Question 1

The reaction in which malate is oxidized to oxaloacetate is not thermodynamically favored.It takes place because

Accepted Answer

A)  it is coupled to ATP hydrolysis. 
B)  it involves substrate-level phosphorylation. 
C)  the product is continuously used up in the next reaction of the cycle, which is thermodynamically favored. 
D)  it is coupled to a strong reduction. 
A)  it is coupled to ATP hydrolysis. 
B)  it involves substrate-level phosphorylation. 
C)  the product is continuously used up in the next reaction of the cycle, which is thermodynamically favored. 
D)  it is coupled to a strong reduction.

Question 2

The "energy charge" in a cell is important in the control of metabolism.

Accepted Answer

A) True 
 B)False

Question 3

The acetyl group is carried on lipoic acid as

Accepted Answer

A)  an alcohol. 
B)  a thioester. 
C)  a phosphoanhydride. 
D)  an amide. 
A)  an alcohol. 
B)  a thioester. 
C)  a phosphoanhydride. 
D)  an amide.

Question 4

Which of the following is not a reaction occurring during oxidative decarboxylation of pyruvate?

Accepted Answer

A)  Removal of CO2. 
B)  Oxidation of an acetate group. 
C)  Addition of Coenzyme A to a 2-carbon fragment. 
D)  Reduction of NAD+ 
E)  All of these reactions take place during oxidative decarboxylation. 
A)  Removal of CO2. 
B)  Oxidation of an acetate group. 
C)  Addition of Coenzyme A to a 2-carbon fragment. 
D)  Reduction of NAD+ 
E)  All of these reactions take place during oxidative decarboxylation.

Question 5

When the citric acid cycle is not functioning,the most common fate of acetyl-CoA from sugar metabolism in humans is the formation of fatty acids or cholesterol.

Accepted Answer

A) True 
 B)False

Question 6

There is a cyclic reaction in which pyruvate becomes oxaloacetate.The oxaloacetate is converted to malate and then back to pyruvate.This cycle is important because:

Accepted Answer

A)  There is no net use or fixation of CO2 in this cycle. 
B)  NADH is converted to NADPH in this cycle. 
C)  There is no net oxidation or reduction in this cycle. 
D)  NADPH is converted to NADH in this cycle. 
E)  This is actually a wasteful pathway with no practical use. 
A)  There is no net use or fixation of CO2 in this cycle. 
B)  NADH is converted to NADPH in this cycle. 
C)  There is no net oxidation or reduction in this cycle. 
D)  NADPH is converted to NADH in this cycle. 
E)  This is actually a wasteful pathway with no practical use.

Question 7

Most of the products of the catabolism of sugars,fats and amino acids enter the citric acid cycle as:

Accepted Answer

A)  pyruvate 
B)  acetyl-CoA 
C)  malate 
D)  all of these 
E)  none of these 
A)  pyruvate 
B)  acetyl-CoA 
C)  malate 
D)  all of these 
E)  none of these

Question 8

The enzyme "aconitase" is also known as "condensing enzyme"

Accepted Answer

A) True 
 B)False

Question 9

The reaction of the citric acid cycle that does not take place in the mitochondrial matrix is the one catalyzed by:

Accepted Answer

A)  fumarase 
B)  citrate synthase 
C)  isocitrate dehydrogenase 
D)  succinate dehydrogenase 
E)  All of these reactions take place in the matrix 
A)  fumarase 
B)  citrate synthase 
C)  isocitrate dehydrogenase 
D)  succinate dehydrogenase 
E)  All of these reactions take place in the matrix

Question 10

Exhibit 19A   The following compounds are all intermediates in the citric acid cycle.
Refer to Exhibit 19A.Which intermediate is formed from acetyl-CoA and oxaloacetate.

Accepted Answer

A)  1 
B)  2 
C)  3 
D)  4 
E)  5 
A)  1 
B)  2 
C)  3 
D)  4 
E)  5

Question 11

Which of the following cannot cross the inner mitochondrial membrane?

Accepted Answer

A)  malate 
B)  phosphoenolpyruvate 
C)  succinyl-CoA 
D)  oxaloacetate 
A)  malate 
B)  phosphoenolpyruvate 
C)  succinyl-CoA 
D)  oxaloacetate

Question 12

Lipoic acid is a required vitamin in the human diet.

Accepted Answer

A) True 
 B)False

Question 13

Exhibit 19A   The following compounds are all intermediates in the citric acid cycle.
Refer to Exhibit 19A.Which intermediate releases CO2 concurrent with oxidation?

Accepted Answer

A)  1 
B)  2 
C)  3 
D)  Both 1 and 3 
E)  Both 2 and 3 
A)  1 
B)  2 
C)  3 
D)  Both 1 and 3 
E)  Both 2 and 3

Question 14

Which of the following enzymes is the only membrane-bound enzyme in the citric acid cycle?

Accepted Answer

A)  Aconitase. 
B)  IsoCitrate Dehydrogenase. 
C)  Succinate Dehydrogenase. 
D)  Malate Dehydrogenase. 
E)  Alpha-Ketoglutarate Dehydrogenase complex. 
A)  Aconitase. 
B)  IsoCitrate Dehydrogenase. 
C)  Succinate Dehydrogenase. 
D)  Malate Dehydrogenase. 
E)  Alpha-Ketoglutarate Dehydrogenase complex.

Question 15

When acetyl-CoA reacts with oxaloacetate to form citrate

Accepted Answer

A)  a new carbon-carbon bond is formed 
B)  an oxidative decarboxylation reaction takes place 
C)  a dehydration reaction takes place 
D)  a rearrangement takes place 
A)  a new carbon-carbon bond is formed 
B)  an oxidative decarboxylation reaction takes place 
C)  a dehydration reaction takes place 
D)  a rearrangement takes place

Question 16

Fluorine is related to the citric acid cycle because:

Accepted Answer

A)  fluoroacetyl-CoA is also a substrate for citrate synthase 
B)  fluoroacetate, found in poisonous plants, acts as an inhibitor of aconitase 
C)  fluorocitrate acts as a potent inhibitor of the citric acid cycle 
D)  all of these 
A)  fluoroacetyl-CoA is also a substrate for citrate synthase 
B)  fluoroacetate, found in poisonous plants, acts as an inhibitor of aconitase 
C)  fluorocitrate acts as a potent inhibitor of the citric acid cycle 
D)  all of these

Question 17

The glyoxylate pathway bypasses part of the citric acid cycle by converting isocitrate to glyoxylate and

Accepted Answer

A)  a-ketoglutarate 
B)  fumarate 
C)  succinyl-CoA 
D)  succinate 
A)  a-ketoglutarate 
B)  fumarate 
C)  succinyl-CoA 
D)  succinate

Question 18

In the glyoxylate cycle,acetyl-CoA reacts with glyoxylate to produce

Accepted Answer

A)  succinyl-CoA 
B)  succinate 
C)  fumarate 
D)  malate 
A)  succinyl-CoA 
B)  succinate 
C)  fumarate 
D)  malate

Question 19

Glyoxysomes are named for the fact that they contain the glyoxylate pathway.

Accepted Answer

A) True 
 B)False

Question 20

Exhibit 19A   The following compounds are all intermediates in the citric acid cycle.
Refer to Exhibit 19A.Which intermediate does FAD oxidize?

Accepted Answer

A)  2 
B)  3 
C)  4 
D)  5 
E)  More than one of these is oxidized by FAD. 
A)  2 
B)  3 
C)  4 
D)  5 
E)  More than one of these is oxidized by FAD.

Exam 19: The Citric Acid Cycle

The reaction in which malate is oxidized to oxaloacetate is not thermodynamically favored.It takes place because

The "energy charge" in a cell is important in the control of metabolism.

The acetyl group is carried on lipoic acid as

Which of the following is not a reaction occurring during oxidative decarboxylation of pyruvate?

When the citric acid cycle is not functioning,the most common fate of acetyl-CoA from sugar metabolism in humans is the formation of fatty acids or cholesterol.

There is a cyclic reaction in which pyruvate becomes oxaloacetate.The oxaloacetate is converted to malate and then back to pyruvate.This cycle is important because:

Most of the products of the catabolism of sugars,fats and amino acids enter the citric acid cycle as:

The enzyme "aconitase" is also known as "condensing enzyme"

The reaction of the citric acid cycle that does not take place in the mitochondrial matrix is the one catalyzed by:

Exhibit 19A The following compounds are all intermediates in the citric acid cycle. Refer to Exhibit 19A.Which intermediate is formed from acetyl-CoA and oxaloacetate.

Which of the following cannot cross the inner mitochondrial membrane?

Lipoic acid is a required vitamin in the human diet.

Exhibit 19A The following compounds are all intermediates in the citric acid cycle. Refer to Exhibit 19A.Which intermediate releases CO2 concurrent with oxidation?

Which of the following enzymes is the only membrane-bound enzyme in the citric acid cycle?

When acetyl-CoA reacts with oxaloacetate to form citrate

Fluorine is related to the citric acid cycle because:

The glyoxylate pathway bypasses part of the citric acid cycle by converting isocitrate to glyoxylate and

In the glyoxylate cycle,acetyl-CoA reacts with glyoxylate to produce

Glyoxysomes are named for the fact that they contain the glyoxylate pathway.

Exhibit 19A The following compounds are all intermediates in the citric acid cycle. Refer to Exhibit 19A.Which intermediate does FAD oxidize?

Biochemistry and the Organization of Cells

Water: The Solvent for Biochemical Reactions

Amino Acids and Peptides

The Three-Dimensional Structure of Proteins

Protein Purification and Characterization Techniques

The Behavior of Proteins: Enzymes

The Behavior of Proteins: Enzymes, Mechanisms, and Control

Lipids and Proteins Are Associated in Biological Membranes

Nucleic Acids: How Structure Conveys Information

Biosynthesis of Nucleic Acids: Replication

Transcription of the Genetic Code: Biosynthesis of Rna

Protein Synthesis: Translation of the Genetic Message

Nucleic Acid Biotechnology Techniques

Viruses, Cancer, and Immunology

The Importance of Energy Changes and Electron Transfer in Metabolism

Carbohydrates

Glycolysis

Storage Mechanisms and Control in Carbohydrate Metabolism

Electron Transport and Oxidative Phosphorylation

Lipid Metabolism

Photosynthesis

The Metabolism of Nitrogen

Integration of Metabolism: Cellular Signaling

Filters

Exhibit 19A The following compounds are all intermediates in the citric acid cycle. Refer to Exhibit 19A.Which intermediate releases CO₂ concurrent with oxidation?