Question 1

Which of the following is an intermediate between citrate and isocitrate in the citric acid cycle?

Accepted Answer

A) succinyl-CoA 
B) citryl-CoA 
C) oxalosuccinate 
D) succinyl-phosphate 
E) cis-aconitate 
A) succinyl-CoA 
B) citryl-CoA 
C) oxalosuccinate 
D) succinyl-phosphate 
E) cis-aconitate E

Question 2

Which of the following enzymes catalyzes a reaction with the pictured compound as an intermediate?

Accepted Answer

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

Question 3

An individual with a shortage of B vitamins (which include thiamine and riboflavin)may feel fatigued as a result of decreased pyruvate dehydrogenase activity.Which of the following would be TRUE regarding this shortage?

Accepted Answer

A) The amount of acetyl CoA produced from carbohydrate metabolism that enters the citric acid cycle would be decreased. 
B) A decrease in the amount of NADH would likely decrease activity of citrate synthase. 
C) Flux through the citric acid cycle would cease until adequate pyruvate is available. 
D) none of the above 
E) all of the above 
A) The amount of acetyl CoA produced from carbohydrate metabolism that enters the citric acid cycle would be decreased. 
B) A decrease in the amount of NADH would likely decrease activity of citrate synthase. 
C) Flux through the citric acid cycle would cease until adequate pyruvate is available. 
D) none of the above 
E) all of the above A

Question 4

Which of the following is oxidized by a multienzyme complex that requires five different coenzymes?

Accepted Answer

A) 
  
B) 
  
C) 
  
D) A and B 
E) A,B,and C 
A) 
  
B) 
  
C) 
  
D) A and B 
E) A,B,and C

Question 5

How many electrons are transferred from one acetyl group during the citric acid cycle?

Accepted Answer

A) 2 
B) 4 
C) 6 
D) 8 
E) 10 
A) 2 
B) 4 
C) 6 
D) 8 
E) 10

Question 6

E2 of the pyruvate dehydrogenase complex contains a lipoyl group that is covalently attached via an amide linkage to a ______ residue on the enzyme?

Accepted Answer

A) tyrosine 
B) serine 
C) lysine 
D) arginine 
E) cysteine 
A) tyrosine 
B) serine 
C) lysine 
D) arginine 
E) cysteine

Question 7

Which reaction below produces GTP in the citric acid cycle?

Accepted Answer

A) "isocitrate $\to$ $\alpha$-ketoglutarate" 
B) "$\alpha$-ketoglutarate $\to$ succinyl CoA" 
C) "succinyl CoA $\to$ succinate" 
D) "fumarate $\to$ malate" 
E) "malate $\to$ oxaloacetate" 
A) "isocitrate $\to$ $\alpha$-ketoglutarate" 
B) "$\alpha$-ketoglutarate $\to$ succinyl CoA" 
C) "succinyl CoA $\to$ succinate" 
D) "fumarate $\to$ malate" 
E) "malate $\to$ oxaloacetate"

Question 8

Which of the following coenzymes is required by E1 of the pyruvate dehydrogenase complex for catalytic activity?

Accepted Answer

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

Question 9

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

-The citric acid cycle is also called the ______ 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 10

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

-______ catalyzes a substrate-level phosphorylation reaction within 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

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

-______ is the first compound that is oxidized 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 12

Which of the following is(are)TRUE concerning the metabolic reaction shown below?
 Pyruvate + NAD+ + CoA-SH SYMBOL 174 \f "Symbol" Acetyl-CoA + NADH + H+  + CO2
(I)The enzyme that catalyzes this reaction contains a pyridoxal phosphate prosthetic group.
(II)This reaction is an oxidative decarboxylation.
(III)The enzyme that catalyzes this metabolic conversion is activated by high concentrations of ATP.

Accepted Answer

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

Question 13

Considering the reactions within the citric acid cycle,which of the following molecules will be produced from the intermediate pictured on the right?

Accepted Answer

A) citrate 
B) isocitriate 
C) succinate 
D) succinyl-CoA 
E) α-ketoglutarate 
A) citrate 
B) isocitriate 
C) succinate 
D) succinyl-CoA 
E) α-ketoglutarate

Question 14

Which of the following amino acid residues facilitates the transfer of a phosphate group in the reaction producing succinate and GTP?

Accepted Answer

A) aspartate 
B) glutamate 
C) histidine 
D) lysine 
E) serine 
A) aspartate 
B) glutamate 
C) histidine 
D) lysine 
E) serine

Question 15

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

-A membrane-bound enzyme of the citric acid cycle that catalyzes an oxidation reaction is ______.

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 16

The figure at right represents an intermediate in the reaction catalyzed by which of the following enzymes?

Accepted Answer

A) enolase 
B) aldolase 
C) pyruvate decarboxylase 
D) glyceraldehyde-3-phosphate dehydrogenase 
E) lactate dehydrogenase 
A) enolase 
B) aldolase 
C) pyruvate decarboxylase 
D) glyceraldehyde-3-phosphate dehydrogenase 
E) lactate dehydrogenase

Question 17

Condensation of ____ with oxaloacetate yield citrate.

Accepted Answer

A) acetyl-CoA 
B) α-ketoglutarate 
C) isocitrate 
D) citrophosphate 
E) oxalosuccinate 
A) acetyl-CoA 
B) α-ketoglutarate 
C) isocitrate 
D) citrophosphate 
E) oxalosuccinate

Question 18

Which of the following is TRUE regarding the discovery of the citric acid cycle?
(I)One of the first discoveries was the involvement of coenzyme A in the production of GTP.
(II)Krebs had knowledge of the sequence of reactions before he was able to demonstrate the link of the cycle to glucose metabolism.
(III)The citric acid cycle was the first cyclic pathway discovered.
(IV)Krebs demonstrated the involvement of the citric acid cycle in oxidation of amino acid and fatty acids.

Accepted Answer

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

Question 19

Which of the following best describes the importance of the citric acid cycle as a central pathway of metabolism?

Accepted Answer

A) It allows recovery of energy from carbohydrates only. 
B) It allows recovery of energy from fatty acids only. 
C) It allows recovery of energy from amino acids only. 
D) It allows recovery of energy from several metabolic fuels that are broken down to acetyl-CoA. 
E) A and B 
A) It allows recovery of energy from carbohydrates only. 
B) It allows recovery of energy from fatty acids only. 
C) It allows recovery of energy from amino acids only. 
D) It allows recovery of energy from several metabolic fuels that are broken down to acetyl-CoA. 
E) A and B

Question 20

The reaction catalyzed by pyruvate carboxylase is an example of a(n)______ reaction because it replenishes the citric acid cycle intermediates that have been siphoned off for use in other reactions.

Accepted Answer

A) amphibolic 
B) amphipathic 
C) anaplerotic 
D) cataplerotic 
E) none of the above 
A) amphibolic 
B) amphipathic 
C) anaplerotic 
D) cataplerotic 
E) none of the above

Exam 17: Citric Acid Cycle

Which of the following is an intermediate between citrate and isocitrate in the citric acid cycle?

Which of the following enzymes catalyzes a reaction with the pictured compound as an intermediate?

An individual with a shortage of B vitamins (which include thiamine and riboflavin)may feel fatigued as a result of decreased pyruvate dehydrogenase activity.Which of the following would be TRUE regarding this shortage?

Which of the following is oxidized by a multienzyme complex that requires five different coenzymes?

How many electrons are transferred from one acetyl group during the citric acid cycle?

E2 of the pyruvate dehydrogenase complex contains a lipoyl group that is covalently attached via an amide linkage to a ______ residue on the enzyme?

Which reaction below produces GTP in the citric acid cycle?

Which of the following coenzymes is required by E1 of the pyruvate dehydrogenase complex for catalytic activity?

Matching Choose the correct answer from the list.Not all the answers will be used. -The citric acid cycle is also called the ______ cycle.

Matching Choose the correct answer from the list.Not all the answers will be used. -______ catalyzes a substrate-level phosphorylation reaction within the citric acid cycle.

Matching Choose the correct answer from the list.Not all the answers will be used. -______ is the first compound that is oxidized in the citric acid cycle.

Considering the reactions within the citric acid cycle,which of the following molecules will be produced from the intermediate pictured on the right?

Which of the following amino acid residues facilitates the transfer of a phosphate group in the reaction producing succinate and GTP?

Matching Choose the correct answer from the list.Not all the answers will be used. -A membrane-bound enzyme of the citric acid cycle that catalyzes an oxidation reaction is ______.

The figure at right represents an intermediate in the reaction catalyzed by which of the following enzymes?

Condensation of ____ with oxaloacetate yield citrate.

Which of the following best describes the importance of the citric acid cycle as a central pathway of metabolism?

The reaction catalyzed by pyruvate carboxylase is an example of a(n)______ reaction because it replenishes the citric acid cycle intermediates that have been siphoned off for use in other reactions.

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

E₂of the pyruvate dehydrogenase complex contains a lipoyl group that is covalently attached via an amide linkage to a ______ residue on the enzyme?

Which of the following coenzymes is required by E₁ of the pyruvate dehydrogenase complex for catalytic activity?