Question 1

During the oxidation of isocitrate, the intermediate that is decarboxylated to form $\alpha$-ketoglutarate is _____.

Accepted Answer

A)  oxalosuccinate 
B)  succinyl-phosphate 
C)  cis-aconitate 
D)  carboxybiotin 
E)  hydroxyethyl-TPP 
A)  oxalosuccinate 
B)  succinyl-phosphate 
C)  cis-aconitate 
D)  carboxybiotin 
E)  hydroxyethyl-TPP A

Question 2

Which of the following explains the proper binding of the two substrates for citrate synthase?

Accepted Answer

A)  the binding is random 
B)  acetyl-CoA binds, then oxaloacetate 
C)  oxaloacetate binds, then acetyl-CoA 
D)  oxaloacetate binds to one subunit, acetyl-CoA binds to the other 
E)  in one subunit, acetyl-CoA binds, then oxaloacetate; on the other subunit, this is reversed 
A)  the binding is random 
B)  acetyl-CoA binds, then oxaloacetate 
C)  oxaloacetate binds, then acetyl-CoA 
D)  oxaloacetate binds to one subunit, acetyl-CoA binds to the other 
E)  in one subunit, acetyl-CoA binds, then oxaloacetate; on the other subunit, this is reversed C

Question 3

What citric acid cycle intermediate is effectively used as a mechanism for the transport of acetyl-CoA from the mitochondria to the cytosol?

Accepted Answer

A)  citrate 
B)  isocitrate 
C)  fumarate 
D)  malate 
E)  oxaloacetate 
A)  citrate 
B)  isocitrate 
C)  fumarate 
D)  malate 
E)  oxaloacetate A

Question 4

Which of the following is observed in the mechanism of citrate synthase?

Accepted Answer

A)  a histidine residue acts as a base, deprotonating oxaloacetate 
B)  an aspartic acid residue acts as a base, deprotonating oxaloacetate 
C)  a histidine residue hydrogen bonds with the carbonyl oxygen of oxaloacetate to enable a nucleophilic attack 
D)  removal of the CoA is accomplished by transfer to a serine residue, then hydrolysis 
E)  all of the above 
A)  a histidine residue acts as a base, deprotonating oxaloacetate 
B)  an aspartic acid residue acts as a base, deprotonating oxaloacetate 
C)  a histidine residue hydrogen bonds with the carbonyl oxygen of oxaloacetate to enable a nucleophilic attack 
D)  removal of the CoA is accomplished by transfer to a serine residue, then hydrolysis 
E)  all of the above

Question 5

Which of the following terms indicates that the citric acid cycle is both catabolic and anabolic in nature?

Accepted Answer

A)  cataplerotic 
B)  amphipathic 
C)  anaplerotic 
D)  diabolic 
E)  amphibolic 
A)  cataplerotic 
B)  amphipathic 
C)  anaplerotic 
D)  diabolic 
E)  amphibolic

Question 6

Why can germinating plant seeds convert acetyl-CoA from fatty acids into carbohydrates, while animals are incapable of converting fatty acids into glucose?

Accepted Answer

A)  animals have glycogen and don't need to make glucose from fatty acids 
B)  plants, not animals, use the glyoxylate cycle to convert acetyl CoA to oxaloacetate 
C)  plant seeds use photosynthesis to make sugar 
D)  animals use the citric acid cycle exclusively for energy production, plants only use glycolysis for energy 
E)  none of the above 
A)  animals have glycogen and don't need to make glucose from fatty acids 
B)  plants, not animals, use the glyoxylate cycle to convert acetyl CoA to oxaloacetate 
C)  plant seeds use photosynthesis to make sugar 
D)  animals use the citric acid cycle exclusively for energy production, plants only use glycolysis for energy 
E)  none of the above

Question 7

Which of the following can be converted into glucose using parts of the citric acid cycle?

Accepted Answer

A)  malate 
B)  isocitrate 
C)  glutamic acid 
D)  succinate 
E)  all of the above 
A)  malate 
B)  isocitrate 
C)  glutamic acid 
D)  succinate 
E)  all of the above

Question 8

If acetyl-CoA labeled on the methyl carbon were used as the substrate for the citric acid cycle, where would the labeled carbon appear in oxaloacetate produced from one round of the cycle?

Accepted Answer

A)  C1 
B)  C4 
C)  C1 or C2 
D)  C1 or C4 
E)  C2 or C3 
A)  C1 
B)  C4 
C)  C1 or C2 
D)  C1 or C4 
E)  C2 or C3

Question 9

Which of the following enzymes allows for a net increase of citric acid cycle metabolites without expending any energy in the form of ATP or its equivalents?

Accepted Answer

A)  alanine aminotransferase 
B)  pyruvate dehydrogenase 
C)  pyruvate carboxylase 
D)  citrate lyase 
E)  none of the above 
A)  alanine aminotransferase 
B)  pyruvate dehydrogenase 
C)  pyruvate carboxylase 
D)  citrate lyase 
E)  none of the above

Question 10

Which of the following describes the isomerization of citrate to isocitrate?

Accepted Answer

A)  a major regulatory step for the citric acid cycle 
B)  an oxidation reaction 
C)  the only unnecessary step of the citric acid cycle 
D)  protects cells from the toxic effects of arsenite ion 
E)  converts a tertiary alcohol, which cannot easily be oxidized, to a secondary alcohol that can be oxidized 
A)  a major regulatory step for the citric acid cycle 
B)  an oxidation reaction 
C)  the only unnecessary step of the citric acid cycle 
D)  protects cells from the toxic effects of arsenite ion 
E)  converts a tertiary alcohol, which cannot easily be oxidized, to a secondary alcohol that can be oxidized

Question 11

Which of the following is an enzyme-associated intermediate that is similar in energy to 1,3-bisphosphoglycerate?

Accepted Answer

A)  phosphohistidine 
B)  succinyl phosphate 
C)  oxalosuccinate 
D)  carboxybiotin 
E)  hydroxyethyl-TPP 
A)  phosphohistidine 
B)  succinyl phosphate 
C)  oxalosuccinate 
D)  carboxybiotin 
E)  hydroxyethyl-TPP

Question 12

What amino acid is covalently linked to lipoic acid in E2?

Accepted Answer

A)  Lys 
B)  Ser 
C)  His 
D)  Gln 
E)  Thr 
A)  Lys 
B)  Ser 
C)  His 
D)  Gln 
E)  Thr

Question 13

If all reduced electron carriers are reoxidized to run oxidative phosphorylation, how many ATP can be generated from the oxidation of one acetyl-CoA?

Accepted Answer

A)  6 
B)  10 
C)  15 
D)  20 
E)  32 
A)  6 
B)  10 
C)  15 
D)  20 
E)  32

Question 14

When acetyl-CoA and NADPH are needed for lipid synthesis, which of the following reactions is used to produce NADPH in the cytosol?

Accepted Answer

A)  reduction of oxaloacetate to malate 
B)  oxidation of malate to pyruvate 
C)  reduction of fumarate to succinate 
D)  oxidation of malate to oxaloacetate 
E)  oxidation of isocitrate to $\beta$-ketoglutarate 
A)  reduction of oxaloacetate to malate 
B)  oxidation of malate to pyruvate 
C)  reduction of fumarate to succinate 
D)  oxidation of malate to oxaloacetate 
E)  oxidation of isocitrate to $\beta$-ketoglutarate

Question 15

If acetyl-CoA labeled with 14C, as shown in the figure, were used as the substrate for the citric acid cycle, which of the following intermediates would be produced during the first round of the cycle?

Accepted Answer

A) 
  
B) 
  
C) 
  
D) 
  
E) 
  
A) 
  
B) 
  
C) 
  
D) 
  
E)

Question 16

What makes the reaction catalyzed by citrate synthase highly exergonic?

Accepted Answer

A)  hydrolysis of ATP 
B)  hydrolysis of GTP 
C)  decarboxylation reaction 
D)  conversion from keto to enol tautomer 
E)  hydrolysis of thioester 
A)  hydrolysis of ATP 
B)  hydrolysis of GTP 
C)  decarboxylation reaction 
D)  conversion from keto to enol tautomer 
E)  hydrolysis of thioester

Question 17

The mechanism of malate synthase that catalyzes the conversion of glyoxylate and acetyl-CoA to malate would be most similar to which citric acid cycle enzyme?

Accepted Answer

A)  fumarase 
B)  aconitase 
C)  citrate synthase 
D)  isocitrate dehydrogenase 
E)  succinyl-CoA synthetase 
A)  fumarase 
B)  aconitase 
C)  citrate synthase 
D)  isocitrate dehydrogenase 
E)  succinyl-CoA synthetase

During the oxidation of isocitrate, the intermediate that is decarboxylated to form $\alpha$ -ketoglutarate is _____.

Which of the following explains the proper binding of the two substrates for citrate synthase?

What citric acid cycle intermediate is effectively used as a mechanism for the transport of acetyl-CoA from the mitochondria to the cytosol?

Which of the following is observed in the mechanism of citrate synthase?

Which of the following terms indicates that the citric acid cycle is both catabolic and anabolic in nature?

Why can germinating plant seeds convert acetyl-CoA from fatty acids into carbohydrates, while animals are incapable of converting fatty acids into glucose?

Which of the following can be converted into glucose using parts of the citric acid cycle?

If acetyl-CoA labeled on the methyl carbon were used as the substrate for the citric acid cycle, where would the labeled carbon appear in oxaloacetate produced from one round of the cycle?

Which of the following enzymes allows for a net increase of citric acid cycle metabolites without expending any energy in the form of ATP or its equivalents?

Which of the following describes the isomerization of citrate to isocitrate?

Which of the following is an enzyme-associated intermediate that is similar in energy to 1,3-bisphosphoglycerate?

What amino acid is covalently linked to lipoic acid in E2?

If all reduced electron carriers are reoxidized to run oxidative phosphorylation, how many ATP can be generated from the oxidation of one acetyl-CoA?

When acetyl-CoA and NADPH are needed for lipid synthesis, which of the following reactions is used to produce NADPH in the cytosol?

If acetyl-CoA labeled with ¹⁴C, as shown in the figure, were used as the substrate for the citric acid cycle, which of the following intermediates would be produced during the first round of the cycle?

What makes the reaction catalyzed by citrate synthase highly exergonic?

The mechanism of malate synthase that catalyzes the conversion of glyoxylate and acetyl-CoA to malate would be most similar to which citric acid cycle enzyme?

The Chemical Basis of Life

Aqueous Chemistry

Nucleic Acid Structure and Function

Protein Structure

Protein Function

How Enzymes Work

Enzyme Kinetics and Inhibition

Lipids and Membranes

Membrane Transport

Signaling

Carbohydrates

Metabolism and Bioenergetics

Glucose Metabolism

Oxidative Phosphorylation

Photosynthesis

Lipid Metabolism

Nitrogen Metabolism

Regulation of Mammalian Fuel Metabolism

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Transcription and RNA

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Exam 14: The Citric Acid Cycle

During the oxidation of isocitrate, the intermediate that is decarboxylated to form α\alphaα -ketoglutarate is _____.

Which of the following explains the proper binding of the two substrates for citrate synthase?

What citric acid cycle intermediate is effectively used as a mechanism for the transport of acetyl-CoA from the mitochondria to the cytosol?

Which of the following is observed in the mechanism of citrate synthase?

Which of the following terms indicates that the citric acid cycle is both catabolic and anabolic in nature?

Why can germinating plant seeds convert acetyl-CoA from fatty acids into carbohydrates, while animals are incapable of converting fatty acids into glucose?

Which of the following can be converted into glucose using parts of the citric acid cycle?

If acetyl-CoA labeled on the methyl carbon were used as the substrate for the citric acid cycle, where would the labeled carbon appear in oxaloacetate produced from one round of the cycle?

Which of the following enzymes allows for a net increase of citric acid cycle metabolites without expending any energy in the form of ATP or its equivalents?

Which of the following describes the isomerization of citrate to isocitrate?

Which of the following is an enzyme-associated intermediate that is similar in energy to 1,3-bisphosphoglycerate?

What amino acid is covalently linked to lipoic acid in E2?

If all reduced electron carriers are reoxidized to run oxidative phosphorylation, how many ATP can be generated from the oxidation of one acetyl-CoA?

When acetyl-CoA and NADPH are needed for lipid synthesis, which of the following reactions is used to produce NADPH in the cytosol?

If acetyl-CoA labeled with 14C, as shown in the figure, were used as the substrate for the citric acid cycle, which of the following intermediates would be produced during the first round of the cycle?

What makes the reaction catalyzed by citrate synthase highly exergonic?

The mechanism of malate synthase that catalyzes the conversion of glyoxylate and acetyl-CoA to malate would be most similar to which citric acid cycle enzyme?

The Chemical Basis of Life

Aqueous Chemistry

Nucleic Acid Structure and Function

Protein Structure

Protein Function

How Enzymes Work

Enzyme Kinetics and Inhibition

Lipids and Membranes

Membrane Transport

Signaling

Carbohydrates

Metabolism and Bioenergetics

Glucose Metabolism

Oxidative Phosphorylation

Photosynthesis

Lipid Metabolism

Nitrogen Metabolism

Regulation of Mammalian Fuel Metabolism

DNA Replication and Repair

Transcription and RNA

Protein Synthesis

Filters

During the oxidation of isocitrate, the intermediate that is decarboxylated to form $\alpha$ -ketoglutarate is _____.

If acetyl-CoA labeled with ¹⁴C, as shown in the figure, were used as the substrate for the citric acid cycle, which of the following intermediates would be produced during the first round of the cycle?