BCH 3033 General Biochemistry
Please answer all questions by bubbling in on the Answer Sheet, the BEST possible lettered answer.
1. The Citric Acid Cycle (CAC) enzyme that has a mechanism similar to pyruvate dehydrogenase ( and requires TPP, lipoic
acid, FAD) is:
a. malate dehydrogenase. b. succinate dehydrogenase. c. alpha-ketoglutyrate dehydrogenase. d. isocitrate
dehydrogenase. e. fumarase.
2. Consider the glycolytic enzyme enolase, the CAC enzyme that in principle works in reverse of enolase (when the CAC
cycle is moving forward) is:
a. citrate synthase. b. aconitase.c. isocitrate dehydrogenase. d. fumarase. e. hexokinase.
3. Suppose a mitochondrial preparation was given ONE pyruvate that was 14C-labeled in the carbonyl carbon.
The second round of the CAC would liberate % of the label as CO2.
a. 25%. b. 50%. c. 75%. d. 100%. e. 0% .
4. Suppose a mitochondrial preparation was given ONE pyruvate that was 14C-labeled of the carboxyl carbon.
The second round of the CAC cycle would liberate % of the label as CO2.
a. 25%. b. 50%. c. 75%. d. 100%. e. 0% .
5. When pyruvate is converted to glucose (gluconeogenesis), it is first converted to PEP by an enzyme system which must first:
+ +
a. oxidize ATP. b. fix CO2. c. reduce NAD . d. oxidize NAD . e. remove C=O.
6. In glycogen utilization, debranching enzyme is an alpha 1,6 hydrolase AND a:
a. phosphorylase. b. transglycosidase. c. dehydrogenase. d. glycosidase. e. oxidase.
7. The major immediate product of glycogen breakdown is:
a. glucose-6-phosphate. b. glucose-4-phosphate. c. glucose-2-phosphate.
d. glucose-1-phosphate. e. glucose.
8. Phosphorylase kinase phosphorylates glycogen synthase make it:
a. active. b. inactive. c. neutral. d. allosterically inhibited by ATP. e. dissolve in water.
9.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.
10. 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.
e. Not enough information is given to answer this question.
11. Malonate is a competitive inhibitor of succinate dehydrogenase. If malonate is added to a
mitochondrial preparation that is oxidizing pyruvate as a substrate, which of the following compounds
would you expect to decrease in concentration?
a. Citrate. b. Fumarate. c. Isocitrate. d. Pyruvate. e. Succinate.
12. Acetyl-CoA is not glucogenic in humans because humans lack:
Please answer all questions by bubbling in on the Answer Sheet, the BEST possible lettered answer.
1. The Citric Acid Cycle (CAC) enzyme that has a mechanism similar to pyruvate dehydrogenase ( and requires TPP, lipoic
acid, FAD) is:
a. malate dehydrogenase. b. succinate dehydrogenase. c. alpha-ketoglutyrate dehydrogenase. d. isocitrate
dehydrogenase. e. fumarase.
2. Consider the glycolytic enzyme enolase, the CAC enzyme that in principle works in reverse of enolase (when the CAC
cycle is moving forward) is:
a. citrate synthase. b. aconitase.c. isocitrate dehydrogenase. d. fumarase. e. hexokinase.
3. Suppose a mitochondrial preparation was given ONE pyruvate that was 14C-labeled in the carbonyl carbon.
The second round of the CAC would liberate % of the label as CO2.
a. 25%. b. 50%. c. 75%. d. 100%. e. 0% .
4. Suppose a mitochondrial preparation was given ONE pyruvate that was 14C-labeled of the carboxyl carbon.
The second round of the CAC cycle would liberate % of the label as CO2.
a. 25%. b. 50%. c. 75%. d. 100%. e. 0% .
5. When pyruvate is converted to glucose (gluconeogenesis), it is first converted to PEP by an enzyme system which must first:
+ +
a. oxidize ATP. b. fix CO2. c. reduce NAD . d. oxidize NAD . e. remove C=O.
6. In glycogen utilization, debranching enzyme is an alpha 1,6 hydrolase AND a:
a. phosphorylase. b. transglycosidase. c. dehydrogenase. d. glycosidase. e. oxidase.
7. The major immediate product of glycogen breakdown is:
a. glucose-6-phosphate. b. glucose-4-phosphate. c. glucose-2-phosphate.
d. glucose-1-phosphate. e. glucose.
8. Phosphorylase kinase phosphorylates glycogen synthase make it:
a. active. b. inactive. c. neutral. d. allosterically inhibited by ATP. e. dissolve in water.
9.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.
10. 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.
e. Not enough information is given to answer this question.
11. Malonate is a competitive inhibitor of succinate dehydrogenase. If malonate is added to a
mitochondrial preparation that is oxidizing pyruvate as a substrate, which of the following compounds
would you expect to decrease in concentration?
a. Citrate. b. Fumarate. c. Isocitrate. d. Pyruvate. e. Succinate.
12. Acetyl-CoA is not glucogenic in humans because humans lack:
