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 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 A

Question 3

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 E

Question 4

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 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

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 7

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 8

In eukaryotes, the citric acid cycle occurs in the _____ and therefore requires that reactants of the citric acid cycle be transported from the _____.

Accepted Answer

A) cytosol; mitochondrial matrix 
B) mitochondrial matrix; cytosol 
C) endoplasmic reticulum; mitochondrial matrix 
D) inner mitochondrial membrane; mitochondrial matrix 
E) outer mitochondrial membrane; cytosol 
A) cytosol; mitochondrial matrix 
B) mitochondrial matrix; cytosol 
C) endoplasmic reticulum; mitochondrial matrix 
D) inner mitochondrial membrane; mitochondrial matrix 
E) outer mitochondrial membrane; cytosol

Question 9

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 10

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 11

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 12

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 13

Matching 
Choose the correct answer from the list. Not all the answers will be used.
-The name of a citric acid cycle intermediate that is derived from the Latin word for "apple" 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 14

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 15

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 16

Which of the following uses inherent length and flexibility to facilitate transfer of an acetyl group?

Accepted Answer

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

Question 17

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 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

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 20

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

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 enzymatic reactions is favorable both under physiological conditions and under standard conditions?

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

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

How many electrons are transferred from one acetyl group during 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

In eukaryotes, the citric acid cycle occurs in the _____ and therefore requires that reactants of the citric acid cycle be transported from the _____.

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

The isomerization of citrate to isocitrate

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?

Matching Choose the correct answer from the list. Not all the answers will be used. -The name of a citric acid cycle intermediate that is derived from the Latin word for "apple" is ______.

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

Which of the following uses inherent length and flexibility to facilitate transfer of an acetyl group?

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

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

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°'?

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?

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

Glycogen Metabolism and Gluconeogenesis

Glucose Catabolism

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

Translation

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

In eukaryotes, the citric acid cycle occurs in the _ and therefore requires that reactants of the citric acid cycle be transported from the _.

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^°^'?