Question 1

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

Question 2

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

Question 3

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. 
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.

Question 4

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. 
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.

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+ 
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+

Question 6

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 dehydrogenase 
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 dehydrogenase

Question 7

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. 
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.

Question 8

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 true 
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 true

Question 9

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. 
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.

Question 10

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-CoA 
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-CoA

Question 11

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. 
A)  pyruvate kinase. 
B)  glyceraldehyde-3-phosphate dehydrogenase. 
C)  isocitrate dehydrogenase. 
D)  pyruvate dehydrogenase. 
E)  lactate dehydrogenase.

Question 12

____ 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 true 
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 true

Question 13

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 true 
A)  β,β; electrophilic; trans 
B)  α,β; electrophilic; cis 
C)  α,β; stereospecific; trans 
D)  β,γ; stereospecific; cis 
E)  none are true

Question 14

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. 
A)  malate dehydrogenase. 
B)  citrate synthase. 
C)  isocitrate dehydrogenase. 
D)  succinyl-CoA synthetase. 
E)  nucleotide triphosphate kinase.

Question 15

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

Question 16

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

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:

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.

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

All are characteristics of succinyl-CoA synthetase EXCEPT:

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

Which enzymes of the TCA cycle catalyze oxidative decarboxylation reactions?

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

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

All are true for aconitase EXCEPT:

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

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

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

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

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

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

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

The Facts of Life: Chemistry Is the Logic of Biological Phenomena

Water: the Medium of Life

Thermodynamics of Biological Systems

Amino Acids and the Peptide Bond

Proteins: Their Primary Structure and Biological Functions

Proteins: Secondary, Tertiary, and Quaternary Structure

Carbohydrates and the Glycoconjugates of Cell Surfaces

Lipids

Membranes and Membrane Transport

Nucleotides and Nucleic Acids

Structure of Nucleic Acids

Recombinant Dna, Cloning, Chimeric Genes, and Synthetic Biology

Enzymeskinetics and Specificity

Mechanisms of Enzyme Action

Enzyme Regulation

Molecular Motors

Metabolism: an Overview

Glycolysis

Electron Transport and Oxidative Phosphorylation

Photosynthesis

Gluconeogenesis, Glycogen Metabolism, and the Pentose Phosphate Pathway

Fatty Acid Catabolism

Lipid Biosynthesis

Nitrogen Acquisition and Amino Acid Metabolism

Synthesis and Degradation of Nucleotides

Metabolic Integration and Organ Specialization

Dna Metabolism: Replication, Recombination, and Repair

Transcription and the Regulation of Gene Expression

Protein Synthesis

Completing the Protein Life Cycle: Folding, Processing, and Degradation

The Reception and Transmission of Extracellular Information

Filters

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

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

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

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

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