Question 1

The primary function of NAD+ in the citrate cycle is that it

Accepted Answer

A)  functions as an electron donor. 
B)  is oxidized to produce GTP. 
C)  acts as an electron acceptor. 
D)  phosphorylates ADP. 
A)  functions as an electron donor. 
B)  is oxidized to produce GTP. 
C)  acts as an electron acceptor. 
D)  phosphorylates ADP.

Question 2

Coenzyme A does not readily cross the cell membrane. However, coenzyme A functions as an acyl carrier in the citrate cycle in the mitochondrial matrix. Explain how coenzyme A crosses the cell membrane to participate in the citrate cycle.

Accepted Answer

Coenzyme A is degraded in the gut to pan

Question 3

ATP regulates the citrate cycle but is not found as a direct product of any of the reactions. Explain how ATP regulates the cycle and identify the enzymes that ATP regulates.

Accepted Answer

ATP is an example of feedback inhibition

Question 4

Identify the E1 subunit in the reaction schematic of the pyruvate dehydrogenase reaction below.

Accepted Answer

A)  pyruvate dehydrogenase 
B)  dihydrolipoyl dehydrogenase 
C)  dihydrolipopyl acetyltransferase 
D)  flavin adenine dinucleotide 
A)  pyruvate dehydrogenase 
B)  dihydrolipoyl dehydrogenase 
C)  dihydrolipopyl acetyltransferase 
D)  flavin adenine dinucleotide

Question 5

The reaction catalyzed by is likely to be reversible under cellular conditions according to the $\Delta$G$\degree$' .

Accepted Answer

A)  "malate dehydrogenase" 
B)  "citrate synthase" 
C)  "succinate dehydrogenase" 
D)  "$\alpha$-ketoglutarate dehydrogenase" 
A)  "malate dehydrogenase" 
B)  "citrate synthase" 
C)  "succinate dehydrogenase" 
D)  "$\alpha$-ketoglutarate dehydrogenase"

Question 6

Compare and contrast the anaplerotic nature of the pyruvate carboxylase reaction and the phosphoenolpyruvate carboxylase reaction.

Accepted Answer

Both reactions help replenish oxaloaceta

Question 7

Which of the following is a reactant in the net reaction of the citrate cycle?

Accepted Answer

A)  CO2 
B)  H2O 
C)  GTP 
D)  CoA 
A)  CO2 
B)  H2O 
C)  GTP 
D)  CoA

Question 8

Explain the effect a high concentration of NADH has on the citrate cycle.

Accepted Answer

High NADH implies that the cell does not

Question 9

In two turns of the citrate cycle, how many electrons are transferred from the citrate cycle intermediates to NAD+ and FAD?

Accepted Answer

A)  4 
B)  8 
C)  12 
D)  16 
A)  4 
B)  8 
C)  12 
D)  16

Question 10

Which citrate cycle intermediate is siphoned off the citrate cycle during starvation?

Accepted Answer

A)  "succinyl-CoA" 
B)  "malate" 
C)  "$\alpha$-ketoglutarate" 
D)  "fumarate" 
A)  "succinyl-CoA" 
B)  "malate" 
C)  "$\alpha$-ketoglutarate" 
D)  "fumarate"

Question 11

You exercise vigorously for 30 minutes. Which chemical compounds would you expect to be elevated that would affect the regulation of pyruvate dehydrogenase? State the substances and explain how they would affect the regulation.

Accepted Answer

Muscle contraction results in an increas

Question 12

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 13

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 14

Which reaction in the citrate cycle produces NADH?

Accepted Answer

A)  4 
B)  5 
C)  6 
D)  7 
A)  4 
B)  5 
C)  6 
D)  7

Question 15

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 16

Explain what redox reaction $\Delta$E$\degree$'  values mean regarding spontaneity. How does the spontaneity affect the arrangement of multiple redox reactions in a linked metabolic pathway?

Accepted Answer

Redox reactions with positive @#LAT-DLM& E@#LAT-DLM&^'</

Question 17

Which anaplerotic reactions do plants, yeast, and bacteria use to generate oxaloacetate?

Accepted Answer

A)  pyruvate carboxylase 
B)  malic enzyme 
C)  phosphoenolpyruvate carboxylase 
D)  malate dehydrogenase 
A)  pyruvate carboxylase 
B)  malic enzyme 
C)  phosphoenolpyruvate carboxylase 
D)  malate dehydrogenase

Question 18

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

Question 19

Arsenite affects the lipoamide coenzymes of the pyruvate dehydrogenase reaction by

Accepted Answer

A)  acting as a competitive inhibitor. 
B)  covalently modifying the coenzyme. 
C)  being a noncompetitive inhibitor. 
D)  modifying the coenzyme through electrostatic interactions. 
A)  acting as a competitive inhibitor. 
B)  covalently modifying the coenzyme. 
C)  being a noncompetitive inhibitor. 
D)  modifying the coenzyme through electrostatic interactions.

Question 20

How would a high NADH to NAD+ ratio be expected to affect the pyruvate dehydrogenase reaction?

Accepted Answer

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

Exam 10: The Citrate Cycle

The primary function of NAD+ in the citrate cycle is that it

Coenzyme A does not readily cross the cell membrane. However, coenzyme A functions as an acyl carrier in the citrate cycle in the mitochondrial matrix. Explain how coenzyme A crosses the cell membrane to participate in the citrate cycle.

ATP regulates the citrate cycle but is not found as a direct product of any of the reactions. Explain how ATP regulates the cycle and identify the enzymes that ATP regulates.

Identify the E1 subunit in the reaction schematic of the pyruvate dehydrogenase reaction below.

The reaction catalyzed by is likely to be reversible under cellular conditions according to the Δ\DeltaΔ G °\degree° ' .

Compare and contrast the anaplerotic nature of the pyruvate carboxylase reaction and the phosphoenolpyruvate carboxylase reaction.

Which of the following is a reactant in the net reaction of the citrate cycle?

Explain the effect a high concentration of NADH has on the citrate cycle.

In two turns of the citrate cycle, how many electrons are transferred from the citrate cycle intermediates to NAD+ and FAD?

Which citrate cycle intermediate is siphoned off the citrate cycle during starvation?

You exercise vigorously for 30 minutes. Which chemical compounds would you expect to be elevated that would affect the regulation of pyruvate dehydrogenase? State the substances and explain how they would affect the regulation.

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

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.

Which reaction in the citrate cycle produces NADH?

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

Explain what redox reaction Δ\DeltaΔ E °\degree° ' values mean regarding spontaneity. How does the spontaneity affect the arrangement of multiple redox reactions in a linked metabolic pathway?

Which anaplerotic reactions do plants, yeast, and bacteria use to generate oxaloacetate?

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

Arsenite affects the lipoamide coenzymes of the pyruvate dehydrogenase reaction by

How would a high NADH to NAD+ ratio be expected to affect the pyruvate dehydrogenase reaction?

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

The primary function of NAD⁺in the citrate cycle is that it

The reaction catalyzed by is likely to be reversible under cellular conditions according to the $\Delta$ G $\degree$ ^' .

In two turns of the citrate cycle, how many electrons are transferred from the citrate cycle intermediates to NAD⁺and FAD?

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

Explain what redox reaction $\Delta$ E $\degree$ ^' values mean regarding spontaneity. How does the spontaneity affect the arrangement of multiple redox reactions in a linked metabolic pathway?

How would a high NADH to NAD⁺ratio be expected to affect the pyruvate dehydrogenase reaction?