Question 1

Most organisms cannot convert ______________________ into glucose because of the two decarboxylations in the citric acid cycle.

Accepted Answer

acetyl CoA or fatty acids

Question 2

________________ is the first citric acid cycle intermediate to be oxidized.

Accepted Answer

Isocitrate

Question 3

When intermediates of the citric acid cycle are depleted by biosynthetic pathways,_____ reactions are used to replenish the citric acid cycle intermediates.

Accepted Answer

A)  anaplerotic 
B)  amphibolic 
C)  amphoteric 
D)  biosynthetic 
E)  None of the answers is correct. 
A)  anaplerotic 
B)  amphibolic 
C)  amphoteric 
D)  biosynthetic 
E)  None of the answers is correct. A

Question 4

What is/are the chemical change(s)involved in the conversion of citrate into isocitrate?

Accepted Answer

A)  hydration followed by dehydration 
B)  dehydration followed by hydration 
C)  oxidation followed by reduction 
D)  reduction followed by oxidation 
E)  None of the answers is correct. 
A)  hydration followed by dehydration 
B)  dehydration followed by hydration 
C)  oxidation followed by reduction 
D)  reduction followed by oxidation 
E)  None of the answers is correct.

Question 5

Which of the following vitamins are precursors to coenzymes that are necessary for the formation of acetyl CoA from pyruvate?

Accepted Answer

A)  thiamine, riboflavin, niacin, lipoic acid, and pantothenic acid 
B)  thiamine, riboflavin, niacin, lipoic acid, pantothenic acid, and biotin 
C)  thiamine, riboflavin, niacin, and biotin 
D)  thiamine, riboflavin, and folic acid 
E)  None of the answers is correct. 
A)  thiamine, riboflavin, niacin, lipoic acid, and pantothenic acid 
B)  thiamine, riboflavin, niacin, lipoic acid, pantothenic acid, and biotin 
C)  thiamine, riboflavin, niacin, and biotin 
D)  thiamine, riboflavin, and folic acid 
E)  None of the answers is correct.

Question 6

In which reaction is GTP (or ATP)directly formed in the citric acid cycle?

Accepted Answer

A)  conversion of succinyl CoA to succinate 
B)  decarboxylation of $\alpha$-ketoglutarate 
C)  conversion of isocitrate to $\alpha$-ketoglutarate 
D)  condensation of acetyl-CoA and oxaloacetate 
E)  None of the answers is correct. 
A)  conversion of succinyl CoA to succinate 
B)  decarboxylation of $\alpha$-ketoglutarate 
C)  conversion of isocitrate to $\alpha$-ketoglutarate 
D)  condensation of acetyl-CoA and oxaloacetate 
E)  None of the answers is correct.

Question 7

E1 of the pyruvate dehydrogenase complex requires the coenzyme ________________ for proper activity.

Accepted Answer

thiamine p

Question 8

Which of the following functions as a "flexible swinging arm" when it transfers the reaction intermediate from one active site to the next?

Accepted Answer

A)  FAD 
B)  NAD+ 
C)  lipoamide 
D)  thiamine pyrophosphate 
E)  coenzyme A 
A)  FAD 
B)  NAD+ 
C)  lipoamide 
D)  thiamine pyrophosphate 
E)  coenzyme A

Question 9

Where does the citric acid cycle take place in the cell?

Accepted Answer

A)  cytosol 
B)  mitochondria 
C)  nucleus 
D)  endoplasmic reticulum 
E)  lysosome 
A)  cytosol 
B)  mitochondria 
C)  nucleus 
D)  endoplasmic reticulum 
E)  lysosome

Question 10

Give the reaction in the citric acid cycle by which the energy is conserved in the formation of a phosphoanhydride bond by substrate level phosphorylation.Give the name of the enzyme that catalyzes this reaction and give the structures of the reactants and products of this reaction.

Accepted Answer

The answer of Give the reaction in the citric acid...

Question 11

Explain why a GTP is energetically equivalent to an ATP in metabolism.

Accepted Answer

The enzyme nucleoside diphosphokinase re

Question 12

The ?G??=-21 kJ mol-1 for the reaction catalyzed by isocitrate dehydrogenase,yet the ?G?? = +29.7 kJ mol-1 for the reaction catalyzed by malate dehydrogenase.Both of these reactions involve the oxidation of a secondary alcohol.Give an explanation as to why the oxidation of isocitrate is so exergonic.

Accepted Answer

The oxidation of isocitrate produces oxa

Question 13

What is the enzyme-bound intermediate in the conversion of citrate and isocitrate?

Accepted Answer

A)  oxalosuccinate 
B)  dihydrocitrate 
C)  cis-aconitate 
D)  hydroxyethyl-TPP 
E)  fumarate 
A)  oxalosuccinate 
B)  dihydrocitrate 
C)  cis-aconitate 
D)  hydroxyethyl-TPP 
E)  fumarate

Question 14

Why is it necessary that there be a mechanism to replenish oxaloacetate?

Accepted Answer

During periods of biosynthesis,oxaloacet

Question 15

How does the term "mad as a hatter" realistically reflect the condition?

Accepted Answer

Hatters used mercury in their craft.Freq

Question 16

E2 of the pyruvate dehydrogenase complex contains a lipoyl group that is covalently attached to a _______________ residue of the enzyme.

Accepted Answer

The answer of E2 of the pyruvate dehydrogenase complex contains...

Question 17

How many ATP equivalents are produced from the total oxidation of one pyruvate to three CO2?

Accepted Answer

The total oxidation of one pyruvate by p

Question 18

Which of the following is considered a product of the citric acid cycle?

Accepted Answer

A)  acetate 
B)  $\alpha$-ketoglutarate 
C)  NAD+ 
D)  oxaloacetate 
E)  carbon dioxide 
A)  acetate 
B)  $\alpha$-ketoglutarate 
C)  NAD+ 
D)  oxaloacetate 
E)  carbon dioxide

Question 19

For a single rotation of the Krebs cycle,are the acetyl carbons that enter the citric acid cycle the exact same carbons that leave as CO2? Briefly explain.

Accepted Answer

No,the carbons are different.The carbons

Question 20

What cycle allows for the net synthesis of glucose from acetyl-CoA?

Accepted Answer

A)  Calvin cycle 
B)  glyoxylate cycle 
C)  C4 pathway 
D)  urea cycle 
E)  None of the answers is correct. 
A)  Calvin cycle 
B)  glyoxylate cycle 
C)  C4 pathway 
D)  urea cycle 
E)  None of the answers is correct.

Exam 17: The Citric Acid Cycle

Most organisms cannot convert ______________________ into glucose because of the two decarboxylations in the citric acid cycle.

________________ is the first citric acid cycle intermediate to be oxidized.

When intermediates of the citric acid cycle are depleted by biosynthetic pathways,_____ reactions are used to replenish the citric acid cycle intermediates.

What is/are the chemical change(s)involved in the conversion of citrate into isocitrate?

Which of the following vitamins are precursors to coenzymes that are necessary for the formation of acetyl CoA from pyruvate?

In which reaction is GTP (or ATP)directly formed in the citric acid cycle?

E1 of the pyruvate dehydrogenase complex requires the coenzyme ________________ for proper activity.

Which of the following functions as a "flexible swinging arm" when it transfers the reaction intermediate from one active site to the next?

Where does the citric acid cycle take place in the cell?

Give the reaction in the citric acid cycle by which the energy is conserved in the formation of a phosphoanhydride bond by substrate level phosphorylation.Give the name of the enzyme that catalyzes this reaction and give the structures of the reactants and products of this reaction.

Explain why a GTP is energetically equivalent to an ATP in metabolism.

What is the enzyme-bound intermediate in the conversion of citrate and isocitrate?

Why is it necessary that there be a mechanism to replenish oxaloacetate?

How does the term "mad as a hatter" realistically reflect the condition?

E2 of the pyruvate dehydrogenase complex contains a lipoyl group that is covalently attached to a _______________ residue of the enzyme.

How many ATP equivalents are produced from the total oxidation of one pyruvate to three CO2?

Which of the following is considered a product of the citric acid cycle?

For a single rotation of the Krebs cycle,are the acetyl carbons that enter the citric acid cycle the exact same carbons that leave as CO2? Briefly explain.

What cycle allows for the net synthesis of glucose from acetyl-CoA?

Biochemistry: An Evolving Science

Protein Composition and Structure

Exploring Proteins and Proteomes

DNA, RNA, and the Flow of Genetic Information

Exploring Genes and Genomes

Exploring Evolution and Bioinformatics

Hemoglobin: a Portrait of a Protein in Action

Enzymes: Basic Concepts and Kinetics

Catalytic Strategies

Regulatory Strategies

Carbohydrates

Lipids and Cell Membranes

Membrane Channels and Pumps

Signal-Transduction Pathways

Metabolism: Basic Concepts and Design

Glycolysis and Gluconeogenesis

Oxidative Phosphorylation

The Light Reactions of Photosynthesis

The Calvin Cycle and the Pentose Phosphate Pathway

Glycogen Metabolism

Fatty Acid Metabolism

Protein Turnover and Amino Acid Catabolism

The Biosynthesis of Amino Acids

Nucleotide Biosynthesis

Biosynthesis of Membrane Lipids and Steroids

The Integration of Metabolism

DNA Replication, repair, and Recombination

RNA Synthesis and Processing

Protein Synthesis

The Control of Gene Expression in Prokaryotes

The Control of Gene Expression in Eukaryotes

Sensory Systems

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Molecular Motors

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How many ATP equivalents are produced from the total oxidation of one pyruvate to three CO₂?

For a single rotation of the Krebs cycle,are the acetyl carbons that enter the citric acid cycle the exact same carbons that leave as CO₂? Briefly explain.