Question 1

Conversion of 1 mol of acetyl-CoA to 2 mol of CO2 and CoA via the citric acid cycle results in the net production of:

Accepted Answer

A) 1 mol of citrate. 
B) 1 mol of FADH2. 
C) 1 mol of NADH. 
D) 1 mol of oxaloacetate. 
E) 7 mol of ATP. 
A) 1 mol of citrate. 
B) 1 mol of FADH2. 
C) 1 mol of NADH. 
D) 1 mol of oxaloacetate. 
E) 7 mol of ATP.

Question 2

Match the cofactors below with their roles in the pyruvate dehydrogenase complex reaction.
-

Accepted Answer

The answer of Match the cofactors below with their roles...

Question 3

In the citric acid cycle,a flavin coenzyme is required for:

Accepted Answer

A) condensation of acetyl-CoA and oxaloacetate. 
B) oxidation of fumarate. 
C) oxidation of isocitrate. 
D) oxidation of malate. 
E) oxidation of succinate. 
A) condensation of acetyl-CoA and oxaloacetate. 
B) oxidation of fumarate. 
C) oxidation of isocitrate. 
D) oxidation of malate. 
E) oxidation of succinate.

Question 4

The two moles of CO2 produced in the first turn of the citric acid cycle have their origin in the:

Accepted Answer

A) carboxyl and methylene carbons of oxaloacetate 
B) carboxyl group of acetate and a carboxyl group of oxaloacetate. 
C) carboxyl group of acetate and the keto group of oxaloacetate. 
D) two carbon atoms of acetate. 
E) two carboxyl groups derived from oxaloacetate. 
A) carboxyl and methylene carbons of oxaloacetate 
B) carboxyl group of acetate and a carboxyl group of oxaloacetate. 
C) carboxyl group of acetate and the keto group of oxaloacetate. 
D) two carbon atoms of acetate. 
E) two carboxyl groups derived from oxaloacetate.

Question 5

Explain why fluorocitrate,a potent inhibitor of the enzyme aconitase,is a deadly poison.

Accepted Answer

By inhibiting aconitase,fluorocitrate pr

Question 6

Which of the following cofactors is required for the conversion of succinate to fumarate in the citric acid cycle?

Accepted Answer

A) ATP 
B) Biotin 
C) FAD 
D) NAD+  
E) NADP+  
A) ATP 
B) Biotin 
C) FAD 
D) NAD+  
E) NADP+

Question 7

Intermediates in the citric acid cycle are used as precursors in the biosynthesis of:

Accepted Answer

A) amino acids. 
B) nucleotides. 
C) fatty acids. 
D) sterols. 
E) All of the above 
A) amino acids. 
B) nucleotides. 
C) fatty acids. 
D) sterols. 
E) All of the above

Question 8

There are few,if any,humans with defects in the enzymes of the citric acid cycle.Explain this observation in terms of the role of the citric acid cycle.

Accepted Answer

The citric acid cycle is central to all

Question 9

Citrate synthase and the NAD+-specific isocitrate dehydrogenase are two key regulatory enzymes of the citric acid cycle.These enzymes are inhibited by:

Accepted Answer

A) acetyl-CoA and fructose 6-phosphate. 
B) AMP and/or NAD+. 
C) AMP and/or NADH. 
D) ATP and/or NAD+. 
E) ATP and/or NADH. 
A) acetyl-CoA and fructose 6-phosphate. 
B) AMP and/or NAD+. 
C) AMP and/or NADH. 
D) ATP and/or NAD+. 
E) ATP and/or NADH.

Question 10

Which one of the following enzymatic activities would be decreased by thiamine deficiency?

Accepted Answer

A) Fumarase 
B) Isocitrate dehydrogenase 
C) Malate dehydrogenase 
D) Succinate dehydrogenase 
E) ($\alpha$-Ketoglutarate dehydrogenase complex) 
A) Fumarase 
B) Isocitrate dehydrogenase 
C) Malate dehydrogenase 
D) Succinate dehydrogenase 
E) ($\alpha$-Ketoglutarate dehydrogenase complex)

Question 11

Which of the following intermediates of the citric acid cycle is prochiral?

Accepted Answer

A) Citrate 
B) Isocitrate 
C) Malate 
D) Oxaloacetate 
E) Succinate 
A) Citrate 
B) Isocitrate 
C) Malate 
D) Oxaloacetate 
E) Succinate

Question 12

Glucose labeled with 14C in C-3 and C-4 is completely converted to acetyl-CoA via glycolysis and the pyruvate dehydrogenase complex.What percentage of the acetyl-CoA molecules formed will be labeled with 14C,and in which position of the acetyl moiety will the 14C label be found?

Accepted Answer

A) 100% of the acetyl-CoA will be labeled at C-1 (carboxyl). 
B) 100% of the acetyl-CoA will be labeled at C-2. 
C) 50% of the acetyl-CoA will be labeled,all at C-2 (methyl). 
D) No label will be found in the acetyl-CoA molecules. 
E) Not enough information is given to answer this question. 
A) 100% of the acetyl-CoA will be labeled at C-1 (carboxyl). 
B) 100% of the acetyl-CoA will be labeled at C-2. 
C) 50% of the acetyl-CoA will be labeled,all at C-2 (methyl). 
D) No label will be found in the acetyl-CoA molecules. 
E) Not enough information is given to answer this question.

Question 13

Preparation of an extract of muscle results in a dramatic decrease in the concentration of citric acid cycle intermediates compared to their concentrations in the tissue.However,in 1935,Szent-Gyorgi showed that the production of CO2 by the extract increased when succinate was added.In fact,for every mole of succinate added,many extra moles of CO2 were produced.Explain this effect in terms of the known catabolic pathways.

Accepted Answer

Succinate is an intermediate in the citr

Question 14

Which of the following statements about the oxidative decarboxylation of pyruvate in aerobic conditions in animal cells is correct?

Accepted Answer

A) One of the products of the reactions of the pyruvate dehydrogenase complex is a thioester of acetate. 
B) The methyl (-CH3)group is eliminated as CO2. 
C) The process occurs in the cytosolic compartment of the cell. 
D) The pyruvate dehydrogenase complex uses all of the following as cofactors: NAD+,lipoic acid,pyridoxal phosphate (PLP),and FAD. 
E) The reaction is so important to energy production that pyruvate dehydrogenase operates at full speed under all conditions. 
A) One of the products of the reactions of the pyruvate dehydrogenase complex is a thioester of acetate. 
B) The methyl (-CH3)group is eliminated as CO2. 
C) The process occurs in the cytosolic compartment of the cell. 
D) The pyruvate dehydrogenase complex uses all of the following as cofactors: NAD+,lipoic acid,pyridoxal phosphate (PLP),and FAD. 
E) The reaction is so important to energy production that pyruvate dehydrogenase operates at full speed under all conditions.

Question 15

The citric acid cycle begins with the condensation of acetyl-CoA with oxaloacetate.Describe three possible sources for the acetyl-CoA.

Accepted Answer

Acetyl-CoA is produced by (1)t

Question 16

Which one of the following is not associated with the oxidation of substrates by the citric acid cycle?

Accepted Answer

A) All of the below are involved. 
B) CO2 production 
C) Flavin reduction 
D) Lipoic acid present in some of the enzyme systems 
E) Pyridine nucleotide oxidation 
A) All of the below are involved. 
B) CO2 production 
C) Flavin reduction 
D) Lipoic acid present in some of the enzyme systems 
E) Pyridine nucleotide oxidation

Question 17

Acetyl-CoA labeled with 14C in both of its acetate carbon atoms is incubated with unlabeled oxaloacetate and a crude tissue preparation capable of carrying out the reactions of the citric acid cycle.After one turn of the cycle,oxaloacetate would have 14C in:

Accepted Answer

A) all four carbon atoms. 
B) no pattern that is predictable from the information provided. 
C) none of its carbon atoms. 
D) the keto carbon and one of the carboxyl carbons. 
E) the two carboxyl carbons. 
A) all four carbon atoms. 
B) no pattern that is predictable from the information provided. 
C) none of its carbon atoms. 
D) the keto carbon and one of the carboxyl carbons. 
E) the two carboxyl carbons.

Question 18

During seed germination,the glyoxylate pathway is important to plants because it enables them to:

Accepted Answer

A) carry out the net synthesis of glucose from acetyl-CoA. 
B) form acetyl-CoA from malate. 
C) get rid of isocitrate formed from the aconitase reaction. 
D) obtain glyoxylate for cholesterol biosynthesis. 
E) obtain glyoxylate for pyrimidine synthesis. 
A) carry out the net synthesis of glucose from acetyl-CoA. 
B) form acetyl-CoA from malate. 
C) get rid of isocitrate formed from the aconitase reaction. 
D) obtain glyoxylate for cholesterol biosynthesis. 
E) obtain glyoxylate for pyrimidine synthesis.

Question 19

Describe the enzymes,cofactors,intermediates,and products the pyruvate dehydrogenase complex.

Accepted Answer

The pyruvate dehydrogenase complex consi

Question 20

Oxaloacetate uniformly labeled with 14C (i.e. ,with equal amounts of 14C in each of its carbon atoms)is condensed with unlabeled acetyl-CoA.After a single pass through the citric acid cycle back to oxaloacetate,what fraction of the original radioactivity will be found in the oxaloacetate?

Accepted Answer

A) All 
B) 1/2 
C) 1/3 
D) 1/4 
E) 3/4 
A) All 
B) 1/2 
C) 1/3 
D) 1/4 
E) 3/4

Exam 16: The Citric Acid Cycle

Conversion of 1 mol of acetyl-CoA to 2 mol of CO2 and CoA via the citric acid cycle results in the net production of:

Match the cofactors below with their roles in the pyruvate dehydrogenase complex reaction. -

In the citric acid cycle,a flavin coenzyme is required for:

The two moles of CO2 produced in the first turn of the citric acid cycle have their origin in the:

Explain why fluorocitrate,a potent inhibitor of the enzyme aconitase,is a deadly poison.

Which of the following cofactors is required for the conversion of succinate to fumarate in the citric acid cycle?

Intermediates in the citric acid cycle are used as precursors in the biosynthesis of:

There are few,if any,humans with defects in the enzymes of the citric acid cycle.Explain this observation in terms of the role of the citric acid cycle.

Citrate synthase and the NAD+-specific isocitrate dehydrogenase are two key regulatory enzymes of the citric acid cycle.These enzymes are inhibited by:

Which one of the following enzymatic activities would be decreased by thiamine deficiency?

Which of the following intermediates of the citric acid cycle is prochiral?

Glucose labeled with 14C in C-3 and C-4 is completely converted to acetyl-CoA via glycolysis and the pyruvate dehydrogenase complex.What percentage of the acetyl-CoA molecules formed will be labeled with 14C,and in which position of the acetyl moiety will the 14C label be found?

Which of the following statements about the oxidative decarboxylation of pyruvate in aerobic conditions in animal cells is correct?

The citric acid cycle begins with the condensation of acetyl-CoA with oxaloacetate.Describe three possible sources for the acetyl-CoA.

Which one of the following is not associated with the oxidation of substrates by the citric acid cycle?

Acetyl-CoA labeled with 14C in both of its acetate carbon atoms is incubated with unlabeled oxaloacetate and a crude tissue preparation capable of carrying out the reactions of the citric acid cycle.After one turn of the cycle,oxaloacetate would have 14C in:

During seed germination,the glyoxylate pathway is important to plants because it enables them to:

Describe the enzymes,cofactors,intermediates,and products the pyruvate dehydrogenase complex.

Oxaloacetate uniformly labeled with 14C (i.e. ,with equal amounts of 14C in each of its carbon atoms)is condensed with unlabeled acetyl-CoA.After a single pass through the citric acid cycle back to oxaloacetate,what fraction of the original radioactivity will be found in the oxaloacetate?

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

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Conversion of 1 mol of acetyl-CoA to 2 mol of CO₂ and CoA via the citric acid cycle results in the net production of:

The two moles of CO₂ produced in the first turn of the citric acid cycle have their origin in the:

Citrate synthase and the NAD⁺-specific isocitrate dehydrogenase are two key regulatory enzymes of the citric acid cycle.These enzymes are inhibited by:

Glucose labeled with ¹⁴C in C-3 and C-4 is completely converted to acetyl-CoA via glycolysis and the pyruvate dehydrogenase complex.What percentage of the acetyl-CoA molecules formed will be labeled with ¹⁴C,and in which position of the acetyl moiety will the ¹⁴C label be found?

Acetyl-CoA labeled with ¹⁴C in both of its acetate carbon atoms is incubated with unlabeled oxaloacetate and a crude tissue preparation capable of carrying out the reactions of the citric acid cycle.After one turn of the cycle,oxaloacetate would have ¹⁴C in:

Oxaloacetate uniformly labeled with ¹⁴C (i.e. ,with equal amounts of ¹⁴C in each of its carbon atoms)is condensed with unlabeled acetyl-CoA.After a single pass through the citric acid cycle back to oxaloacetate,what fraction of the original radioactivity will be found in the oxaloacetate?