Exam 16: The Citric Acid Cycle

Two of the steps in the oxidative decarboxylation of pyruvate to acetyl-CoA do not involve the three carbons of pyruvate,yet are essential to the operation of the pyruvate dehydrogenase complex.Explain.

Free

(Essay)

4.8/5

(36)

Question 1

Correct Answer:

Verified

The two steps catalyzed by dihydrolipoyl dehydrogenase (E₃)are required to regenerate the oxidized form of lipoate,bound to dihydrolipoyl transacetylase,from the dihydrolipoyl (reduced)form produced in the oxidation of pyruvate.First,FAD is reduced to FADH₂ to reoxidize the dihydrolipoate,then NAD⁺ is reduced to NADH to reoxidize the FADH₂ to complete the reaction.

Suppose you found an overly high level of pyruvate in a patient's blood and urine.One possible cause is a genetic defect in the enzyme pyruvate dehydrogenase,but another plausible cause is a specific vitamin deficiency.Explain what vitamin might be deficient in the diet,and why that would account for high levels of pyruvate to be excreted in the urine.How would you determine which explanation is correct?

Free

(Essay)

4.9/5

(32)

Question 2

Correct Answer:

Verified

The most likely explanation is that the patient has a deficiency of thiamine,without which the cell cannot make thiamine pyrophosphate,the cofactor for pyruvate dehydrogenase.The inability to oxidize pyruvate produced by glycolysis to acetyl-CoA would lead to accumulation of pyruvate in blood and urine.The most direct test for this deficiency is to feed a diet supplemented with thiamine and determine whether urinary pyruvate levels fall.

What is the function of FAD in the pyruvate dehydrogenase complex? How is it regenerated?

Free

(Essay)

4.8/5

(38)

Question 3

Correct Answer:

Verified

FAD serves as the electron acceptor in the re-oxidation of the cofactor dihydrolipoate.It is converted to FADH₂ by this reaction and is regenerated by the passage of electrons to NAD⁺.

Anaplerotic reactions .

(Multiple Choice)

4.8/5

(25)

Question 4

For the following reaction, $\Delta$ G'° = 29.7 kJ/mol. L-Malate + NAD⁺ $\rightarrow$ oxaloacetate + NADH + H⁺ The reaction as written:

(Multiple Choice)

4.9/5

(41)

Question 5

All of the oxidative steps of the citric acid cycle are linked to the reduction of NAD⁺ except the reaction catalyzed by:

(Multiple Choice)

4.9/5

(34)

Question 6

The citric acid cycle is frequently described as the major pathway of aerobic catabolism,which means that it is an oxygen-dependent degradative process.However,none of the reactions of the cycle directly involves oxygen as a reactant.Why is the pathway oxygen-dependent?

(Essay)

4.8/5

(33)

Question 7

Which of the below is not required for the oxidative decarboxylation of pyruvate to form acetyl-CoA?

(Multiple Choice)

4.8/5

(37)

Question 8

In mammals,each of the following occurs during the citric acid cycle except:

(Multiple Choice)

4.8/5

(36)

Question 9

Match the cofactor with its function in the citric acid cycle.A given function may be used more than once or not at all. -

(Short Answer)

4.8/5

(40)

Question 10

In which reaction of the citric acid cycle does substrate-level phosphorylation occur?

(Essay)

4.9/5

(34)

Question 11

The glyoxylate cycle is:

(Multiple Choice)

4.8/5

(22)

Question 12

Briefly describe the relationship of the pyruvate dehydrogenase complex reaction to glycolysis and the citric acid cycle.

(Essay)

4.8/5

(29)

Question 13

A function of the glyoxylate cycle,in conjunction with the citric acid cycle,is to accomplish the:

(Multiple Choice)

4.7/5

(47)

Question 14

The reaction of the citric acid cycle that is most similar to the pyruvate dehydrogenase complex-catalyzed conversion of pyruvate to acetyl-CoA is the conversion of:

(Multiple Choice)

4.8/5

(33)

Question 15

The oxidative decarboxylation of $\alpha$ -ketoglutarate proceeds by means of multistep reactions in which all but one of the following cofactors are required.Which one is not required?

(Multiple Choice)

4.7/5

(30)

Question 16

At what point in the citric acid cycle do the methyl carbon from acetyl-CoA and the carbonyl carbon from oxaloacetate become chemically equivalent?

(Essay)

4.9/5

(25)

Question 17

Entry of acetyl-CoA into the citric acid cycle is decreased when:

(Multiple Choice)

4.8/5

(34)

Question 18

Malonate is a competitive inhibitor of succinate dehydrogenase.If malonate is added to a mitochondrial preparation that is oxidizing pyruvate as a substrate,which of the following compounds would you expect to decrease in concentration?

(Multiple Choice)

4.9/5

(32)

Question 19

Which of the following is not an intermediate of the citric acid cycle?

(Multiple Choice)

4.9/5

(28)

Question 20

Showing 1 - 20 of 58

Exam 16: The Citric Acid Cycle

Two of the steps in the oxidative decarboxylation of pyruvate to acetyl-CoA do not involve the three carbons of pyruvate,yet are essential to the operation of the pyruvate dehydrogenase complex.Explain.

What is the function of FAD in the pyruvate dehydrogenase complex? How is it regenerated?

Anaplerotic reactions .

For the following reaction, Δ\DeltaΔ G'° = 29.7 kJ/mol. L-Malate + NAD+ →\rightarrow→ oxaloacetate + NADH + H+ The reaction as written:

All of the oxidative steps of the citric acid cycle are linked to the reduction of NAD+ except the reaction catalyzed by:

The citric acid cycle is frequently described as the major pathway of aerobic catabolism,which means that it is an oxygen-dependent degradative process.However,none of the reactions of the cycle directly involves oxygen as a reactant.Why is the pathway oxygen-dependent?

Which of the below is not required for the oxidative decarboxylation of pyruvate to form acetyl-CoA?

In mammals,each of the following occurs during the citric acid cycle except:

Match the cofactor with its function in the citric acid cycle.A given function may be used more than once or not at all. -

In which reaction of the citric acid cycle does substrate-level phosphorylation occur?

The glyoxylate cycle is:

Briefly describe the relationship of the pyruvate dehydrogenase complex reaction to glycolysis and the citric acid cycle.

A function of the glyoxylate cycle,in conjunction with the citric acid cycle,is to accomplish the:

The reaction of the citric acid cycle that is most similar to the pyruvate dehydrogenase complex-catalyzed conversion of pyruvate to acetyl-CoA is the conversion of:

The oxidative decarboxylation of α\alphaα -ketoglutarate proceeds by means of multistep reactions in which all but one of the following cofactors are required.Which one is not required?

At what point in the citric acid cycle do the methyl carbon from acetyl-CoA and the carbonyl carbon from oxaloacetate become chemically equivalent?

Entry of acetyl-CoA into the citric acid cycle is decreased when:

Malonate is a competitive inhibitor of succinate dehydrogenase.If malonate is added to a mitochondrial preparation that is oxidizing pyruvate as a substrate,which of the following compounds would you expect to decrease in concentration?

Which of the following is not an intermediate of the citric acid cycle?

The Foundations of Biochemistry

Water

Amino Acids, peptides, and Proteins

The Three-Dimensional Structure of Proteins

Protein Function

Enzymes

Carbohydrates and Glycobiology

Nucleotides and Nucleic Acids

Recombinant Dna Technology

Lipids

Biological Membranes and Transport

Biosignaling

Principles of Bioenergetics

Glycolysis, gluconeogenesis, and the Pentose Phosphate Pathway

Principles of Metabolic Regulation

Fatty Acid Catabolism

Amino Acid Oxidation and the Production of Urea

Oxidative Phosphorylation and Photophosphorylation

Carbohydrate Biosynthesis in Plants and Bacteria

Lipid Biosynthesis

Biosynthesis of Amino Acids, nucleotides, and Related Molecules

Integration and Hormonal Regulation of Mammalian Metabolism

Genes and Chromosomes

Dna Metabolism

Rna Metabolism

Protein Metabolism

Regulation of Gene Expression

Filters

For the following reaction, $\Delta$ G'° = 29.7 kJ/mol. L-Malate + NAD⁺ $\rightarrow$ oxaloacetate + NADH + H⁺ The reaction as written:

All of the oxidative steps of the citric acid cycle are linked to the reduction of NAD⁺ except the reaction catalyzed by:

The oxidative decarboxylation of $\alpha$ -ketoglutarate proceeds by means of multistep reactions in which all but one of the following cofactors are required.Which one is not required?