BCH3025 Exam 4 UPDATED ACTUAL
Exam Questions and CORRECT Answers
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 - E) NADH
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 - B) It requires acyl carrier protein
(ACP).
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 - D)
no part of the molecule.
,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 - E) All of the above
In comparing fatty acid biosynthesis with β 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-β-hydroxybutyrate is an intermediate in the synthetic path, not in
the degradative path.
C) Fatty acid biosynthesis uses NADPH exclusively, whereas β 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 - D) Fatty acid degradation
is catalyzed by cytosolic enzymes; fatty acid synthesis by mitochondrial enzymes.
Which of the following is not true of the fatty acid synthase and the fatty acid β-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 - E) The
processes occur in the mitochondrial matrix.
The rate-limiting step in fatty acid synthesis is:
A) condensation of acetyl-CoA and malonyl-CoA.
B) formation of acetyl-CoA from acetate.
C) formation of malonyl-CoA from malonate and coenzyme A.
D) the reaction catalyzed by acetyl-CoA carboxylase.
E) the reduction of the acetoacetyl group to a β-hydroxybutyryl group. - CORRECT
ANSWER - D) the reaction catalyzed by acetyl-CoA carboxylase.
Which of the following is not true of the fatty acid elongation system of vertebrate cells?
A) It involves the same four-step sequence seen in the fatty acid synthase complex.
B) It is located in the smooth endoplasmic reticulum.
C) It produces stearoyl-CoA by the extension of palmitoyl-CoA.
D) It uses malonyl-CoA as a substrate.
E) The immediate precursor of the added carbons is acetyl-CoA. - CORRECT ANSWER -
E) The immediate precursor of the added carbons is acetyl-CoA.
Which of the following is not true about precursors required for fatty acid synthesis in animal
cells?
A) NADPH is produced in the cytosol by the pentose phosphate pathway.
B) NADPH is produced in the nucleus by malic enzyme.
C) Acetyl-CoA is transported out of the mitochondrion via the citrate shuttle.
, D) CoA is not transported across the mitochondrial membrane.
E) Malonyl-CoA is formed in the cytosol. - CORRECT ANSWER - B) NADPH is
produced in the nucleus by malic enzyme.
Which of these can be synthesized by plants but not by humans?
A) Linoleate [18:2(Δ9,12)]
B) Palmitate (16:0)
C) Phosphatidylcholine
D) Pyruvate
E) Stearate (18:0) - CORRECT ANSWER - A) Linoleate [18:2(Δ9,12)]
The enzyme system for adding double bonds to saturated fatty acids requires all of the following
except:
A) a mixed-function oxidase.
B) ATP.
C) cytochrome b5.
D) molecular oxygen (O2).
E) NADPH. - CORRECT ANSWER - B) ATP.
Which of these statements about eicosanoid synthesis is true?
A) An early step in the path to thromboxanes is blocked by ibuprofen.
B) Arachidonate is derived mainly by hydrolysis of triacylglycerols.
C) Aspirin acts by blocking the synthesis of arachidonate.
D) Plants can synthesize leukotrienes, but humans cannot.
E) Thromboxanes are produced from arachidonate via the "linear" path. - CORRECT
ANSWER - A) An early step in the path to thromboxanes is blocked by ibuprofen.
Exam Questions and CORRECT Answers
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 - E) NADH
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 - B) It requires acyl carrier protein
(ACP).
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 - D)
no part of the molecule.
,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 - E) All of the above
In comparing fatty acid biosynthesis with β 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-β-hydroxybutyrate is an intermediate in the synthetic path, not in
the degradative path.
C) Fatty acid biosynthesis uses NADPH exclusively, whereas β 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 - D) Fatty acid degradation
is catalyzed by cytosolic enzymes; fatty acid synthesis by mitochondrial enzymes.
Which of the following is not true of the fatty acid synthase and the fatty acid β-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 - E) The
processes occur in the mitochondrial matrix.
The rate-limiting step in fatty acid synthesis is:
A) condensation of acetyl-CoA and malonyl-CoA.
B) formation of acetyl-CoA from acetate.
C) formation of malonyl-CoA from malonate and coenzyme A.
D) the reaction catalyzed by acetyl-CoA carboxylase.
E) the reduction of the acetoacetyl group to a β-hydroxybutyryl group. - CORRECT
ANSWER - D) the reaction catalyzed by acetyl-CoA carboxylase.
Which of the following is not true of the fatty acid elongation system of vertebrate cells?
A) It involves the same four-step sequence seen in the fatty acid synthase complex.
B) It is located in the smooth endoplasmic reticulum.
C) It produces stearoyl-CoA by the extension of palmitoyl-CoA.
D) It uses malonyl-CoA as a substrate.
E) The immediate precursor of the added carbons is acetyl-CoA. - CORRECT ANSWER -
E) The immediate precursor of the added carbons is acetyl-CoA.
Which of the following is not true about precursors required for fatty acid synthesis in animal
cells?
A) NADPH is produced in the cytosol by the pentose phosphate pathway.
B) NADPH is produced in the nucleus by malic enzyme.
C) Acetyl-CoA is transported out of the mitochondrion via the citrate shuttle.
, D) CoA is not transported across the mitochondrial membrane.
E) Malonyl-CoA is formed in the cytosol. - CORRECT ANSWER - B) NADPH is
produced in the nucleus by malic enzyme.
Which of these can be synthesized by plants but not by humans?
A) Linoleate [18:2(Δ9,12)]
B) Palmitate (16:0)
C) Phosphatidylcholine
D) Pyruvate
E) Stearate (18:0) - CORRECT ANSWER - A) Linoleate [18:2(Δ9,12)]
The enzyme system for adding double bonds to saturated fatty acids requires all of the following
except:
A) a mixed-function oxidase.
B) ATP.
C) cytochrome b5.
D) molecular oxygen (O2).
E) NADPH. - CORRECT ANSWER - B) ATP.
Which of these statements about eicosanoid synthesis is true?
A) An early step in the path to thromboxanes is blocked by ibuprofen.
B) Arachidonate is derived mainly by hydrolysis of triacylglycerols.
C) Aspirin acts by blocking the synthesis of arachidonate.
D) Plants can synthesize leukotrienes, but humans cannot.
E) Thromboxanes are produced from arachidonate via the "linear" path. - CORRECT
ANSWER - A) An early step in the path to thromboxanes is blocked by ibuprofen.
