Question 1

Which of the following enzymatic reactions is favorable both under physiological conditions and under standard conditions?

Accepted Answer

A) The reaction catalyzed by isocitrate dehydrogenase. 
B) The reaction catalyzed by malate dehydrogenase. 
C) The reaction catalyzed by succinate dehydrogenase. 
D) all of the above 
E) none of the above 
A) The reaction catalyzed by isocitrate dehydrogenase. 
B) The reaction catalyzed by malate dehydrogenase. 
C) The reaction catalyzed by succinate dehydrogenase. 
D) all of the above 
E) none of the above

Question 2

Which of the following enzymes of the citric acid cycle is inhibited by ATP?

Accepted Answer

A) "citrate synthase" 
B) "isocitrate dehydrogenase" 
C) "$\alpha$-ketoglutarate dehydrogenase" 
D) "succinyl-CoA synthetase" 
E) "A and B" 
A) "citrate synthase" 
B) "isocitrate dehydrogenase" 
C) "$\alpha$-ketoglutarate dehydrogenase" 
D) "succinyl-CoA synthetase" 
E) "A and B"

Question 3

Matching
Choose the correct answer from the list.Not all the answers will be used.

-The enzyme ______ is part of the glyoxylate cycle that occurs in plants,bacteria,and fungi.

Accepted Answer

A)  oxaloacetate 
B)  malate synthase 
C)  malate 
D)  malonate 
E)  Krebs
F) aconitase
G) succinyl-CoA synthetase
H) α-ketoglutarate
I) carbon dioxide
J) malate dehydrogenase
K) isocitrate
L) succinate dehydrogenase 
A)  oxaloacetate 
B)  malate synthase 
C)  malate 
D)  malonate 
E)  Krebs
F) aconitase
G) succinyl-CoA synthetase
H) α-ketoglutarate
I) carbon dioxide
J) malate dehydrogenase
K) isocitrate
L) succinate dehydrogenase

Question 4

Matching
Choose the correct answer from the list.Not all the answers will be used.

-_____ and pyruvate can be combined in an ATP dependent reaction that regenerates one of the key intermediates in the citric acid cycle.

Accepted Answer

A)  oxaloacetate 
B)  malate synthase 
C)  malate 
D)  malonate 
E)  Krebs
F) aconitase
G) succinyl-CoA synthetase
H) α-ketoglutarate
I) carbon dioxide
J) malate dehydrogenase
K) isocitrate
L) succinate dehydrogenase 
A)  oxaloacetate 
B)  malate synthase 
C)  malate 
D)  malonate 
E)  Krebs
F) aconitase
G) succinyl-CoA synthetase
H) α-ketoglutarate
I) carbon dioxide
J) malate dehydrogenase
K) isocitrate
L) succinate dehydrogenase

Question 5

Which of the following would decrease activity of the citric acid cycle overall?
(I)high concentration of NADH
(II)high concentration of Ca2+
(III)high concentration of ATP
(IV)high concentration of citrate

Accepted Answer

A) I only 
B) I,II,III,IV 
C) I,III 
D) I,III,IV 
E) I,IV 
A) I only 
B) I,II,III,IV 
C) I,III 
D) I,III,IV 
E) I,IV

Question 6

Bioinformatics has identified some enzymes used in the citric acid cycle in primitive bacteria.Once such a cycle utilized many of the citric acid cycle intermediates but occurred in the reverse direction.Researchers suspect which of the following based on this information?

Accepted Answer

A) Researchers suspect that the "original" citric acid cycle was used by all species. 
B) Researchers suspect that portions of the reverse cycle may have been responsible for fixing CO2 
C) Researchers suspect that early methods for converting pyruvate to acetyl CoA did not exist. 
D) Researchers suspect that the current "clockwise" version of the citric acid cycle could be used to help humans feed off CO2. 
E) Researchers suspect that primitive prokaryotic use of the citric acid enzymes were focused on the production of CO2 rather than the use of CO2. 
A) Researchers suspect that the "original" citric acid cycle was used by all species. 
B) Researchers suspect that portions of the reverse cycle may have been responsible for fixing CO2 
C) Researchers suspect that early methods for converting pyruvate to acetyl CoA did not exist. 
D) Researchers suspect that the current "clockwise" version of the citric acid cycle could be used to help humans feed off CO2. 
E) Researchers suspect that primitive prokaryotic use of the citric acid enzymes were focused on the production of CO2 rather than the use of CO2.

Question 7

Which of the following steps of the citric acid cycle conserves the energy of a high energy thioester bond?

Accepted Answer

A) the reaction catalyzed by succinate dehydrogenase. 
B) the reaction that produces oxalacetate. 
C) the condensation reaction that produces citrate. 
D) the reaction catalyzed by α-ketoglutarate dehydrogenase. 
E) the conversion of citrate to isocitrate. 
A) the reaction catalyzed by succinate dehydrogenase. 
B) the reaction that produces oxalacetate. 
C) the condensation reaction that produces citrate. 
D) the reaction catalyzed by α-ketoglutarate dehydrogenase. 
E) the conversion of citrate to isocitrate.

Question 8

If acetyl-CoA labeled with 14C,as shown in the figure to the right,were used as the substrate for the citric acid cycle,which of the following intermediates would be produced during the first round of the cycle?

Accepted Answer

A) 
  
B) 
  
C) 
  
D) 
  
E) 
  
A) 
  
B) 
  
C) 
  
D) 
  
E)

Question 9

The reaction catalyzed by _____ requires an enzyme bound flavin coenzyme.

Accepted Answer

A) "isocitrate dehydrogenase" 
B) "$\alpha$-ketoglutarate dehydrogenase" 
C) "succinyl-CoA synthetase" 
D) "succinate dehydrogenase" 
E) "malate dehydrogenase" 
A) "isocitrate dehydrogenase" 
B) "$\alpha$-ketoglutarate dehydrogenase" 
C) "succinyl-CoA synthetase" 
D) "succinate dehydrogenase" 
E) "malate dehydrogenase"

Question 10

Matching
Choose the correct answer from the list.Not all the answers will be used.

-______ is used in the first reaction of the citric acid cycle and regenerated upon completion of one turn of the citric acid cycle.

Accepted Answer

A)  oxaloacetate 
B)  malate synthase 
C)  malate 
D)  malonate 
E)  Krebs
F) aconitase
G) succinyl-CoA synthetase
H) α-ketoglutarate
I) carbon dioxide
J) malate dehydrogenase
K) isocitrate
L) succinate dehydrogenase 
A)  oxaloacetate 
B)  malate synthase 
C)  malate 
D)  malonate 
E)  Krebs
F) aconitase
G) succinyl-CoA synthetase
H) α-ketoglutarate
I) carbon dioxide
J) malate dehydrogenase
K) isocitrate
L) succinate dehydrogenase

Question 11

Which of the following represents a point of regulation for the citric acid cycle?
(I)pyruvate dehydrogenase complex
(II)aconitase
(III)isocitrate dehydrogenase
(IV)fumarase

Accepted Answer

A) I,II,III,IV 
B) I,II,IV 
C) II,III 
D) I,III 
E) I,IV 
A) I,II,III,IV 
B) I,II,IV 
C) II,III 
D) I,III 
E) I,IV

Question 12

One turn of the citric acid cycle generates

Accepted Answer

A) 2 FADH2,3 ATP,1 NADH 
B) 1 NAD+,2FADH2,1 ATP 
C) 1 GTP,3 NADH,1 FADH2 
D) 1 FAD,2 ATP,3 NADH 
E) 1 FADH2,1GTP,2 NADH 
A) 2 FADH2,3 ATP,1 NADH 
B) 1 NAD+,2FADH2,1 ATP 
C) 1 GTP,3 NADH,1 FADH2 
D) 1 FAD,2 ATP,3 NADH 
E) 1 FADH2,1GTP,2 NADH

Question 13

Which of the following utilizes intermediates of the citric acid cycle?
(I)gluconeogenesis
(II)amino acid biosynthesis
(III)fatty acid oxidation
(IV)glycolysis

Accepted Answer

A) I only 
B) II only 
C) I,II,III 
D) I,II 
E) I,IV 
A) I only 
B) II only 
C) I,II,III 
D) I,II 
E) I,IV

Question 14

Which of the following organisms does not utilize the glyxolate cycle?

Accepted Answer

A) trees 
B) bacteria 
C) fungi 
D) mammals 
E) All of the above utilize the glyxolate cycle when necessary. 
A) trees 
B) bacteria 
C) fungi 
D) mammals 
E) All of the above utilize the glyxolate cycle when necessary.

Question 15

The isomerization of citrate to isocitrate

Accepted Answer

A) is the reaction of the citric acid cycle that occurs spontaneously without enzymatic catalysis. 
B) protects cells from the toxic effects of arsenite ion. 
C) converts a tertiary alcohol,which cannot easily be oxidized,to a secondary alcohol that can be oxidized. 
D) is one major regulatory step for the citric acid cycle because it functions as a rate limiting step. 
E) A and B 
A) is the reaction of the citric acid cycle that occurs spontaneously without enzymatic catalysis. 
B) protects cells from the toxic effects of arsenite ion. 
C) converts a tertiary alcohol,which cannot easily be oxidized,to a secondary alcohol that can be oxidized. 
D) is one major regulatory step for the citric acid cycle because it functions as a rate limiting step. 
E) A and B

Question 16

Consider the following reaction which has a ∆G˚' ≈ +30 kJ/mol.
Malate + NAD+ → oxaloacetate + NADH + H+
In muscle cells,the reaction proceeds as written.Which of the following explains how the reaction occurs as written despite the positive value for $\Delta$G°'?

Accepted Answer

A) It is thermodynamically favored under standard conditions. 
B) In the cell,it is kinetically favored,even though it's thermodynamically unfavorable. 
C) The concentration of malate must be higher than oxaloacetate for this reaction to occur in the cell. 
D) [H+] must be higher in muscle than under standard conditions,thus altering ∆G˚ to ∆G˚'. 
E) None of the above 
A) It is thermodynamically favored under standard conditions. 
B) In the cell,it is kinetically favored,even though it's thermodynamically unfavorable. 
C) The concentration of malate must be higher than oxaloacetate for this reaction to occur in the cell. 
D) [H+] must be higher in muscle than under standard conditions,thus altering ∆G˚ to ∆G˚'. 
E) None of the above

Question 17

Which of the following statements correctly and most accurately describes the function of FAD in the pyruvate dehydrogenase enzyme complex?

Accepted Answer

A) NADH passes electrons to FAD to form FADH2. 
B) Lipoamide passes electrons through FADH2,which almost instantly passes them to NAD thus forming NADH. 
C) FADH2 donates electrons to lipoamide thus regenerating FAD. 
D) Lipoamide oxidizes NADH to NAD by passing electrons to FAD. 
E) NAD accepts electrons directly from lipoamide,which has gained them via oxidation of FADH2. 
A) NADH passes electrons to FAD to form FADH2. 
B) Lipoamide passes electrons through FADH2,which almost instantly passes them to NAD thus forming NADH. 
C) FADH2 donates electrons to lipoamide thus regenerating FAD. 
D) Lipoamide oxidizes NADH to NAD by passing electrons to FAD. 
E) NAD accepts electrons directly from lipoamide,which has gained them via oxidation of FADH2.

Question 18

Which of the following coenzymes is required by the pyruvate dehydrogenase complex for reoxidation of E3?

Accepted Answer

A) thiamine pyrophosphate 
B) pyridoxal phosphate 
C) coenzyme A 
D) FAD 
E) NAD+ 
A) thiamine pyrophosphate 
B) pyridoxal phosphate 
C) coenzyme A 
D) FAD 
E) NAD+

Question 19

Matching
Choose the correct answer from the list.Not all the answers will be used.

-The compound ______ is a structural analog and competitive inhibitor of the enzyme succinate dehydrogenase.

Accepted Answer

A)  oxaloacetate 
B)  malate synthase 
C)  malate 
D)  malonate 
E)  Krebs
F) aconitase
G) succinyl-CoA synthetase
H) α-ketoglutarate
I) carbon dioxide
J) malate dehydrogenase
K) isocitrate
L) succinate dehydrogenase 
A)  oxaloacetate 
B)  malate synthase 
C)  malate 
D)  malonate 
E)  Krebs
F) aconitase
G) succinyl-CoA synthetase
H) α-ketoglutarate
I) carbon dioxide
J) malate dehydrogenase
K) isocitrate
L) succinate dehydrogenase

Question 20

Which of the following causes pyruvate dehydrogenase kinase to catalyze the phosphorylation and inactivation of E1 in the pyruvate dehydrogenase complex?

Accepted Answer

A) elevated concentrations of NADH and ATP 
B) elevated concentrations of NAD+ and ADP 
C) insulin 
D) elevated concentrations of acetyl-CoA 
E) C and D 
A) elevated concentrations of NADH and ATP 
B) elevated concentrations of NAD+ and ADP 
C) insulin 
D) elevated concentrations of acetyl-CoA 
E) C and D

Exam 17: Citric Acid Cycle

Which of the following enzymatic reactions is favorable both under physiological conditions and under standard conditions?

Which of the following enzymes of the citric acid cycle is inhibited by ATP?

Matching Choose the correct answer from the list.Not all the answers will be used. -The enzyme ______ is part of the glyoxylate cycle that occurs in plants,bacteria,and fungi.

Matching Choose the correct answer from the list.Not all the answers will be used. -_____ and pyruvate can be combined in an ATP dependent reaction that regenerates one of the key intermediates in the citric acid cycle.

Which of the following would decrease activity of the citric acid cycle overall? (I)high concentration of NADH (II)high concentration of Ca2+ (III)high concentration of ATP (IV)high concentration of citrate

Bioinformatics has identified some enzymes used in the citric acid cycle in primitive bacteria.Once such a cycle utilized many of the citric acid cycle intermediates but occurred in the reverse direction.Researchers suspect which of the following based on this information?

Which of the following steps of the citric acid cycle conserves the energy of a high energy thioester bond?

If acetyl-CoA labeled with 14C,as shown in the figure to the right,were used as the substrate for the citric acid cycle,which of the following intermediates would be produced during the first round of the cycle?

The reaction catalyzed by _____ requires an enzyme bound flavin coenzyme.

Matching Choose the correct answer from the list.Not all the answers will be used. -______ is used in the first reaction of the citric acid cycle and regenerated upon completion of one turn of the citric acid cycle.

Which of the following represents a point of regulation for the citric acid cycle? (I)pyruvate dehydrogenase complex (II)aconitase (III)isocitrate dehydrogenase (IV)fumarase

One turn of the citric acid cycle generates

Which of the following utilizes intermediates of the citric acid cycle? (I)gluconeogenesis (II)amino acid biosynthesis (III)fatty acid oxidation (IV)glycolysis

Which of the following organisms does not utilize the glyxolate cycle?

The isomerization of citrate to isocitrate

Consider the following reaction which has a ∆G˚' ≈ +30 kJ/mol. Malate + NAD+ → oxaloacetate + NADH + H+ In muscle cells,the reaction proceeds as written.Which of the following explains how the reaction occurs as written despite the positive value for Δ\DeltaΔ G°'?

Which of the following statements correctly and most accurately describes the function of FAD in the pyruvate dehydrogenase enzyme complex?

Which of the following coenzymes is required by the pyruvate dehydrogenase complex for reoxidation of E3?

Matching Choose the correct answer from the list.Not all the answers will be used. -The compound ______ is a structural analog and competitive inhibitor of the enzyme succinate dehydrogenase.

Which of the following causes pyruvate dehydrogenase kinase to catalyze the phosphorylation and inactivation of E1 in the pyruvate dehydrogenase complex?

Introduction to the Chemistry of Life

Water

Nucleotides, nucleic Acids, and Genetic Information

Amino Acids

Proteins: Primary Structure

Proteins: Three-Dimensional Structure

Protein Function Part I: Myoglobin and Hemoglobin

Carbohydrates

Lipids and Biological Membranes

Membrane Transport

Enzyme Catalysis

Enzyme Kinetics, inhibition and Control

Biochemical Signaling

Introduction to Metabolism

Glucose Catabolism

Glycogen Metabolism and Gluconeogenesis

Electron Transport and Oxidative Phosphorylation

Photosynthesis

Lipid Metabolism

Amino Acid Metabolism

Mammalian Fuel Metabolism: Integration and Regulation

Nucleotide Metabolism

Nucleic Acid Structure

DNA Replication, repair and Recombination

Transcription and Rna Processing

Protein Synthesis

Regulation of Gene Expression

Filters

Which of the following would decrease activity of the citric acid cycle overall? (I)high concentration of NADH (II)high concentration of Ca²⁺ (III)high concentration of ATP (IV)high concentration of citrate

If acetyl-CoA labeled with ¹⁴C,as shown in the figure to the right,were used as the substrate for the citric acid cycle,which of the following intermediates would be produced during the first round of the cycle?

Consider the following reaction which has a ∆G˚' ≈ +30 kJ/mol. Malate + NAD⁺ → oxaloacetate + NADH + H⁺ In muscle cells,the reaction proceeds as written.Which of the following explains how the reaction occurs as written despite the positive value for $\Delta$ G^°^'?

Which of the following causes pyruvate dehydrogenase kinase to catalyze the phosphorylation and inactivation of E₁ in the pyruvate dehydrogenase complex?