
D) The ultimate source of all the carbon atoms in the fatty acid product is acetyl-CoA.
E) All of the above - CORRECT ANSWER>>>All of the above
5. In comparing fatty acid biosynthesis with beta-oxidation of fatty acids, which of the
following statements is incorrect?
,A) A thioester derivative of crotonic acid (trans-2-butenoic acid) is an intermediate in the
synthetic path, but not in the degradative path.
B) A thioester derivative of D-beta-hydroxybutyrate is an intermediate in the synthetic
path, not in the degradative path.
C) Fatty acid biosynthesis uses NADPH exclusively, whereas beta-oxidation uses NAD+
exclusively.
D) Fatty acid degradation is catalyzed by cytosolic enzymes; fatty acid synthesis by
mitochondrial enzymes.
E) The condensation of two moles of acetyl-CoA in the presence of a crude extract is
more rapid in bicarbonate buffer than in phosphate buffer at the same pH; the cleavage
of acetoacetyl-CoA proceeds equally well in either buffer. - CORRECT
ANSWER>>>Fatty acid biosynthesis uses NADPH exclusively, whereas beta-oxidation
uses NAD+ exclusively.
6. Which of the following is not true of the fatty acid synthase and the fatty acid beta-
oxidation systems?
A) A derivative of the vitamin pantothenic acid is involved.
B) Acyl-CoA derivatives are intermediates.
C) Double bonds are oxidized or reduced by pyridine nucleotide coenzymes.
D) The processes occur in different cellular compartments.
E) The processes occur in the mitochondrial matrix. - CORRECT ANSWER>>>The
processes occur in the mitochondrial matrix.
7. The rate-limiting step in fatty acid synthesis is: - CORRECT ANSWER>>>the reaction
catalyzed by acetyl-CoA carboxylase.
8. Which of the following is not true of the fatty acid elongation system of vertebrate
cells? - CORRECT ANSWER>>>The immediate precursor of the added carbons is
acetyl-CoA.
9. Which of the following is not true about precursors required for fatty acid synthesis in
animal cells? - CORRECT ANSWER>>>NADPH is produced in the nucleus by malic
enzyme
10. Which of these can be synthesized by plants but not by humans? - CORRECT
ANSWER>>>Linoleate [18:2(delta 9,12)]
11. The enzyme system for adding double bonds to saturated fatty acids requires all of
the following except: - CORRECT ANSWER>>>ATP
12. Which of these statements about eicosanoid synthesis is true? - CORRECT
ANSWER>>>An early step in the path to thromboxanes is blocked by ibuprofen.
, 13. The biosynthesis of triacylglycerols from acetate occurs mainly in: - CORRECT
ANSWER>>>humans after ingestion of excess carbohydrate.
14. The synthesis of both glycerophospholipids and triacylglycerols involves: -
CORRECT ANSWER>>>phosphatidic acid.
15. Which of these statements about triacylglycerol synthesis is correct? - CORRECT
ANSWER>>>Insulin stimulates conversion of dietary carbohydrate into triacylglycerols
16. A strategy that is not employed in the synthesis of phospholipids is: - CORRECT
ANSWER>>>condensation of CDP-diacylglycerol with alcohol.
17. All glycerol-containing phospholipids are synthesized from: - CORRECT
ANSWER>>>phosphatidic acid.
18. In E. coli the synthesis of phosphatidylethanolamine directly involves: - CORRECT
ANSWER>>>serine
19. In the synthesis of phosphatidylcholine from phosphatidylethanolamine, the methyl
group donor is: - CORRECT ANSWER>>>S-adenosylmethionine (adoMet)
20. Palmitoyl-CoA, , is a direct precursor of: - CORRECT ANSWER>>>sphingosine
21. CDP-diglyceride is not involved in the biosynthesis of: - CORRECT
ANSWER>>>sphingomyelin
22. Which of the following is true of sphingolipid synthesis? - CORRECT
ANSWER>>>CO2 is produced during the synthesis of ceramide from palmitate and
serine
23. Which of the following is not an intermediate in the synthesis of lanosterol from
acetyl-CoA? - CORRECT ANSWER>>>Malonyl-CoA
24. Cholesterol is synthesized from: - CORRECT ANSWER>>>acetyl-coA
25. A 30-carbon precursor of the steroid nucleus is - CORRECT ANSWER>>>squalene
26. Which of these statements about cholesterol synthesis is true? - CORRECT
ANSWER>>>Squalene synthesis from farnesyl pyrophosphate results in the release of
two moles of PPi for each mole of squalene formed.
27. Which of the following is derived from a sterol? - CORRECT ANSWER>>>Bile salts
28. Chylomicrons carry____in the______. - CORRECT ANSWER>>>triacylglycerols;
blood
