Question 1

The isocitrate lyase catalyzed reaction cleaves isocitrate into:

Accepted Answer

A)  glyoxylate and fumarate. 
B)  succinate and acetyl-CoA. 
C)  malate and acetyl-CoA. 
D)  succinate and glyoxylate. 
E)  glyoxylate and acetyl-CoA. 
A)  glyoxylate and fumarate. 
B)  succinate and acetyl-CoA. 
C)  malate and acetyl-CoA. 
D)  succinate and glyoxylate. 
E)  glyoxylate and acetyl-CoA. D

Question 2

Which of the following is correctly paired with its inhibitor?

Accepted Answer

A)  pyruvate dehydrogenase: phosphorylation 
B)  isocitrate dehydrogenase: AMP 
C)  α-ketoglutarate dehydrogenase: NAD+ 
D)  citrate synthase: acetyl CoA 
E)  none of the above are correct 
A)  pyruvate dehydrogenase: phosphorylation 
B)  isocitrate dehydrogenase: AMP 
C)  α-ketoglutarate dehydrogenase: NAD+ 
D)  citrate synthase: acetyl CoA 
E)  none of the above are correct A

Question 3

Which is NOT true of citrate synthase?

Accepted Answer

A)  it catalyzes the first reaction in the TCA cycle 
B)  it is not regulated 
C)  OAA and acetyl-CoA bind to the active sites 
D)  the citrate synthase reaction liberates a relatively large amount of energy 
E)  all of the above are true 
A)  it catalyzes the first reaction in the TCA cycle 
B)  it is not regulated 
C)  OAA and acetyl-CoA bind to the active sites 
D)  the citrate synthase reaction liberates a relatively large amount of energy 
E)  all of the above are true B

Question 4

Citrate synthase is a ____ with binding of ____ inducing a conformational change ____ the binding of acetyl-CoA, and ____ is an allosteric inhibitor.

Accepted Answer

A)  dimer; OAA; increasing; NADH 
B)  dimer; OAA; decreasing; NADH 
C)  tetramer; OAA; decreasing; NAD+ 
D)  monomer; pyruvate; decreasing; ATP 
E)  monomer; pyruvate; increasing; ATP 
A)  dimer; OAA; increasing; NADH 
B)  dimer; OAA; decreasing; NADH 
C)  tetramer; OAA; decreasing; NAD+ 
D)  monomer; pyruvate; decreasing; ATP 
E)  monomer; pyruvate; increasing; ATP

Question 5

The glyoxylate cycle reaction that is catalyzed by malate synthase involves the condensation of acetyl CoA with _____. The mechanism is most similar to the TCA cycle enzyme _____.

Accepted Answer

A)  succinate; fumarase 
B)  isocitrate; succinyl-CoA synthetase 
C)  glyoxylate; citrate synthase 
D)  oxaloacetate; aconitase 
E)  acetyl CoA; isocitrate lyase 
A)  succinate; fumarase 
B)  isocitrate; succinyl-CoA synthetase 
C)  glyoxylate; citrate synthase 
D)  oxaloacetate; aconitase 
E)  acetyl CoA; isocitrate lyase

Question 6

All are true statements for the glyoxylate pathway EXCEPT:

Accepted Answer

A)  the glyoxylate pathway enzymes are found in the glyoxysomes. 
B)  although glyoxysomes are found in germinating seeds, they disappear after a plant begins photosynthesis. 
C)  glyoxysomes contain all of the enzymes for the glyoxylate cycle. 
D)  bypasses the oxidative-decarboxylation steps of the TCA cycle. 
E)  isocitrate is routed through isocitrate lyase and malate synthase. 
A)  the glyoxylate pathway enzymes are found in the glyoxysomes. 
B)  although glyoxysomes are found in germinating seeds, they disappear after a plant begins photosynthesis. 
C)  glyoxysomes contain all of the enzymes for the glyoxylate cycle. 
D)  bypasses the oxidative-decarboxylation steps of the TCA cycle. 
E)  isocitrate is routed through isocitrate lyase and malate synthase.

Question 7

The pyruvate dehydrogenase complex contains three multimeric enzymes (ETA, EPDH, and EDLD). All are properties of EPDH EXCEPT:

Accepted Answer

A)  It uses thiamin pyrophosphate as a catalytic coenzyme. 
B)  It oxidatively decarboxylates pyruvate. 
C)  It binds NAD+ in its active site. 
D)  It transfers an acetyl group to lipoamide of ETA. 
E)  It forms a hydroxyethyl-TPP intermediate. 
A)  It uses thiamin pyrophosphate as a catalytic coenzyme. 
B)  It oxidatively decarboxylates pyruvate. 
C)  It binds NAD+ in its active site. 
D)  It transfers an acetyl group to lipoamide of ETA. 
E)  It forms a hydroxyethyl-TPP intermediate.

Question 8

Which of the following enzymes catalyzes an endergonic step of the citric acid cycle?

Accepted Answer

A)  citrate synthase 
B)  malate dehydrogenase 
C)  α-ketoglutarate dehydrogenase 
D)  isocitrate dehydrogenase 
E)  none of the above 
A)  citrate synthase 
B)  malate dehydrogenase 
C)  α-ketoglutarate dehydrogenase 
D)  isocitrate dehydrogenase 
E)  none of the above

Question 9

All of the following are inhibitors of citrate synthase EXCEPT:

Accepted Answer

A)  acetyl-CoA 
B)  NADH 
C)  succinyl-CoA 
D)  ATP 
E)  all are inhibitors 
A)  acetyl-CoA 
B)  NADH 
C)  succinyl-CoA 
D)  ATP 
E)  all are inhibitors

Question 10

The ____ of pyruvate to acetyl-CoA is catalyzed by ____.

Accepted Answer

A)  dehydration; pyruvate dehydration complex 
B)  decarboxylation; pyruvate dehydrogenase complex 
C)  decarboxylation; pyruvate decarboxylase 
D)  transacylation; pyruvate transacylase 
E)  none of the above. 
A)  dehydration; pyruvate dehydration complex 
B)  decarboxylation; pyruvate dehydrogenase complex 
C)  decarboxylation; pyruvate decarboxylase 
D)  transacylation; pyruvate transacylase 
E)  none of the above.

Question 11

An essential feature of the glyoxylate cycle, which is not associated with the TCA cycle is:

Accepted Answer

A)  it utilizes condensation of acetyl-CoA with glyoxylate 
B)  each complete cycle produces a net gain of two 4-carbon molecules 
C)  it occurs in chloroplasts and the mitochondria of plant seeds 
D)  mammals use the glyoxylate cycle for gluconeogenesis 
E)  it is a reductive pathway that utilizes NADPH as an electron source 
A)  it utilizes condensation of acetyl-CoA with glyoxylate 
B)  each complete cycle produces a net gain of two 4-carbon molecules 
C)  it occurs in chloroplasts and the mitochondria of plant seeds 
D)  mammals use the glyoxylate cycle for gluconeogenesis 
E)  it is a reductive pathway that utilizes NADPH as an electron source

Question 12

Citrate must be isomerized to isocitrate because the ____ group of citrate is not oxidizable, but the ____ group of isocitrate can be oxidized.

Accepted Answer

A)  ketone; primary alcohol 
B)  tertiary alcohol; secondary alcohol 
C)  ketone; secondary alcohol 
D)  aldehyde; primary alcohol 
E)  secondary alcohol; ketone 
A)  ketone; primary alcohol 
B)  tertiary alcohol; secondary alcohol 
C)  ketone; secondary alcohol 
D)  aldehyde; primary alcohol 
E)  secondary alcohol; ketone

Question 13

The correct sequence of steps between succinyl-CoA and ATP in mammals to "preserve" the energy of the thioester bond are:
A.succinyl-phosphatE.
B.phosphohistidinE.
C.GTP.
D.Acetyl-CoA.

Accepted Answer

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

Question 14

The following statements are correct about the reaction catalyzed by the pyruvate dehydrogenase complex EXCEPT:

Accepted Answer

A)  it is the link between glycolysis and the TCA cycle 
B)  The activity of the complex is regulated by the phosphorylation of EPDH. 
C)  NAD+ is the direct oxidant of reduced lipoamide. 
D)  An FAD is covalently linked to the EDLD, the lipoamide dehydrogenase component. 
E)  Although EPDH is called "pyruvate dehydrogenase" it is not a dehydrogenase. 
A)  it is the link between glycolysis and the TCA cycle 
B)  The activity of the complex is regulated by the phosphorylation of EPDH. 
C)  NAD+ is the direct oxidant of reduced lipoamide. 
D)  An FAD is covalently linked to the EDLD, the lipoamide dehydrogenase component. 
E)  Although EPDH is called "pyruvate dehydrogenase" it is not a dehydrogenase.

Question 15

In mammalian tissues, isocitrate dehydrogenase is allosterically stimulated by:

Accepted Answer

A)  high NAD+/NADH and high ADP/ATP ratios. 
B)  low ADP/ATP and low NAD+/NADH ratios. 
C)  high NAD+/NADH and low ADP/ATP ratios. 
D)  low NAD+/NADH and high ADP/ATP ratios. 
E)  none of the above. 
A)  high NAD+/NADH and high ADP/ATP ratios. 
B)  low ADP/ATP and low NAD+/NADH ratios. 
C)  high NAD+/NADH and low ADP/ATP ratios. 
D)  low NAD+/NADH and high ADP/ATP ratios. 
E)  none of the above.

Question 16

The succinate dehydrogenase mechanism involves the ____ of succinate, which is exergonic and can be used to provide for the ____.

Accepted Answer

A)  oxidation; reduction of NAD+ 
B)  reduction; oxidation of NAD+ 
C)  oxidation; reduction of [FAD] 
D)  reduction; oxidation of [FAD] 
E)  none are true 
A)  oxidation; reduction of NAD+ 
B)  reduction; oxidation of NAD+ 
C)  oxidation; reduction of [FAD] 
D)  reduction; oxidation of [FAD] 
E)  none are true

Question 17

Which of the following statements regarding the glyoxylate cycle is true?

Accepted Answer

A)  the process takes place in the mitochondria 
B)  two molecules of acetyl CoA can be converted to one molecule of oxaloacetate 
C)  isocitrate dehydrogenase and malate dehydrogenase are not used 
D)  the primary role is to allow for the synthesis of amino acids from fatty acids 
E)  none of the above 
A)  the process takes place in the mitochondria 
B)  two molecules of acetyl CoA can be converted to one molecule of oxaloacetate 
C)  isocitrate dehydrogenase and malate dehydrogenase are not used 
D)  the primary role is to allow for the synthesis of amino acids from fatty acids 
E)  none of the above

Question 18

The two step reaction catalyzed by isocitrate dehydrogenase involves:
A.β-decarboxylation expelling the α-keto carboxyl as CO2.
B.oxidation of the C-2 alcohol of isocitrate to form oxalosuccinatE.
C.oxidation of the C-2 alcohol to form oxaloacetatE.
D.β-elimination expelling the central carboxyl group as CO2.

Accepted Answer

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

Question 19

The coenzymes listed below are associated with α-ketoglutarate dehydrogenase complex EXCEPT:

Accepted Answer

A)  [FAD]. 
B)  TPP. 
C)  lipoamide. 
D)  NAD+. 
E)  biotin. 
A)  [FAD]. 
B)  TPP. 
C)  lipoamide. 
D)  NAD+. 
E)  biotin.

Question 20

Explain the role of the iron-sulfur cluster of aconitase in the reversible conversion of citrate to isocitrate in the tricarboxylic acid cycle.​

Accepted Answer

Aconitase contains an iron-sulfur cluste

Exam 19: The Tricarboxylic Acid Cycle

The isocitrate lyase catalyzed reaction cleaves isocitrate into:

Which of the following is correctly paired with its inhibitor?

Which is NOT true of citrate synthase?

Citrate synthase is a ____ with binding of ____ inducing a conformational change ____ the binding of acetyl-CoA, and ____ is an allosteric inhibitor.

The glyoxylate cycle reaction that is catalyzed by malate synthase involves the condensation of acetyl CoA with _____. The mechanism is most similar to the TCA cycle enzyme _____.

All are true statements for the glyoxylate pathway EXCEPT:

The pyruvate dehydrogenase complex contains three multimeric enzymes (ETA, EPDH, and EDLD). All are properties of EPDH EXCEPT:

Which of the following enzymes catalyzes an endergonic step of the citric acid cycle?

All of the following are inhibitors of citrate synthase EXCEPT:

The ____ of pyruvate to acetyl-CoA is catalyzed by ____.

An essential feature of the glyoxylate cycle, which is not associated with the TCA cycle is:

Citrate must be isomerized to isocitrate because the ____ group of citrate is not oxidizable, but the ____ group of isocitrate can be oxidized.

The correct sequence of steps between succinyl-CoA and ATP in mammals to "preserve" the energy of the thioester bond are: A.succinyl-phosphatE. B.phosphohistidinE. C.GTP. D.Acetyl-CoA.

The following statements are correct about the reaction catalyzed by the pyruvate dehydrogenase complex EXCEPT:

In mammalian tissues, isocitrate dehydrogenase is allosterically stimulated by:

The succinate dehydrogenase mechanism involves the ____ of succinate, which is exergonic and can be used to provide for the ____.

Which of the following statements regarding the glyoxylate cycle is true?

The coenzymes listed below are associated with α-ketoglutarate dehydrogenase complex EXCEPT:

Explain the role of the iron-sulfur cluster of aconitase in the reversible conversion of citrate to isocitrate 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

Citrate synthase is a with binding of inducing a conformational change the binding of acetyl-CoA, and is an allosteric inhibitor.

The glyoxylate cycle reaction that is catalyzed by malate synthase involves the condensation of acetyl CoA with _. The mechanism is most similar to the TCA cycle enzyme _.

The pyruvate dehydrogenase complex contains three multimeric enzymes (E_TA, E_PDH, and E_DLD). All are properties of E_PDH EXCEPT:

The of pyruvate to acetyl-CoA is catalyzed by .

Citrate must be isomerized to isocitrate because the group of citrate is not oxidizable, but the group of isocitrate can be oxidized.

The succinate dehydrogenase mechanism involves the of succinate, which is exergonic and can be used to provide for the .

Explain the role of the iron-sulfur cluster of aconitase in the reversible conversion of citrate to isocitrate in the tricarboxylic acid cycle.