Question 1

____ catalyzes citrate isomerization to isocitrate by abstracting ____ from citrate to yield the enzyme-bound intermediate ____, followed by ____ to produce isocitrate.

Accepted Answer

A)   Citrate isomerase; CO2; trans-aconitate; carboxylation
B)   Citrate isomerase; water; trans-aconitate; rehydration
C)   Aconitase; water; cis-aconitate; rehydration
D)   Aconitase; CO2; cis-aconitate; carboxylation
E)   None are trueF) B) and C)
G) None of the above

Question 2

All are correct statements about the reaction catalyzed by citrate synthase EXCEPT:

Accepted Answer

A)   Citrate synthase is allosterically activated by ATP.
B)   The complete chemical equation is: Oxaloacetate + acetyl-CoA + H2O → citrate + CoA
C)   Citryl-CoA is formed as an intermediate.
D)   The mechanism involves attack of the carbanion of acetyl-CoA on the carbonyl carbon of oxaloacetate.
E)   The enzyme uses general base catalysis to generate the reactive species.F) B) and D)
G) D) and E)

Question 3

Fumarase catalyzes a reaction for which each of the following is true EXCEPT:

Accepted Answer

A)   fumarate is hydrated
B)   the reaction is stereospecific for a trans product
C)   the reaction involved is similar to that carried out by aconitase
D)   L-malate is the produced
E)   all are trueF) B) and E)
G) B) and C)

Question 4

Inhibition of the citric acid cycle at isocitrate dehydrogenase increases the levels of citrate and isocitrate that may increase the production of:

Accepted Answer

A)   amino acids.
B)   pyruvate and oxaloacetate.
C)   glyoxylate and cytosolic acetyl-CoA.
D)   succinate and fumarate.
E)   lactate and alanine.F) A) and C)
G) A) and E)

Question 5

Mammalian pyruvate dehydrogenase is regulated by phosphorylation using the enzyme ____ which is allosterically activated by high levels of ____ and ____.

Accepted Answer

A)   pyruvate kinase; ATP; acetyl-CoA
B)   pyruvate kinase; NADH; NADPH
C)   pyruvate carboxylase; acetyl-CoA; ATP
D)   pyruvate dehydrogenase kinase; NADH; acetyl-CoA
E)   pyruvate dehydrogenase kinase; ADP; NAD+F) None of the above
G) All of the above

Question 6

The only reaction of the citric acid cycle that provides substrate-level phosphorylation is catalyzed by:

Accepted Answer

A)   malate dehydrogenase.
B)   citrate synthase.
C)   isocitrate dehydrogenase.
D)   succinyl-CoA synthetase.
E)   nucleotide triphosphate kinase.F) All of the above
G) B) and C)

Question 7

In the TCA cycle, ____ oxidation(s)  use(s)  NAD+ as the oxidizing agent while ____ oxidation(s)  use(s)  FAD as the oxidizing agent.

Accepted Answer

A)   0; 4
B)   1; 3
C)   2; 2
D)   3; 1
E)   4; 0F) A) and B)
G) B) and E)

Question 8

When acetyl-CoA levels exceed the ____ supply, allosteric activation of ____ by ____ raises the oxaloacetate (OAA)  levels for condensation with acetyl-CoA to form ____.

Accepted Answer

A)   citrate; citrate synthase; acetyl-CoA; citrate
B)   malate; malate dehydrogenase; ATP; citrate
C)   OAA; citrate synthase; acetyl-CoA; isocitrate
D)   OAA; pyruvate carboxylase; acetyl-CoA; citrate
E)   Acetyl-CoA; pyruvate carboxylase; citrate; acetyl-CoAF) C) and D)
G) B) and D)

Question 9

The correct sequence of electron transport in the succinate dehydrogenase reaction mechanism is:
A.Coenzyme Q (UQ) .
B.[FAD].
C.iron-sulfur clusters.
D.electron transport chain.

Accepted Answer

A)   A, B, C, D
B)   B, C, D, A
C)   B, C, A, D
D)   C, B, D, A
E)   C, D, A, BF) C) and D)
G) None of the above

Question 10

Which enzymes of the TCA cycle catalyze oxidative decarboxylation reactions?

Accepted Answer

A)   malate dehydrogenase and citrate synthase
B)   fumarase and succinate dehydrogenase
C)   α-ketoglutarate dehydrogenase and succinate dehydrogenase
D)   isocitrate dehydrogenase and α-ketoglutarate dehydrogenase
E)   aconitase and succinate dehydrogenaseF) A) and E)
G) B) and C)

Question 11

Which of the following represents a reaction that could be used to refill the CAC?:

Accepted Answer

A)   OAA → PEP
B)   citrate → OAA + acetyl-CoA
C)   Asp → α-ketoglutarate
D)   pyruvate → OAA
E)   none of the aboveF) A) and D)
G) A) and E)

Question 12

All are characteristics of succinyl-CoA synthetase EXCEPT:

Accepted Answer

A)   succinyl-CoA can be used to drive phosphorylation of GDP or ADP.
B)   the enzyme is named for the reverse reaction.
C)   it provides an example of substrate-level phosphorylation.
D)   succinyl-phosphate is an intermediate in the reaction catalyzed by succinyl-CoA synthetase.
E)   all of the above are true.F) C) and D)
G) A) and B)

Question 13

The anaplerotic reactions associated with the TCA cycle are a result of the:

Accepted Answer

A)   use of many of the TCA cycle intermediates in biosynthesis.
B)   oxidative nature of the TCA cycle.
C)   decarboxylation reactions.
D)   production of GTP and reduced coenzymes.
E)   irreversible nature of some of the TCA cycle reactions.F) A) and D)
G) B) and D)

Question 14

All are true for aconitase EXCEPT:

Accepted Answer

A)   iron atom acts as a Lewis acid.
B)   equilibrium favors citrate.
C)   contains an iron-sulfur cluster.
D)   one Fe3+ coordinates with C-3 carbonyl and hydroxyl group of citrate.
E)   all are true.F) D) and E)
G) All of the above

Question 15

The succinate dehydrogenase catalyzed reaction involves dehydrogenation ____ to a carbonyl group and is ____ to yield a ____ double bond.

Accepted Answer

A)   β,β; electrophilic; trans
B)   α,β; electrophilic; cis
C)   α,β; stereospecific; trans
D)   β,γ; stereospecific; cis
E)   none are trueF) None of the above
G) C) and E)

Question 16

α-Ketoglutarate dehydrogenase is a multi-enzyme complex analogous to:

Accepted Answer

A)   pyruvate kinase.
B)   glyceraldehyde-3-phosphate dehydrogenase.
C)   isocitrate dehydrogenase.
D)   pyruvate dehydrogenase.
E)   lactate dehydrogenase.F) A) and B)
G) None of the above

Exam 19: The Tricarboxylic Acid Cycle

Inhibition of the citric acid cycle at isocitrate dehydrogenase increases the levels of citrate and isocitrate that may increase the production of:

Correct Answer
verified

Which of the following represents a reaction that could be used to refill the CAC?:

Correct Answer
verified

α-Ketoglutarate dehydrogenase is a multi-enzyme complex analogous to:

Correct Answer
verified

Mammalian pyruvate dehydrogenase is regulated by phosphorylation using the enzyme which is allosterically activated by high levels of and .

Correct Answer
verified

The succinate dehydrogenase catalyzed reaction involves dehydrogenation to a carbonyl group and is to yield a double bond.

Correct Answer
verified

The anaplerotic reactions associated with the TCA cycle are a result of the:

Correct Answer
verified

When acetyl-CoA levels exceed the supply, allosteric activation of by raises the oxaloacetate (OAA) levels for condensation with acetyl-CoA to form .

Correct Answer
verified

catalyzes citrate isomerization to isocitrate by abstracting from citrate to yield the enzyme-bound intermediate , followed by to produce isocitrate.

Correct Answer
verified

The correct sequence of electron transport in the succinate dehydrogenase reaction mechanism is: A.Coenzyme Q (UQ) . B.[FAD]. C.iron-sulfur clusters. D.electron transport chain.

Correct Answer
verified

All are true for aconitase EXCEPT:

Correct Answer
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In the TCA cycle, oxidation(s) use(s) NAD⁺ as the oxidizing agent while oxidation(s) use(s) FAD as the oxidizing agent.

Correct Answer
verified

Fumarase catalyzes a reaction for which each of the following is true EXCEPT:

Correct Answer
verified

The only reaction of the citric acid cycle that provides substrate-level phosphorylation is catalyzed by:

Correct Answer
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All are correct statements about the reaction catalyzed by citrate synthase EXCEPT:

Correct Answer
verified

All are characteristics of succinyl-CoA synthetase EXCEPT:

Correct Answer
verified

Which enzymes of the TCA cycle catalyze oxidative decarboxylation reactions?

Correct Answer
verified

Exam 19: The Tricarboxylic Acid Cycle

Inhibition of the citric acid cycle at isocitrate dehydrogenase increases the levels of citrate and isocitrate that may increase the production of:

Correct AnswerverifiedShow Answer

Which of the following represents a reaction that could be used to refill the CAC?:

Correct AnswerverifiedShow Answer

α-Ketoglutarate dehydrogenase is a multi-enzyme complex analogous to:

Correct AnswerverifiedShow Answer

Mammalian pyruvate dehydrogenase is regulated by phosphorylation using the enzyme ____ which is allosterically activated by high levels of ____ and ____.

Correct AnswerverifiedShow Answer

The succinate dehydrogenase catalyzed reaction involves dehydrogenation ____ to a carbonyl group and is ____ to yield a ____ double bond.

Correct AnswerverifiedShow Answer

The anaplerotic reactions associated with the TCA cycle are a result of the:

Correct AnswerverifiedShow Answer

When acetyl-CoA levels exceed the ____ supply, allosteric activation of ____ by ____ raises the oxaloacetate (OAA) levels for condensation with acetyl-CoA to form ____.

Correct AnswerverifiedShow Answer

____ catalyzes citrate isomerization to isocitrate by abstracting ____ from citrate to yield the enzyme-bound intermediate ____, followed by ____ to produce isocitrate.

Correct AnswerverifiedShow Answer

The correct sequence of electron transport in the succinate dehydrogenase reaction mechanism is: A.Coenzyme Q (UQ) . B.[FAD]. C.iron-sulfur clusters. D.electron transport chain.

Correct AnswerverifiedShow Answer

All are true for aconitase EXCEPT:

Correct AnswerverifiedShow Answer

In the TCA cycle, ____ oxidation(s) use(s) NAD+ as the oxidizing agent while ____ oxidation(s) use(s) FAD as the oxidizing agent.

Correct AnswerverifiedShow Answer

Fumarase catalyzes a reaction for which each of the following is true EXCEPT:

Correct AnswerverifiedShow Answer

The only reaction of the citric acid cycle that provides substrate-level phosphorylation is catalyzed by:

Correct AnswerverifiedShow Answer

All are correct statements about the reaction catalyzed by citrate synthase EXCEPT:

Correct AnswerverifiedShow Answer

All are characteristics of succinyl-CoA synthetase EXCEPT:

Correct AnswerverifiedShow Answer

Which enzymes of the TCA cycle catalyze oxidative decarboxylation reactions?

Correct AnswerverifiedShow Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Mammalian pyruvate dehydrogenase is regulated by phosphorylation using the enzyme which is allosterically activated by high levels of and .

Correct Answer
verified

The succinate dehydrogenase catalyzed reaction involves dehydrogenation to a carbonyl group and is to yield a double bond.

Correct Answer
verified

Correct Answer
verified

When acetyl-CoA levels exceed the supply, allosteric activation of by raises the oxaloacetate (OAA) levels for condensation with acetyl-CoA to form .

Correct Answer
verified

catalyzes citrate isomerization to isocitrate by abstracting from citrate to yield the enzyme-bound intermediate , followed by to produce isocitrate.

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

In the TCA cycle, oxidation(s) use(s) NAD⁺ as the oxidizing agent while oxidation(s) use(s) FAD as the oxidizing agent.

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
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Correct Answer
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Correct Answer
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