Chapter 16 Biochemistry Test Bank
Written By Lehninger.
1. Which of the following is not true of the reaction catalyzed by the pyruvate dehydrogenase
complex?
A) Biotin participates in the decarboxylation.
B) Both NAD+ and a flavin nucleotide act as electron carriers.
C) The reaction occurs in the mitochondrial matrix.
D) The substrate is held by the lipoyl-lysine "swinging arm."
E) Two different cofactors containing —SH groups participate. - Answer A
2. Which of the below is not required for the oxidative decarboxylation of pyruvate to form
acetyl-CoA?
A) ATP
B) CoA-SH
C) FAD
D) Lipoic acid
E) NAD+ - Answer A
3. Which combination of cofactors is involved in the conversion of pyruvate to acetyl-CoA?
A) Biotin, FAD, and TPP
B) Biotin, NAD+, and FAD
C) NAD+, biotin, and TPP
D) Pyridoxal phosphate, FAD, and lipoic acid
E) TPP, lipoic acid, and NAD+ - Answer E
4. Which of the following statements about the oxidative decarboxylation of pyruvate in aerobic
conditions in animal cells is correct?
, D) The pyruvate dehydrogenase complex uses all of the following as cofactors: NAD+, lipoic acid,
pyridoxal phosphate (PLP), and FAD.
E) The reaction is so important to energy production that pyruvate dehydrogenase operates at
full speed under all conditions. - Answer A
5. Glucose labeled with 14C in C-3 and C-4 is completely converted to acetyl-CoA via glycolysis
and the pyruvate dehydrogenase complex. What percentage of the acetyl-CoA molecules
formed will be labeled with 14C, and in which position of the acetyl moiety will the 14C label be
found?
A) 100% of the acetyl-CoA will be labeled at C-1 (carboxyl).
B) 100% of the acetyl-CoA will be labeled at C-2.
C) 50% of the acetyl-CoA will be labeled, all at C-2 (methyl).
D) No label will be found in the acetyl-CoA molecules.
E) Not enough information is given to answer this question. - Answer D
6. Which of the following is not true of the citric acid cycle?
A) All enzymes of the cycle are located in the cytoplasm, except succinate dehydrogenase,
which is bound to the inner mitochondrial membrane.
B) In the presence of malonate, one would expect succinate to accumulate.
C) Oxaloacetate is used as a substrate but is not consumed in the cycle.
D) Succinate dehydrogenase channels electrons directly into the electron transfer chain.
E) The condensing enzyme is subject to allosteric regulation by ATP and NADH. - Answer A
7. Acetyl-CoA labeled with 14C in both of its acetate carbon atoms is incubated with unlabeled
oxaloacetate and a crude tissue preparation capable of carrying out the reactions of the citric
acid cycle. After one turn of the cycle, oxaloacetate would have 14C in:
A) all four carbon atoms.
B) no pattern that is predictable from the information provided.
C) none of its carbon atoms.
D) the keto carbon and one of the carboxyl carbons.
E) the two carboxyl carbons. - Answer A
Written By Lehninger.
1. Which of the following is not true of the reaction catalyzed by the pyruvate dehydrogenase
complex?
A) Biotin participates in the decarboxylation.
B) Both NAD+ and a flavin nucleotide act as electron carriers.
C) The reaction occurs in the mitochondrial matrix.
D) The substrate is held by the lipoyl-lysine "swinging arm."
E) Two different cofactors containing —SH groups participate. - Answer A
2. Which of the below is not required for the oxidative decarboxylation of pyruvate to form
acetyl-CoA?
A) ATP
B) CoA-SH
C) FAD
D) Lipoic acid
E) NAD+ - Answer A
3. Which combination of cofactors is involved in the conversion of pyruvate to acetyl-CoA?
A) Biotin, FAD, and TPP
B) Biotin, NAD+, and FAD
C) NAD+, biotin, and TPP
D) Pyridoxal phosphate, FAD, and lipoic acid
E) TPP, lipoic acid, and NAD+ - Answer E
4. Which of the following statements about the oxidative decarboxylation of pyruvate in aerobic
conditions in animal cells is correct?
, D) The pyruvate dehydrogenase complex uses all of the following as cofactors: NAD+, lipoic acid,
pyridoxal phosphate (PLP), and FAD.
E) The reaction is so important to energy production that pyruvate dehydrogenase operates at
full speed under all conditions. - Answer A
5. Glucose labeled with 14C in C-3 and C-4 is completely converted to acetyl-CoA via glycolysis
and the pyruvate dehydrogenase complex. What percentage of the acetyl-CoA molecules
formed will be labeled with 14C, and in which position of the acetyl moiety will the 14C label be
found?
A) 100% of the acetyl-CoA will be labeled at C-1 (carboxyl).
B) 100% of the acetyl-CoA will be labeled at C-2.
C) 50% of the acetyl-CoA will be labeled, all at C-2 (methyl).
D) No label will be found in the acetyl-CoA molecules.
E) Not enough information is given to answer this question. - Answer D
6. Which of the following is not true of the citric acid cycle?
A) All enzymes of the cycle are located in the cytoplasm, except succinate dehydrogenase,
which is bound to the inner mitochondrial membrane.
B) In the presence of malonate, one would expect succinate to accumulate.
C) Oxaloacetate is used as a substrate but is not consumed in the cycle.
D) Succinate dehydrogenase channels electrons directly into the electron transfer chain.
E) The condensing enzyme is subject to allosteric regulation by ATP and NADH. - Answer A
7. Acetyl-CoA labeled with 14C in both of its acetate carbon atoms is incubated with unlabeled
oxaloacetate and a crude tissue preparation capable of carrying out the reactions of the citric
acid cycle. After one turn of the cycle, oxaloacetate would have 14C in:
A) all four carbon atoms.
B) no pattern that is predictable from the information provided.
C) none of its carbon atoms.
D) the keto carbon and one of the carboxyl carbons.
E) the two carboxyl carbons. - Answer A
