Question 1

Which molecule in the net reaction of the citrate cycle contributes to the inhibition of pyruvate dehydrogenase?

Accepted Answer

A)  FAD 
B)  H2O 
C)  H+ 
D)  NADH 
A)  FAD 
B)  H2O 
C)  H+ 
D)  NADH

Question 2

How would an increase in Ca2+ 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 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 inhibition of 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.

Question 3

A patient seeks medical attention for ulcerous skin lesions.The patient is diagnosed with

Accepted Answer

A)  arsenic exposure. 
B)  a deficiency in vitamin B3. 
C)  beriberi. 
D)  cheilosis. 
A)  arsenic exposure. 
B)  a deficiency in vitamin B3. 
C)  beriberi. 
D)  cheilosis.

Question 4

The primary function of the citrate cycle is to oxidize

Accepted Answer

A)  glucose. 
B)  pyruvate. 
C)  acetyl-CoA. 
D)  citrate. 
A)  glucose. 
B)  pyruvate. 
C)  acetyl-CoA. 
D)  citrate.

Question 5

How many ATP are produced from two turns of the citrate cycle?

Accepted Answer

A)  9 
B)  10 
C)  18 
D)  20 
A)  9 
B)  10 
C)  18 
D)  20

Question 6

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 7

Which enzyme regulates the flux of acetyl-CoA through the citrate cycle?

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 8

Use the figure below to answer the following questions.   A.The electrochemical cell shown here is measuring the reduction potential of Fe2+/Fe3+ using a reference hydrogen half reaction.Write each half reaction on the figure and show the flow of electrons.
B.Do these oxidants have a higher or lower affinity for electrons compared with H+? Explain how you know this using information from the experiment.

Accepted Answer

A.The reference hydrogen half reaction s

Question 9

Which molecules function as electron acceptors in the citrate cycle?

Accepted Answer

A)  NAD+, FAD 
B)  NADH, FADH2 
C)  GDP, ADP 
D)  GTP, ATP 
A)  NAD+, FAD 
B)  NADH, FADH2 
C)  GDP, ADP 
D)  GTP, ATP

Question 10

Compare the two ways the pyruvate dehydrogenase reaction is controlled by the cell.

Accepted Answer

Pyruvate dehydrogenase is regulated by a

Question 11

In linked metabolic pathways,the oxidants in subsequent reactions must

Accepted Answer

A)  result in negative  
Values at each reaction step. 
B)  result in positive  
Values at each reaction step. 
C)  have progressively lower standard reduction potentials. 
D)  have progressively higher standard reduction potentials. 
A)  result in negative  
Values at each reaction step. 
B)  result in positive  
Values at each reaction step. 
C)  have progressively lower standard reduction potentials. 
D)  have progressively higher standard reduction potentials.

Question 12

Which two enzymes in the citrate cycle are affected by arsenic poisoning?

Accepted Answer

A)  pyruvate dehydrogenase and succinate dehydrogenase 
B)  pyruvate dehydrogenase and  -ketoglutarate dehydrogenase 
C)  malate dehydrogenase and succinate dehydrogenase 
D)  malate dehydrogenase and  -ketoglutarate dehydrogenase 
A)  pyruvate dehydrogenase and succinate dehydrogenase 
B)  pyruvate dehydrogenase and  -ketoglutarate dehydrogenase 
C)  malate dehydrogenase and succinate dehydrogenase 
D)  malate dehydrogenase and  -ketoglutarate dehydrogenase

Question 13

Predict the fate of succinyl-CoA in the cell when it is not 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 14

Which citrate cycle intermediate is also used in gluconeogenesis?

Accepted Answer

A)  oxaloacetate 
B)    -ketoglutarate 
C)  fumarate 
D)  succinate 
A)  oxaloacetate 
B)    -ketoglutarate 
C)  fumarate 
D)  succinate

Question 15

Explain what redox reaction   
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 @#IMG-DLM&_TB6697_11

Question 16

The poison compound 1080 converts fluoroacetate to fluorocitrate.Which enzyme in the citrate cycle is inhibited by this poison?

Accepted Answer

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

Question 17

Which vitamin is the precursor to the coenzyme that functions as a reductant in the pyruvate dehydrogenase complex in the final step of the reaction?

Accepted Answer

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

Question 18

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 19

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 20

Which enzyme in the citrate cycle produces NADH?

Accepted Answer

A)  aconitase 
B)  citrate synthase 
C)  isocitrate dehydrogenase 
D)  fumarase 
A)  aconitase 
B)  citrate synthase 
C)  isocitrate dehydrogenase 
D)  fumarase

Exam 10: The Citrate Cycle

Which molecule in the net reaction of the citrate cycle contributes to the inhibition of pyruvate dehydrogenase?

How would an increase in Ca2+ be expected to affect the pyruvate dehydrogenase reaction?

A patient seeks medical attention for ulcerous skin lesions.The patient is diagnosed with

The primary function of the citrate cycle is to oxidize

How many ATP are produced from two turns of the citrate cycle?

Arsenite affects the lipoamide coenzymes of the pyruvate dehydrogenase reaction by

Which enzyme regulates the flux of acetyl-CoA through the citrate cycle?

Which molecules function as electron acceptors in the citrate cycle?

Compare the two ways the pyruvate dehydrogenase reaction is controlled by the cell.

In linked metabolic pathways,the oxidants in subsequent reactions must

Which two enzymes in the citrate cycle are affected by arsenic poisoning?

Predict the fate of succinyl-CoA in the cell when it is not in the citrate cycle.

Which citrate cycle intermediate is also used in gluconeogenesis?

Explain what redox reaction values mean regarding spontaneity.How does the spontaneity affect the arrangement of multiple redox reactions in a linked metabolic pathway?

The poison compound 1080 converts fluoroacetate to fluorocitrate.Which enzyme in the citrate cycle is inhibited by this poison?

Which vitamin is the precursor to the coenzyme that functions as a reductant in the pyruvate dehydrogenase complex in the final step of the reaction?

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.

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

Which enzyme in the citrate cycle produces NADH?

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

How would an increase in Ca²⁺ be expected to affect the pyruvate dehydrogenase reaction?