Question 1

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 dehydrogenaseE) C) and D)
F) B) and D)

Question 2

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

Accepted Answer

A)   AMP
B)   ADP
C)   NAD+
D)   ATPE) A) and D)
F) B) and D)

Question 3

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 4

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 5

The disease beriberi is a result of which vitamin deficiency?

Accepted Answer

A)   thiamine
B)   pantothenic acid
C)   riboflavin
D)   niacinE) All of the above
F) A) and B)

Question 6

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 malateE) A) and B)
F) A) and C)

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 dehydrogenaseE) All of the above
F) A) and B)

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.E) B) and C)
F) None of the above

Question 9

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.E) A) and D)
F) B) and C)

Question 10

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 11

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 dehydrogenaseE) A) and C)
F) B) and D)

Question 12

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 13

Which enzyme requires CoASH to produce acetyl-CoA?

Accepted Answer

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

Question 14

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

Accepted Answer

NADH and FADH₂ enter the electr...

Question 15

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)   fumaraseE) A) and B)
F) A) and C)

Question 16

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 synthesisE) C) and D)
F) B) and C)

Question 17

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 inhibitionE) All of the above
F) A) and D)

Question 18

Which coenzyme in the citrate cycle is affected by arsenic?

Accepted Answer

A)   coenzyme A
B)   thiamine pyrophosphate
C)   dihydrolipopyl acetyltransferase
D)   flavin adenine dinucleotideE) B) and C)
F) None of the above

Question 19

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)   decarboxylationE) A) and B)
F) All of the above

Question 20

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)   decarboxylationE) None of the above
F) C) and D)

Exam 10: The Citrate Cycle

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

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

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

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

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

Correct AnswerverifiedAcetyl Co-A is used in the cytosol for c...View AnswerShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Which coenzyme in the citrate cycle is affected by arsenic?

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

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Which enzyme requires CoASH to produce acetyl-CoA?

Correct AnswerverifiedShow Answer

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.

Correct AnswerverifiedThe oxaloacetate concentrations are kept...View AnswerShow Answer

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

Correct AnswerverifiedNADH and FADH2 enter the electr...View AnswerShow Answer

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.

Correct AnswerverifiedPellagra is the result of a niacin defic...View AnswerShow Answer

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

Correct AnswerverifiedShow Answer

The disease beriberi is a result of which vitamin deficiency?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

How is the pyruvate dehydrogenase reaction regulated?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedNADH is a product in the balanced citrat...View AnswerShow Answer

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

Correct AnswerverifiedShow Answer

Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
verified
Acetyl Co-A is used in the cytosol for c...
View Answer

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

Correct Answer
verified

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

Correct Answer
verified

Correct Answer
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Correct Answer
verified

Correct Answer
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Correct Answer
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The oxaloacetate concentrations are kept...
View Answer

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

Correct Answer
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NADH and FADH₂ enter the electr...
View Answer

Correct Answer
verified
Pellagra is the result of a niacin defic...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
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NADH is a product in the balanced citrat...
View Answer

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

Correct Answer
verified