Question 1

In the TCA cycle, carbon enters the cycle as ____ and exits as ____ with metabolic energy captured as ____, ____ and ____.

Accepted Answer

A)  malonate; water; NADH; ATP; NADPH 
B)  acetyl-CoA; CO2; NADH; ATP; NADPH 
C)  succinyl-CoA; CO2; ATP; NADH; NADPH 
D)  acetyl-CoA; CO2; ATP; NADH; [FADH2] 
E)  malonyl-CoA; water; NADH; [FADH2]; ATP 
A)  malonate; water; NADH; ATP; NADPH 
B)  acetyl-CoA; CO2; NADH; ATP; NADPH 
C)  succinyl-CoA; CO2; ATP; NADH; NADPH 
D)  acetyl-CoA; CO2; ATP; NADH; [FADH2] 
E)  malonyl-CoA; water; NADH; [FADH2]; ATP

Question 2

Isocitrate dehydrogenase has all of the characteristics EXCEPT:

Accepted Answer

A)  ADP raises the Km for isocitrate by a factor of 10. 
B)  virtually inactive in the absence of ADP. 
C)  sufficiently exergonic to pull the aconitase reaction forward. 
D)  allosterically inhibited by NADH and ATP. 
E)  an oxidative-decarboxylation reaction. 
A)  ADP raises the Km for isocitrate by a factor of 10. 
B)  virtually inactive in the absence of ADP. 
C)  sufficiently exergonic to pull the aconitase reaction forward. 
D)  allosterically inhibited by NADH and ATP. 
E)  an oxidative-decarboxylation reaction.

Question 3

Order the coenzymes according to their involvement in the pyruvate dehydrogenase complex.
A.NAD+
B.CoA-SH
C.TPP
D.Lipoate (lipoamide)
E.[FAD]

Accepted Answer

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

Question 4

Citrate synthase has a ____ ΔG°′ and is essentially ____ due to the ____ of the CoA thioester.

Accepted Answer

A)  large positive; reversible; oxidation 
B)  nearly zero; reversible; reduction 
C)  nearly zero; irreversible; reduction 
D)  large negative; irreversible; hydrolysis 
E)  large negative; reversible; hydrolysis 
A)  large positive; reversible; oxidation 
B)  nearly zero; reversible; reduction 
C)  nearly zero; irreversible; reduction 
D)  large negative; irreversible; hydrolysis 
E)  large negative; reversible; hydrolysis

Question 5

Allosteric inhibitors of isocitrate dehydrogenase include ____ and ____, whereas ____ acts as an allosteric activator, ____ the Km for isocitrate.

Accepted Answer

A)  ATP; NADH; ADP; lowering 
B)  ATP; ADP; AMP; lowering 
C)  NADH; NADPH; AMP; increasing 
D)  NADH; ATP; ADP; increasing 
E)  NADH; ATP; AMP; lowering 
A)  ATP; NADH; ADP; lowering 
B)  ATP; ADP; AMP; lowering 
C)  NADH; NADPH; AMP; increasing 
D)  NADH; ATP; ADP; increasing 
E)  NADH; ATP; AMP; lowering

Question 6

All are true for pyruvate carboxylase EXCEPT:

Accepted Answer

A)  an anaplerotic reaction. 
B)  in mitochondria of plants, but not animals. 
C)  is tetrameric. 
D)  contains covalently bound biotin. 
E)  absolute allosteric requirement for acetyl-CoA. 
A)  an anaplerotic reaction. 
B)  in mitochondria of plants, but not animals. 
C)  is tetrameric. 
D)  contains covalently bound biotin. 
E)  absolute allosteric requirement for acetyl-CoA.

Question 7

Discuss the metabolites that can be synthesized from citrate in the tricarboxylic acid cycle.​

Accepted Answer

Citrate can be exported from the mitocho

Question 8

It is crucial that regulation occur at pyruvate dehydrogenase because:

Accepted Answer

A)  pyruvate kinase is reversible. 
B)  lactate dehydrogenase is the only other enzyme to use pyruvate. 
C)  the product acetyl-CoA is committed to oxidation in the citric acid cycle or fatty acid biosynthesis. 
D)  alanine aminotransferase would use the pyruvate. 
E)  all of the above. 
A)  pyruvate kinase is reversible. 
B)  lactate dehydrogenase is the only other enzyme to use pyruvate. 
C)  the product acetyl-CoA is committed to oxidation in the citric acid cycle or fatty acid biosynthesis. 
D)  alanine aminotransferase would use the pyruvate. 
E)  all of the above.

Question 9

Discuss the regulation of tricarboxylic acid cycle enzymes by acetylation.​

Accepted Answer

Acetylation inhibits TCA enzyme activity

Question 10

The reaction CO2 + PEP + GDP   OAA + GTP is catalyzed by:

Accepted Answer

A)  PEP carboxylase. 
B)  PEP carboxykinase. 
C)  malic enzyme. 
D)  pyruvate carboxylase. 
E)  None are true. 
A)  PEP carboxylase. 
B)  PEP carboxykinase. 
C)  malic enzyme. 
D)  pyruvate carboxylase. 
E)  None are true.

Question 11

Characteristics of the oxidation of malate to oxaloacetate (OAA) include all EXCEPT:

Accepted Answer

A)  catalyzed by malate dehydrogenase. 
B)  uses NAD+ as an electron acceptor. 
C)  is very exergonic. 
D)  results in higher levels of malate than oxaloacetate. 
E)  is structurally and functionally similar to lactate dehydrogenase. 
A)  catalyzed by malate dehydrogenase. 
B)  uses NAD+ as an electron acceptor. 
C)  is very exergonic. 
D)  results in higher levels of malate than oxaloacetate. 
E)  is structurally and functionally similar to lactate dehydrogenase.

Question 12

The three reactions of the citric acid cycle with large negative ΔG values include:
A.citrate synthasE.
B.aconitasE.
C.isocitrate dehydrogenasE.
D.α-ketoglutarate dehydrogenas
E.E.succinyl-CoA synthetasE.
F.Succinyl-CoA dehydrogenasE.
G.FumarasE.
H.Malate dehydrogenase.

Accepted Answer

A)  A, B, C 
B)  A, C, D 
C)  C, E, F 
D)  B, C, E 
E)  A, C, H 
A)  A, B, C 
B)  A, C, D 
C)  C, E, F 
D)  B, C, E 
E)  A, C, H

Question 13

What is the function of thiamine pyrophosphate (TPP) in the reaction mechanism of the pyruvate dehydrogenase complex in the tricarboxylic acid (TCA) cycle?​

Accepted Answer

The cationic imine nitrogen of the thiaz

Question 14

Fluoroacetate is a potent inhibitor of the TCA cycle. Which step of the TCA cycle is inhibited as a result of fluoroacetate entering the TCA cycle?

Accepted Answer

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

Question 15

Which of the following coenzymes is NOT used by pyruvate dehydrogenase?

Accepted Answer

A)  NAD+ 
B)  FAD 
C)  thiamine pyrophosphate 
D)  tetrahydrofolate 
E)  lipoic acid 
A)  NAD+ 
B)  FAD 
C)  thiamine pyrophosphate 
D)  tetrahydrofolate 
E)  lipoic acid

Question 16

In eukaryotic cells, glycolysis occurs in the ____, and the TCA cycle reactions take place in ____.

Accepted Answer

A)  mitochondria; mitochondria 
B)  cytoplasm; mitochondria 
C)  cytoplasm; cytoplasm 
D)  mitochondria; ribosomes 
E)  cytoplasm; ribosomes 
A)  mitochondria; mitochondria 
B)  cytoplasm; mitochondria 
C)  cytoplasm; cytoplasm 
D)  mitochondria; ribosomes 
E)  cytoplasm; ribosomes

Question 17

All are principal allosteric regulatory "signals" controlling the TCA cycle activity EXCEPT:

Accepted Answer

A)  acetyl-CoA. 
B)  NADH. 
C)  NAD+. 
D)  ATP. 
E)  all are true. 
A)  acetyl-CoA. 
B)  NADH. 
C)  NAD+. 
D)  ATP. 
E)  all are true.

Question 18

Characteristics of succinate dehydrogenase include all EXCEPT:

Accepted Answer

A)  it is also known as succinate-Coenzyme Q reductase. 
B)  it has covalently bound FAD. 
C)  it is a membrane-bound enzyme. 
D)  it removes hydrogens from C-O bonds. 
E)  it carries out either 1-electron or 2-electron transfers to/from FAD. 
A)  it is also known as succinate-Coenzyme Q reductase. 
B)  it has covalently bound FAD. 
C)  it is a membrane-bound enzyme. 
D)  it removes hydrogens from C-O bonds. 
E)  it carries out either 1-electron or 2-electron transfers to/from FAD.

Question 19

The oxidation of malate to oxaloacetate is not thermodynamically favored under standard conditions. It occurs because:

Accepted Answer

A)  it involves substrate-level phosphorylation. 
B)  it is coupled with a strong reduction. 
C)  it is coupled with ATP hydrolysis. 
D)  oxaloacetate is used in the next reaction, which has a negative ΔG. 
E)  the previous reaction has a large negative ΔG. 
A)  it involves substrate-level phosphorylation. 
B)  it is coupled with a strong reduction. 
C)  it is coupled with ATP hydrolysis. 
D)  oxaloacetate is used in the next reaction, which has a negative ΔG. 
E)  the previous reaction has a large negative ΔG.

Question 20

Discuss the role of fumarase in the tricarboxylic acid cycle.​

Accepted Answer

Fumarate is hydrated in a stereospecific

Exam 19: The Tricarboxylic Acid Cycle

In the TCA cycle, carbon enters the cycle as ____ and exits as ____ with metabolic energy captured as ____, ____ and ____.

Isocitrate dehydrogenase has all of the characteristics EXCEPT:

Order the coenzymes according to their involvement in the pyruvate dehydrogenase complex. A.NAD+ B.CoA-SH C.TPP D.Lipoate (lipoamide) E.[FAD]

Citrate synthase has a ____ ΔG°′ and is essentially ____ due to the ____ of the CoA thioester.

Allosteric inhibitors of isocitrate dehydrogenase include ____ and ____, whereas ____ acts as an allosteric activator, ____ the Km for isocitrate.

All are true for pyruvate carboxylase EXCEPT:

Discuss the metabolites that can be synthesized from citrate in the tricarboxylic acid cycle.​

It is crucial that regulation occur at pyruvate dehydrogenase because:

Discuss the regulation of tricarboxylic acid cycle enzymes by acetylation.​

The reaction CO2 + PEP + GDP OAA + GTP is catalyzed by:

Characteristics of the oxidation of malate to oxaloacetate (OAA) include all EXCEPT:

The three reactions of the citric acid cycle with large negative ΔG values include: A.citrate synthasE. B.aconitasE. C.isocitrate dehydrogenasE. D.α-ketoglutarate dehydrogenas E.E.succinyl-CoA synthetasE. F.Succinyl-CoA dehydrogenasE. G.FumarasE. H.Malate dehydrogenase.

What is the function of thiamine pyrophosphate (TPP) in the reaction mechanism of the pyruvate dehydrogenase complex in the tricarboxylic acid (TCA) cycle?​

Fluoroacetate is a potent inhibitor of the TCA cycle. Which step of the TCA cycle is inhibited as a result of fluoroacetate entering the TCA cycle?

Which of the following coenzymes is NOT used by pyruvate dehydrogenase?

In eukaryotic cells, glycolysis occurs in the ____, and the TCA cycle reactions take place in ____.

All are principal allosteric regulatory "signals" controlling the TCA cycle activity EXCEPT:

Characteristics of succinate dehydrogenase include all EXCEPT:

The oxidation of malate to oxaloacetate is not thermodynamically favored under standard conditions. It occurs because:

Discuss the role of fumarase in the tricarboxylic acid cycle.​

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

In the TCA cycle, carbon enters the cycle as and exits as with metabolic energy captured as , and .

Order the coenzymes according to their involvement in the pyruvate dehydrogenase complex. A.NAD⁺ B.CoA-SH C.TPP D.Lipoate (lipoamide) E.[FAD]

Citrate synthase has a ΔG°′ and is essentially due to the of the CoA thioester.

Allosteric inhibitors of isocitrate dehydrogenase include and , whereas acts as an allosteric activator, the K_m for isocitrate.

Discuss the metabolites that can be synthesized from citrate in the tricarboxylic acid cycle.

Discuss the regulation of tricarboxylic acid cycle enzymes by acetylation.

The reaction CO₂ + PEP + GDP OAA + GTP is catalyzed by:

What is the function of thiamine pyrophosphate (TPP) in the reaction mechanism of the pyruvate dehydrogenase complex in the tricarboxylic acid (TCA) cycle?

In eukaryotic cells, glycolysis occurs in the , and the TCA cycle reactions take place in .

Discuss the role of fumarase in the tricarboxylic acid cycle.