Question 1

In the citric acid cycle, one __________ is produced by a substrate-level phosphorylation.

Accepted Answer

The answer of In the citric acid cycle, one __________...

Question 2

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 carbo

Question 3

Starting with oxaloacetate in the glyoxylate cycle, identify what molecules enter and exit the glyoxylate cycle.

Accepted Answer

The cycle begins with the condensation o

Question 4

The glyoxylate cycle enables plants to survive using only

Accepted Answer

A)  pyruvate. 
B)  acetate. 
C)  oxaloacetate. 
D)  lactate. 
E)  None of the answers is correct. 
A)  pyruvate. 
B)  acetate. 
C)  oxaloacetate. 
D)  lactate. 
E)  None of the answers is correct.

Question 5

How is succinate dehydrogenase unique when compared to the other enzymes in the citric acid cycle?

Accepted Answer

It is the only enzyme embedded

Question 6

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

Accepted Answer

During periods of biosynthesis, oxaloace

Question 7

Which of the following is toxic due to its ability to react with neighboring sulfhydryls of dihydrolipoyl groups, thus blocking their reoxidation to lipoamide?

Accepted Answer

A)  fluoroacetate 
B)  carbon monoxide 
C)  arsenite 
D)  rotenone 
E)  cyanide 
A)  fluoroacetate 
B)  carbon monoxide 
C)  arsenite 
D)  rotenone 
E)  cyanide

Question 8

Formation of citrate from acetyl CoA and oxaloacetate is a(n) _________ reaction.

Accepted Answer

A)  oxidation 
B)  reduction 
C)  condensation 
D)  ligation 
E)  None of the answers is correct. 
A)  oxidation 
B)  reduction 
C)  condensation 
D)  ligation 
E)  None of the answers is correct.

Question 9

Which of the following is the primary mode of regulation for the pyruvate dehydrogenase complex?

Accepted Answer

A)  feedback inhibition by citrate 
B)  feed-forward activation by glucose 
C)  allosteric activation by ATP and NADH 
D)  allosteric inhibition by ADP and CO2 
E)  inhibition by phosphorylation 
A)  feedback inhibition by citrate 
B)  feed-forward activation by glucose 
C)  allosteric activation by ATP and NADH 
D)  allosteric inhibition by ADP and CO2 
E)  inhibition by phosphorylation

Question 10

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 11

The ΔG˚′ =-21 kJ mol-1 for the reaction catalyzed by isocitrate dehydrogenase, yet the ΔG˚′ = +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 12

_______________ is a citric acid cycle enzyme that is also an example of an iron-sulfur protein.

Accepted Answer

Aconitase

Question 13

Which of the following enzymes are found in the glyoxylate cycle but not in the citric acid cycle?

Accepted Answer

A)  malate synthase and isocitrate dehydrogenase 
B)  glyoxylate synthase and malate synthase 
C)  isocitrate lyase and malate dehydrogenase 
D)  malate synthase and isocitrate lyase 
E)  succinyl CoA synthetase and glyoxylate synthase 
A)  malate synthase and isocitrate dehydrogenase 
B)  glyoxylate synthase and malate synthase 
C)  isocitrate lyase and malate dehydrogenase 
D)  malate synthase and isocitrate lyase 
E)  succinyl CoA synthetase and glyoxylate synthase

Question 14

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

Accepted Answer

acetyl CoA

Question 15

Where in the cell is succinate dehydrogenase located?

Accepted Answer

A)  inner mitochondrial membrane 
B)  outer mitochondrial membrane 
C)  mitochondrial matrix 
D)  intermembrane space 
E)  cytosol 
A)  inner mitochondrial membrane 
B)  outer mitochondrial membrane 
C)  mitochondrial matrix 
D)  intermembrane space 
E)  cytosol

Question 16

Carbons from carbohydrates enter the citric acid cycle in the form of _______________.

Accepted Answer

The answer of Carbons from carbohydrates enter the citric acid...

Question 17

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 18

What enzyme(s) is (are) responsible for the following reaction? 
Pyruvate + CoA + NAD+ $\rightarrow$ acetyl CoA + NADH + H+ + CO2

Accepted Answer

A)  acetyl CoA synthetase 
B)  pyruvate decarboxylase 
C)  pyruvate dehydrogenase complex 
D)  pyruvate carboxylase 
E)  None of the answers is correct. 
A)  acetyl CoA synthetase 
B)  pyruvate decarboxylase 
C)  pyruvate dehydrogenase complex 
D)  pyruvate carboxylase 
E)  None of the answers is correct.

Question 19

The ____________ cycle is a process by which plants and some bacteria can convert two-carbon acetyl units into four-carbon units (succinate) for glucose synthesis, energy production, and biosynthesis.

Accepted Answer

The answer of The ____________ cycle is a process by...

Question 20

What is the energy source that drives the condensation of oxaloacetate and acetyl CoA to produce citrate?

Accepted Answer

Citrate synthase catalyzes the condensat

Exam 17: The Citric Acid Cycle

In the citric acid cycle, one __________ is produced by a substrate-level phosphorylation.

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.

Starting with oxaloacetate in the glyoxylate cycle, identify what molecules enter and exit the glyoxylate cycle.

The glyoxylate cycle enables plants to survive using only

How is succinate dehydrogenase unique when compared to the other enzymes in the citric acid cycle?

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

Which of the following is toxic due to its ability to react with neighboring sulfhydryls of dihydrolipoyl groups, thus blocking their reoxidation to lipoamide?

Formation of citrate from acetyl CoA and oxaloacetate is a(n) _________ reaction.

Which of the following is the primary mode of regulation for the pyruvate dehydrogenase complex?

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

_______________ is a citric acid cycle enzyme that is also an example of an iron-sulfur protein.

Which of the following enzymes are found in the glyoxylate cycle but not in the citric acid cycle?

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

Where in the cell is succinate dehydrogenase located?

Carbons from carbohydrates enter the citric acid cycle in the form of _______________.

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

What enzyme(s) is (are) responsible for the following reaction? Pyruvate + CoA + NAD+ →\rightarrow→ acetyl CoA + NADH + H+ + CO2

The ____________ cycle is a process by which plants and some bacteria can convert two-carbon acetyl units into four-carbon units (succinate) for glucose synthesis, energy production, and biosynthesis.

What is the energy source that drives the condensation of oxaloacetate and acetyl CoA to produce citrate?

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

Oxidative Phosphorylation

Catalytic Strategies

Regulatory Strategies

Carbohydrates

Lipids and Cell Membranes

Membrane Channels and Pumps

Signal-Transduction Pathways

Metabolism: Basic Concepts and Design

Glycolysis and Gluconeogenesis

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

The Immune System

Molecular Motors

Drug Development

Filters

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 enzyme(s) is (are) responsible for the following reaction? Pyruvate + CoA + NAD⁺ $\rightarrow$ acetyl CoA + NADH + H⁺ + CO₂