Question 1

Which of the following is NOT a coenzyme for the α-ketoglutarate dehydrogenase complex?

Accepted Answer

A) TPP 
B) lipoamide 
C) NAD⁺ 
D) biotin 
A) TPP 
B) lipoamide 
C) NAD⁺ 
D) biotin

Question 2

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 
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

Question 3

Which of the following is NOT correct about the reaction catalyzed by citrate synthase?

Accepted Answer

A) Citrate synthase is allosterically activated by ATP. 
B) The complete chemical equation is: 
oxaloacetate + acetyl-CoA + H?O 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. 
A) Citrate synthase is allosterically activated by ATP. 
B) The complete chemical equation is: 
oxaloacetate + acetyl-CoA + H?O 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.

Question 4

Which molecule is generated between succinyl-CoA and ATP in mammals to "preserve" the energy of the thioester bond?

Accepted Answer

A) a-ketoglutarate 
B) phosphohistidine 
C) citrate 
D) acetyl-CoA 
A) a-ketoglutarate 
B) phosphohistidine 
C) citrate 
D) acetyl-CoA

Question 5

Which carbon molecule enters the TCA cycle and exits as CO₂,with metabolic energy captured as ATP,NADH,and [FADH₂]?

Accepted Answer

A) malonate 
B) succinyl-CoA 
C) acetyl-CoA 
D) malonyl-CoA 
A) malonate 
B) succinyl-CoA 
C) acetyl-CoA 
D) malonyl-CoA

Question 6

Which of the following is NOT correct for the glyoxylate pathway?

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 the enzymes for the glyoxylate cycle. 
D) The glyoxylate pathway bypasses the oxidative-decarboxylation steps of the TCA cycle. 
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 the enzymes for the glyoxylate cycle. 
D) The glyoxylate pathway bypasses the oxidative-decarboxylation steps of the TCA cycle.

Question 7

The pyruvate dehydrogenase complex contains 3 multimeric enzymes.Which of the following is NOT a property of the complex?

Accepted Answer

A) It uses thiamine pyrophosphate as a catalytic coenzyme. 
B) It oxidatively decarboxylates pyruvate. 
C) It binds NAD⁺ in its active site. 
D) It forms a hydroxyethyl-TPP intermediate. 
A) It uses thiamine pyrophosphate as a catalytic coenzyme. 
B) It oxidatively decarboxylates pyruvate. 
C) It binds NAD⁺ in its active site. 
D) It forms a hydroxyethyl-TPP intermediate.

Question 8

Which of these enzymes catalyzes the reaction CO₂ + PEP + GDP ↔ OAA + GTP?

Accepted Answer

A) PEP carboxylase 
B) PEP carboxykinase 
C) malic enzyme 
D) pyruvate carboxylase 
A) PEP carboxylase 
B) PEP carboxykinase 
C) malic enzyme 
D) pyruvate carboxylase

Question 9

Which enzyme carries out a reaction of the citric acid cycle with the largest negative ∆G value?

Accepted Answer

A) citrate synthase 
B) succinyl-CoA synthetase 
C) succinyl-CoA dehydrogenase 
D) malate dehydrogenase 
A) citrate synthase 
B) succinyl-CoA synthetase 
C) succinyl-CoA dehydrogenase 
D) malate dehydrogenase

Question 10

Which of the following allosterically stimulate mammalian isocitrate dehydrogenase?

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 
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

Question 11

Which of the following is NOT part of the 2-step reaction catalyzed by isocitrate dehydrogenase?

Accepted Answer

A) ?-decarboxylation expelling the a-keto carboxyl as CO? 
B) oxidation of the C-2 alcohol of isocitrate to form oxalosuccinate 
C) oxidation of the C-2 alcohol to form oxaloacetate 
D) ?-decarboxylation expelling the central carboxyl group as CO? 
A) ?-decarboxylation expelling the a-keto carboxyl as CO? 
B) oxidation of the C-2 alcohol of isocitrate to form oxalosuccinate 
C) oxidation of the C-2 alcohol to form oxaloacetate 
D) ?-decarboxylation expelling the central carboxyl group as CO?

Question 12

Which of the following is an inhibitor of citrate synthase?

Accepted Answer

A) acetyl-CoA 
B) [FADH₂] 
C) succinyl-CoA 
D) ADP 
A) acetyl-CoA 
B) [FADH₂] 
C) succinyl-CoA 
D) ADP

Question 13

Where do glycolysis and the TCA cycle,respectively,occur in eukaryotic cells?

Accepted Answer

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

Question 14

How many NADH molecules are produced in the TCA cycle per molecule of acetyl-CoA oxidized?

Accepted Answer

A) 1 
B) 2 
C) 3 
D) 4 
A) 1 
B) 2 
C) 3 
D) 4

Question 15

Which of the following is NOT a characteristic of succinyl-CoA synthetase?

Accepted Answer

A) Succinyl-CoA can be used to drive phosphorylation of GDP or ADP. 
B) The enzyme is named for the forward reaction. 
C) It provides an example of substrate-level phosphorylation. 
D) Succinyl-phosphate is an intermediate in the reaction catalyzed by succinyl-CoA synthetase. 
A) Succinyl-CoA can be used to drive phosphorylation of GDP or ADP. 
B) The enzyme is named for the forward reaction. 
C) It provides an example of substrate-level phosphorylation. 
D) Succinyl-phosphate is an intermediate in the reaction catalyzed by succinyl-CoA synthetase.

Question 16

Which of the following is NOT a characteristic of isocitrate dehydrogenase?

Accepted Answer

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

Question 17

Which enzyme is allosterically activated when acetyl-CoA levels exceed oxaloacetate (OAA)supply?

Accepted Answer

A) citrate synthase 
B) malate dehydrogenase 
C) citrate synthase. 
D) pyruvate carboxylase. 
A) citrate synthase 
B) malate dehydrogenase 
C) citrate synthase. 
D) pyruvate carboxylase.

Question 18

The oxidation of malate to oxaloacetate is not thermodynamically favoured under standard conditions.Why does it occur?

Accepted Answer

A) It involves substrate-level phosphorylation. 
B) Oxaloacetate is used in the next reaction,which has a negative ∆G. 
C) It is coupled with ATP hydrolysis. 
D) It is coupled with a strong reduction. 
A) It involves substrate-level phosphorylation. 
B) Oxaloacetate is used in the next reaction,which has a negative ∆G. 
C) It is coupled with ATP hydrolysis. 
D) It is coupled with a strong reduction.

Question 19

Which enzyme catalyzes citrate isomerization to isocitrate by abstracting water from citrate?

Accepted Answer

A) citrate isomerase 
B) citrate synthase 
C) aconitase 
D) isocitrate dehydrogenase 
A) citrate isomerase 
B) citrate synthase 
C) aconitase 
D) isocitrate dehydrogenase

Question 20

Which enzyme is analogous to the multi-enzyme complex α-ketoglutarate?

Accepted Answer

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

Exam 18: The Tricarboxylic Acid Cycle

Which of the following is NOT a coenzyme for the α-ketoglutarate dehydrogenase complex?

Which enzymes of the TCA cycle catalyze oxidative decarboxylation reactions?

Which of the following is NOT correct about the reaction catalyzed by citrate synthase?

Which molecule is generated between succinyl-CoA and ATP in mammals to "preserve" the energy of the thioester bond?

Which carbon molecule enters the TCA cycle and exits as CO₂,with metabolic energy captured as ATP,NADH,and [FADH₂]?

Which of the following is NOT correct for the glyoxylate pathway?

The pyruvate dehydrogenase complex contains 3 multimeric enzymes.Which of the following is NOT a property of the complex?

Which of these enzymes catalyzes the reaction CO₂ + PEP + GDP ↔ OAA + GTP?

Which enzyme carries out a reaction of the citric acid cycle with the largest negative ∆G value?

Which of the following allosterically stimulate mammalian isocitrate dehydrogenase?

Which of the following is NOT part of the 2-step reaction catalyzed by isocitrate dehydrogenase?

Which of the following is an inhibitor of citrate synthase?

Where do glycolysis and the TCA cycle,respectively,occur in eukaryotic cells?

How many NADH molecules are produced in the TCA cycle per molecule of acetyl-CoA oxidized?

Which of the following is NOT a characteristic of succinyl-CoA synthetase?

Which of the following is NOT a characteristic of isocitrate dehydrogenase?

Which enzyme is allosterically activated when acetyl-CoA levels exceed oxaloacetate (OAA)supply?

The oxidation of malate to oxaloacetate is not thermodynamically favoured under standard conditions.Why does it occur?

Which enzyme catalyzes citrate isomerization to isocitrate by abstracting water from citrate?

Which enzyme is analogous to the multi-enzyme complex α-ketoglutarate?

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

Water: the Medium of Life

Thermodynamics of Biological Systems

Amino Acids

Proteins: Their Primary Structure and Biological Functions

Proteins: Secondary, tertiary, and Quaternary Structure

Carbohydrates and the Glycoconjugates of Cell Surfaces

Lipids

Lipid Biosynthesis

Membranes and Membrane Transport

The Reception and Transmission of Extracellular Information

Enzymes Kinetics and Specificity

Mechanisms of Enzyme Action

Enzyme Regulation

Molecular Motors

Nutrition and the Organization of Metabolism

Glycolysis

Electron Transport and Oxidative Phosphorylation

Photosynthesis

Gluconeogenesis, glycogen Metabolism, and the Pentose Phosphate Pathway

Fatty Acid Catabolism

Nitrogen Acquisition and Amino Acid Metabolism

Nucleotides and Nucleic Acids

Structure of Nucleic Acids

Synthesis and Degradation of Nucleotides

Recombinant Dna: Cloning and Creation of Chimeric Genes

DNA Metabolism: Replication, recombination, and Repair

Transcription and the Regulation of Gene Expression

Protein Synthesis

Post-Transcriptional Regulation of Gene Expression

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

Metabolic Integration and Organ Specialization

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