Question 1

Which of the following is an essential feature of the glyoxylate cycle that is NOT associated with the TCA cycle?

Accepted Answer

A) It utilizes condensation of acetyl-CoA with succinate. 
B) It can produce a net synthesis of 4-carbon units,which are TCA cycle intermediates,from acetyl-CoAs. 
C) It occurs in chloroplasts. 
D) Mammals use the glyoxylate cycle for gluconeogenesis. 
A) It utilizes condensation of acetyl-CoA with succinate. 
B) It can produce a net synthesis of 4-carbon units,which are TCA cycle intermediates,from acetyl-CoAs. 
C) It occurs in chloroplasts. 
D) Mammals use the glyoxylate cycle for gluconeogenesis. A

Question 2

Which alcohol group of isocitrate is oxidizable?

Accepted Answer

A) primary 
B) secondary 
C) tertiary 
D) quaternary 
A) primary 
B) secondary 
C) tertiary 
D) quaternary B

Question 3

Which coenzyme is involved in the reactions carried out by the pyruvate dehydrogenase complex?

Accepted Answer

A) NADH 
B) acetyl-CoASH 
C) TPP 
D) [FADH₂] 
A) NADH 
B) acetyl-CoASH 
C) TPP 
D) [FADH₂] C

Question 4

Which TCA cycle enzyme is inhibited by fluorocitrate,the product of citrate synthase's action on fluoroacetate?

Accepted Answer

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

Question 5

Which molecule is an allosteric inhibitor of citrate synthase?

Accepted Answer

A) NADH 
B) OAA 
C) [FADH₂] 
D) ATP 
A) NADH 
B) OAA 
C) [FADH₂] 
D) ATP

Question 6

Which feature of electron transport is NOT involved in the succinate dehydrogenase reaction mechanism?

Accepted Answer

A) coenzyme Q (UQ) 
B) NADH 
C) [FAD] 
D) iron-sulfur clusters 
A) coenzyme Q (UQ) 
B) NADH 
C) [FAD] 
D) iron-sulfur clusters

Question 7

Which of the following statements is NOT correct about the reaction catalyzed by the pyruvate dehydrogenase complex?

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 the pyruvate dehydrogenase complex. 
C) NAD⁺ is the direct oxidant of reduced lipoamide. 
D) An FAD is covalently linked to the EDLD,the lipoamide dehydrogenase component. 
A) It is the link between glycolysis and the TCA cycle. 
B) The activity of the complex is regulated by the phosphorylation of the pyruvate dehydrogenase complex. 
C) NAD⁺ is the direct oxidant of reduced lipoamide. 
D) An FAD is covalently linked to the EDLD,the lipoamide dehydrogenase component.

Question 8

Which is NOT a feature of citrate synthase?

Accepted Answer

A) It catalyzes the first reaction in the TCA cycle. 
B) OAA and acetyl-CoA bind to the active sites. 
C) The citrate synthase reaction liberates a relatively large amount of energy. 
D) It is not regulated. 
A) It catalyzes the first reaction in the TCA cycle. 
B) OAA and acetyl-CoA bind to the active sites. 
C) The citrate synthase reaction liberates a relatively large amount of energy. 
D) It is not regulated.

Question 9

What is the ∆G°' value for citrate synthase?

Accepted Answer

A) It is largely positive. 
B) It is nearly zero. 
C) It is not measurable. 
D) It is largely negative. 
A) It is largely positive. 
B) It is nearly zero. 
C) It is not measurable. 
D) It is largely negative.

Question 10

Which molecules are generated when isocitrate lyase cleaves isocitrate?

Accepted Answer

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

Question 11

Which of the following is NOT a principal allosteric regulator of TCA cycle activity?

Accepted Answer

A) [FADH₂] 
B) NADH 
C) acetyl-CoA 
D) ATP 
A) [FADH₂] 
B) NADH 
C) acetyl-CoA 
D) ATP

Question 12

Which of the following is NOT correct for aconitase?

Accepted Answer

A) Iron atom acts as a Lewis acid. 
B) Equilibrium favours isocitrate. 
C) Aconitase contains an iron-sulfur cluster. 
D) One Fe3+ coordinates with C-3 carbonyl and hydroxyl group of citrate. 
A) Iron atom acts as a Lewis acid. 
B) Equilibrium favours isocitrate. 
C) Aconitase contains an iron-sulfur cluster. 
D) One Fe3+ coordinates with C-3 carbonyl and hydroxyl group of citrate.

Question 13

Which of the following is NOT a feature of the fumarase catalyzed reaction?

Accepted Answer

A) Fumarate is hydrated. 
B) The reaction is stereospecific for a cis product. 
C) The reaction involved is similar to that carried out by aconitase. 
D) L-Malate is the product. 
A) Fumarate is hydrated. 
B) The reaction is stereospecific for a cis product. 
C) The reaction involved is similar to that carried out by aconitase. 
D) L-Malate is the product.

Question 14

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

Accepted Answer

A) pyruvate → OAA 
B) OAA → PEP 
C) citrate → OAA + acetyl-CoA 
D) Asp → α-ketoglutarate 
A) pyruvate → OAA 
B) OAA → PEP 
C) citrate → OAA + acetyl-CoA 
D) Asp → α-ketoglutarate

Question 15

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

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. 
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.

Question 16

What are the anaplerotic reactions associated with the TCA cycle a result of?

Accepted Answer

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

Question 17

Which of the following is NOT correct for pyruvate carboxylase?

Accepted Answer

A) It carries out an anaplerotic reaction. 
B) It resides in mitochondria of plants,but not animals. 
C) It contains covalently bound biotin. 
D) It has an absolute allosteric requirement for acetyl-CoA. 
A) It carries out an anaplerotic reaction. 
B) It resides in mitochondria of plants,but not animals. 
C) It contains covalently bound biotin. 
D) It has an absolute allosteric requirement for acetyl-CoA.

Question 18

Which of these enzymes catalyzes the only reaction of the citric acid cycle that provides substrate-level phosphorylation?

Accepted Answer

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

Question 19

Energy is derived from the succinate dehydrogenase mechanism.What process is the energy used for?

Accepted Answer

A) reduction of NAD⁺ 
B) oxidation of NAD⁺ 
C) reduction of [FAD] 
D) oxidation of [FAD] 
A) reduction of NAD⁺ 
B) oxidation of NAD⁺ 
C) reduction of [FAD] 
D) oxidation of [FAD]

Question 20

Why is it crucial that regulation occur at pyruvate dehydrogenase?

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. 
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.

Exam 18: The Tricarboxylic Acid Cycle

Which of the following is an essential feature of the glyoxylate cycle that is NOT associated with the TCA cycle?

Which alcohol group of isocitrate is oxidizable?

Which coenzyme is involved in the reactions carried out by the pyruvate dehydrogenase complex?

Which TCA cycle enzyme is inhibited by fluorocitrate,the product of citrate synthase's action on fluoroacetate?

Which molecule is an allosteric inhibitor of citrate synthase?

Which feature of electron transport is NOT involved in the succinate dehydrogenase reaction mechanism?

Which of the following statements is NOT correct about the reaction catalyzed by the pyruvate dehydrogenase complex?

Which is NOT a feature of citrate synthase?

What is the ∆G°' value for citrate synthase?

Which molecules are generated when isocitrate lyase cleaves isocitrate?

Which of the following is NOT a principal allosteric regulator of TCA cycle activity?

Which of the following is NOT correct for aconitase?

Which of the following is NOT a feature of the fumarase catalyzed reaction?

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

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

What are the anaplerotic reactions associated with the TCA cycle a result of?

Which of the following is NOT correct for pyruvate carboxylase?

Which of these enzymes catalyzes the only reaction of the citric acid cycle that provides substrate-level phosphorylation?

Energy is derived from the succinate dehydrogenase mechanism.What process is the energy used for?

Why is it crucial that regulation occur at pyruvate dehydrogenase?

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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