Question 1

Which coenzyme in the citrate cycle is affected by arsenic?

Accepted Answer

A)  coenzyme A 
B)  thiamine pyrophosphate 
C)  dihydrolipopyl acetyltransferase 
D)  flavin adenine dinucleotide 
A)  coenzyme A 
B)  thiamine pyrophosphate 
C)  dihydrolipopyl acetyltransferase 
D)  flavin adenine dinucleotide

Question 2

The disease beriberi is a result of which vitamin deficiency?

Accepted Answer

A)  thiamine 
B)  pantothenic acid 
C)  riboflavin 
D)  niacin 
A)  thiamine 
B)  pantothenic acid 
C)  riboflavin 
D)  niacin

Question 3

Classify the reaction that occurs at step 4 in the reaction schematic of the pyruvate dehydrogenase reaction below.

Accepted Answer

A)  isomerization 
B)  addition 
C)  oxidation reduction 
D)  decarboxylation 
A)  isomerization 
B)  addition 
C)  oxidation reduction 
D)  decarboxylation

Question 4

When the citrate cycle is inhibited,which two metabolites are exported to the cytosol for fatty acid and cholesterol synthesis?

Accepted Answer

A)  malate and succinyl-CoA 
B)  succinyl-CoA and  -ketoglutarate 
C)    -ketoglutarate and citrate 
D)  citrate and malate 
A)  malate and succinyl-CoA 
B)  succinyl-CoA and  -ketoglutarate 
C)    -ketoglutarate and citrate 
D)  citrate and malate

Question 5

Predict the fate of acetyl-CoA and oxaloacetate when the citrate cycle is inhibited.

Accepted Answer

Acetyl Co-A is used in the cytosol for c

Question 6

Predict the fate of   -ketoglutarate when it is not used in the citrate cycle.

Accepted Answer

A)  cholesterol synthesis 
B)  heme synthesis 
C)  gluconeogenesis 
D)  amino acid synthesis 
A)  cholesterol synthesis 
B)  heme synthesis 
C)  gluconeogenesis 
D)  amino acid synthesis

Question 7

A low NADH to NAD+ ratio would activate which enzyme in the citrate cycle?

Accepted Answer

A)  succinyl-CoA synthetase 
B)  fumarase 
C)  citrate synthase 
D)  succinate dehydrogenase 
A)  succinyl-CoA synthetase 
B)  fumarase 
C)  citrate synthase 
D)  succinate dehydrogenase

Question 8

How would an increased level of acetyl-CoA be expected to affect the pyruvate dehydrogenase reaction?

Accepted Answer

A)  The pyruvate dehydrogenase kinase enzyme activity would increase, resulting in an inhibition of pyruvate dehydrogenase activity. 
B)  The last step of the pyruvate dehydrogenase reaction would be blocked, resulting in a decrease in activity. 
C)  The E1 subunit would be phosphorylated by pyruvate dehydrogenase kinase, and the catalytic activity of pyruvate dehydrogenase would decrease. 
D)  The pyruvate dehydrogenase phosphatase-1 enzyme would increase, resulting in pyruvate dehydrogenase activation at an accelerated rate. 
A)  The pyruvate dehydrogenase kinase enzyme activity would increase, resulting in an inhibition of pyruvate dehydrogenase activity. 
B)  The last step of the pyruvate dehydrogenase reaction would be blocked, resulting in a decrease in activity. 
C)  The E1 subunit would be phosphorylated by pyruvate dehydrogenase kinase, and the catalytic activity of pyruvate dehydrogenase would decrease. 
D)  The pyruvate dehydrogenase phosphatase-1 enzyme would increase, resulting in pyruvate dehydrogenase activation at an accelerated rate.

Question 9

Which enzyme requires CoASH to produce acetyl-CoA?

Accepted Answer

A)  pyruvate dehydrogenase 
B)  citrate synthase 
C)  isocitrate dehydrogenase 
D)    -ketoglutarate dehydrogenase 
A)  pyruvate dehydrogenase 
B)  citrate synthase 
C)  isocitrate dehydrogenase 
D)    -ketoglutarate dehydrogenase

Question 10

Corn-rich diets in Europe in the 1700s resulted in the disease pellagra.Though Mexico also had a corn-rich diet at the time,this disease was rare there.Propose a reason for this observation.

Accepted Answer

Pellagra is the result of a niacin defic

Question 11

Use the overall net reaction of the citrate cycle to explain why excess NADH inhibits the pyruvate dehydrogenase reaction.

Accepted Answer

NADH is a product in the balanced citrat

Question 12

Describe the fate of NADH and FADH2 produced in the citrate cycle.

Accepted Answer

NADH and FADH₂ enter the electr

Question 13

How is the pyruvate dehydrogenase reaction regulated?

Accepted Answer

A)  pH and enzyme conformation 
B)  pH and the protonation state of the active site 
C)  allosteric control and covalent modification 
D)  product inhibition 
A)  pH and enzyme conformation 
B)  pH and the protonation state of the active site 
C)  allosteric control and covalent modification 
D)  product inhibition

Question 14

The reaction catalyzed by __________ is likely to be reversible under cellular conditions according to the   .

Accepted Answer

A)  malate dehydrogenase 
B)  citrate synthase 
C)  succinate dehydrogenase 
D)    -ketoglutarate dehydrogenase 
A)  malate dehydrogenase 
B)  citrate synthase 
C)  succinate dehydrogenase 
D)    -ketoglutarate dehydrogenase

Question 15

The   
of the conversion from malate to oxaloacetate in the last reaction of the citrate cycle is very large,indicating this reaction is not thermodynamically favorable.Propose an explanation for how this reaction can proceed in the forward direction despite the very positive   
value.

Accepted Answer

The oxaloacetate concentrations are kept

Question 16

High levels of ATP would result in the inhibition of which enzyme in the citrate cycle?

Accepted Answer

A)  succinate dehydrogenase 
B)  isocitrate dehydrogenase 
C)  malate dehydrogenase 
D)  fumarase 
A)  succinate dehydrogenase 
B)  isocitrate dehydrogenase 
C)  malate dehydrogenase 
D)  fumarase

Question 17

A high NADH to NAD+ ratio would inhibit which enzyme in the citrate cycle?

Accepted Answer

A)  succinate dehydrogenase 
B)  succinyl-CoA synthetase 
C)  aconitase 
D)  isocitrate dehydrogenase 
A)  succinate dehydrogenase 
B)  succinyl-CoA synthetase 
C)  aconitase 
D)  isocitrate dehydrogenase

Question 18

A high concentration of which molecule would inhibit citrate synthase in the citrate cycle?

Accepted Answer

A)  AMP 
B)  ADP 
C)  NAD+ 
D)  ATP 
A)  AMP 
B)  ADP 
C)  NAD+ 
D)  ATP

Question 19

Regeneration of NAD+ and FAD inside the mitochondrial matrix is required because

Accepted Answer

A)  anabolic reactions generally require them. 
B)  they produce GDP through the citrate cycle. 
C)  they transport pyruvate through the matrix. 
D)  they maintain flux through the citrate cycle. 
A)  anabolic reactions generally require them. 
B)  they produce GDP through the citrate cycle. 
C)  they transport pyruvate through the matrix. 
D)  they maintain flux through the citrate cycle.

Question 20

Classify the reaction that occurs at step 5 in the reaction schematic of the pyruvate dehydrogenase reaction below.

Accepted Answer

A)  isomerization 
B)  addition 
C)  oxidation reduction 
D)  decarboxylation 
A)  isomerization 
B)  addition 
C)  oxidation reduction 
D)  decarboxylation

Exam 10: The Citrate Cycle

Which coenzyme in the citrate cycle is affected by arsenic?

The disease beriberi is a result of which vitamin deficiency?

Classify the reaction that occurs at step 4 in the reaction schematic of the pyruvate dehydrogenase reaction below.

When the citrate cycle is inhibited,which two metabolites are exported to the cytosol for fatty acid and cholesterol synthesis?

Predict the fate of acetyl-CoA and oxaloacetate when the citrate cycle is inhibited.

Predict the fate of -ketoglutarate when it is not used in the citrate cycle.

A low NADH to NAD+ ratio would activate which enzyme in the citrate cycle?

How would an increased level of acetyl-CoA be expected to affect the pyruvate dehydrogenase reaction?

Which enzyme requires CoASH to produce acetyl-CoA?

Corn-rich diets in Europe in the 1700s resulted in the disease pellagra.Though Mexico also had a corn-rich diet at the time,this disease was rare there.Propose a reason for this observation.

Use the overall net reaction of the citrate cycle to explain why excess NADH inhibits the pyruvate dehydrogenase reaction.

Describe the fate of NADH and FADH2 produced in the citrate cycle.

How is the pyruvate dehydrogenase reaction regulated?

The reaction catalyzed by __________ is likely to be reversible under cellular conditions according to the .

The of the conversion from malate to oxaloacetate in the last reaction of the citrate cycle is very large,indicating this reaction is not thermodynamically favorable.Propose an explanation for how this reaction can proceed in the forward direction despite the very positive value.

High levels of ATP would result in the inhibition of which enzyme in the citrate cycle?

A high NADH to NAD+ ratio would inhibit which enzyme in the citrate cycle?

A high concentration of which molecule would inhibit citrate synthase in the citrate cycle?

Regeneration of NAD+ and FAD inside the mitochondrial matrix is required because

Classify the reaction that occurs at step 5 in the reaction schematic of the pyruvate dehydrogenase reaction below.

Principles of Biochemistry

Physical Biochemistry: Energy Conversion,water,and Membranes

Nucleic Acid Structure and Function

Protein Structure

Methods in Protein Biochemistry

Protein Function

Enzyme Mechanisms

Cell Signaling Systems

Glycolysis: a Paradigm of Metabolic Regulation

Oxidative Phosphorylation

Photosynthesis

Carbohydrate Structure and Function

Carbohydrate Metabolism

Lipid Structure and Function

Lipid Metabolism

Amino Acid Metabolism

Nucleotide Metabolism

Metabolic Integration

Dna Replication, repair, and Recombination

Rna Synthesis, processing, and Gene Silencing

Protein Synthesis, posttranslational Modification, and Transport

Gene Regulation

Filters

A low NADH to NAD⁺ ratio would activate which enzyme in the citrate cycle?

Describe the fate of NADH and FADH₂ produced in the citrate cycle.

A high NADH to NAD⁺ ratio would inhibit which enzyme in the citrate cycle?

Regeneration of NAD⁺ and FAD inside the mitochondrial matrix is required because