Question 1

Draw the citric acid cycle from isocitrate to fumarate only,showing and naming each intermediate.Show where high-energy phosphate compounds or reduced electron carriers are produced or consumed,and name the enzyme that catalyzes each step.

Accepted Answer

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Question 2

The reaction of the citric acid cycle that produces an ATP equivalent (in the form of GTP)by substrate level phosphorylation is the conversion of:

Accepted Answer

A) citrate to isocitrate. 
B) fumarate to malate. 
C) malate to oxaloacetate. 
D) succinate to fumarate. 
E) succinyl-CoA to succinate.

Question 3

Germinating plant seeds can convert stored fatty acids into oxaloacetate and a variety of carbohydrates.Animals cannot synthesize significant quantities of oxaloacetate or glucose from fatty acids.What accounts for this difference?

Accepted Answer

The answer of Germinating plant seeds can convert stored fatty...

Question 4

In the citric acid cycle,a five-carbon compound is decarboxylated to yield an activated four-carbon compound.Show the substrate and product in this step,and indicate where any cofactor(s)participate(s).

Accepted Answer

The answer of In the citric acid cycle,a five-carbon compound...

Question 5

Explain in quantitative terms the circumstances under which the following reaction can proceed. L-Malate + NAD⁺$\rightarrow$ oxaloacetate + NADH + H⁺ $\Delta$G'° = +29.7 kJ/mol

Accepted Answer

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Question 6

Show the structures of the reactants and products for two of the four redox reactions in the citric acid cycle.Indicate where any cofactors participate,and label the reactants,products,and cofactors as oxidants or reductants in the reaction.

Accepted Answer

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Question 7

Which of the following is not true of the reaction catalyzed by the pyruvate dehydrogenase complex?

Accepted Answer

A) Biotin participates in the decarboxylation. 
B) Both NAD+ and a flavin nucleotide act as electron carriers. 
C) The reaction occurs in the mitochondrial matrix. 
D) The substrate is held by the lipoyl-lysine "swinging arm." 
E) Two different cofactors containing -SH groups participate.

Question 8

During the reaction of pyruvate carboxylase,CO2 is covalently attached to all the following except:

Accepted Answer

A) phosphate. 
B) biotin. 
C) pyruvate. 
D) lysine. 
E) All of the above

Question 9

The human disease beriberi is caused by a deficiency of thiamine in the diet.People with severe beriberi have higher than normal levels of pyruvate in their blood and urine.Explain this observation in terms of specific enzymatic reaction(s).

Accepted Answer

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Question 10

Show the steps of the citric acid cycle from succinyl-CoA to oxaloacetate only.For each step,show structures of substrate and product,name the enzyme responsible,and show where cofactors participate.

Accepted Answer

The answer of Show the steps of the citric acid...

Question 11

Which combination of cofactors is involved in the conversion of pyruvate to acetyl-CoA?

Accepted Answer

A) Biotin,FAD,and TPP 
B) Biotin,NAD+,and FAD 
C) NAD+,biotin,and TPP 
D) Pyridoxal phosphate,FAD,and lipoic acid 
E) TPP,lipoic acid,and NAD+

Question 12

Which of the following is not true of the citric acid cycle?

Accepted Answer

A) All enzymes of the cycle are located in the cytoplasm,except succinate dehydrogenase,which is bound to the inner mitochondrial membrane. 
B) In the presence of malonate,one would expect succinate to accumulate. 
C) Oxaloacetate is used as a substrate but is not consumed in the cycle. 
D) Succinate dehydrogenase channels electrons directly into the electron transfer chain. 
E) The condensing enzyme is subject to allosteric regulation by ATP and NADH.

Question 13

The conversion of 1 mol of pyruvate to 3 mol of CO2 via pyruvate dehydrogenase and the citric acid cycle also yields _____ mol of NADH,_____ mol of FADH2,and _____ mol of ATP (or GTP).

Accepted Answer

A) 2;2;2 
B) 3;1;1 
C) 3;2;0 
D) 4;1;1 
E) 4;2;1

Question 14

Show the reactions by which $\alpha$-ketoglutarate is converted to malate in the citric acid cycle.

Accepted Answer

The answer of Show the reactions by which $\alpha$-ketoglutarate is...

Question 15

The standard reduction potentials (E'°)for the following half reactions are given. Fumarate + 2H+ + 2e- $\rightarrow$   succinate E'° = +0.031 V
FAD + 2H+ + 2e- $\rightarrow$   FADH2 E'° = -0.219 V
If succinate,fumarate,FAD,and FADH2,all at l M concentrations,were mixed together in the presence of succinate dehydrogenase,which of the following would happen initially?

Accepted Answer

A) Fumarate and succinate would become oxidized;FAD and FADH2 would become reduced. 
B) Fumarate would become reduced;FADH2 would become oxidized. 
C) No reaction would occur because all reactants and products are already at their standard concentrations. 
D) Succinate would become oxidized;FAD would become reduced. 
E) Succinate would become oxidized;FADH2 would be unchanged because it is a cofactor,not a substrate.

Question 16

Show the three reactions in the citric acid cycle in which NADH is produced,including the structures.None of these reactions involves molecular oxygen (O₂),but all three reactions are strongly inhibited by anaerobic conditions;explain why.

Accepted Answer

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Question 17

You are in charge of genetically engineering a new bacterium that will derive all of its ATP from sunlight by photosynthesis.Will you put the enzymes of the citric acid cycle in this organism? Briefly explain why or why not.

Accepted Answer

The answer of You are in charge of genetically engineering...

Question 18

Show the steps of the citric acid cycle in which a six-carbon compound is converted into the first four-carbon intermediate in the path.For each step,show structures of substrate and product,name the enzyme responsible,and show where cofactors participate.

Accepted Answer

The answer of Show the steps of the citric acid...

Exam 16: The Citric Acid Cycle

Draw the citric acid cycle from isocitrate to fumarate only,showing and naming each intermediate.Show where high-energy phosphate compounds or reduced electron carriers are produced or consumed,and name the enzyme that catalyzes each step.

The reaction of the citric acid cycle that produces an ATP equivalent (in the form of GTP) by substrate level phosphorylation is the conversion of:

Germinating plant seeds can convert stored fatty acids into oxaloacetate and a variety of carbohydrates.Animals cannot synthesize significant quantities of oxaloacetate or glucose from fatty acids.What accounts for this difference?

In the citric acid cycle,a five-carbon compound is decarboxylated to yield an activated four-carbon compound.Show the substrate and product in this step,and indicate where any cofactor(s)participate(s).

Explain in quantitative terms the circumstances under which the following reaction can proceed. L-Malate + NAD⁺ $\rightarrow$ oxaloacetate + NADH + H⁺ $\Delta$ G'° = +29.7 kJ/mol

Show the structures of the reactants and products for two of the four redox reactions in the citric acid cycle.Indicate where any cofactors participate,and label the reactants,products,and cofactors as oxidants or reductants in the reaction.

Which of the following is not true of the reaction catalyzed by the pyruvate dehydrogenase complex?

During the reaction of pyruvate carboxylase,CO₂ is covalently attached to all the following except:

The human disease beriberi is caused by a deficiency of thiamine in the diet.People with severe beriberi have higher than normal levels of pyruvate in their blood and urine.Explain this observation in terms of specific enzymatic reaction(s).

Show the steps of the citric acid cycle from succinyl-CoA to oxaloacetate only.For each step,show structures of substrate and product,name the enzyme responsible,and show where cofactors participate.

Which combination of cofactors is involved in the conversion of pyruvate to acetyl-CoA?

Which of the following is not true of the citric acid cycle?

The conversion of 1 mol of pyruvate to 3 mol of CO₂ via pyruvate dehydrogenase and the citric acid cycle also yields ___ mol of NADH,_ mol of FADH₂,and ___ mol of ATP (or GTP) .

Show the reactions by which $\alpha$ -ketoglutarate is converted to malate in the citric acid cycle.

Show the three reactions in the citric acid cycle in which NADH is produced,including the structures.None of these reactions involves molecular oxygen (O₂),but all three reactions are strongly inhibited by anaerobic conditions;explain why.

You are in charge of genetically engineering a new bacterium that will derive all of its ATP from sunlight by photosynthesis.Will you put the enzymes of the citric acid cycle in this organism? Briefly explain why or why not.

Show the steps of the citric acid cycle in which a six-carbon compound is converted into the first four-carbon intermediate in the path.For each step,show structures of substrate and product,name the enzyme responsible,and show where cofactors participate.

Exam 16: The Citric Acid Cycle

Draw the citric acid cycle from isocitrate to fumarate only,showing and naming each intermediate.Show where high-energy phosphate compounds or reduced electron carriers are produced or consumed,and name the enzyme that catalyzes each step.

The reaction of the citric acid cycle that produces an ATP equivalent (in the form of GTP) by substrate level phosphorylation is the conversion of:

Germinating plant seeds can convert stored fatty acids into oxaloacetate and a variety of carbohydrates.Animals cannot synthesize significant quantities of oxaloacetate or glucose from fatty acids.What accounts for this difference?

In the citric acid cycle,a five-carbon compound is decarboxylated to yield an activated four-carbon compound.Show the substrate and product in this step,and indicate where any cofactor(s)participate(s).

Explain in quantitative terms the circumstances under which the following reaction can proceed. L-Malate + NAD+ →\rightarrow→ oxaloacetate + NADH + H+ Δ\DeltaΔ G'° = +29.7 kJ/mol

Show the structures of the reactants and products for two of the four redox reactions in the citric acid cycle.Indicate where any cofactors participate,and label the reactants,products,and cofactors as oxidants or reductants in the reaction.

Which of the following is not true of the reaction catalyzed by the pyruvate dehydrogenase complex?

During the reaction of pyruvate carboxylase,CO2 is covalently attached to all the following except:

The human disease beriberi is caused by a deficiency of thiamine in the diet.People with severe beriberi have higher than normal levels of pyruvate in their blood and urine.Explain this observation in terms of specific enzymatic reaction(s).

Show the steps of the citric acid cycle from succinyl-CoA to oxaloacetate only.For each step,show structures of substrate and product,name the enzyme responsible,and show where cofactors participate.

Which combination of cofactors is involved in the conversion of pyruvate to acetyl-CoA?

Which of the following is not true of the citric acid cycle?

The conversion of 1 mol of pyruvate to 3 mol of CO2 via pyruvate dehydrogenase and the citric acid cycle also yields _____ mol of NADH,_____ mol of FADH2,and _____ mol of ATP (or GTP) .

Show the reactions by which α\alphaα -ketoglutarate is converted to malate in the citric acid cycle.

Show the three reactions in the citric acid cycle in which NADH is produced,including the structures.None of these reactions involves molecular oxygen (O2),but all three reactions are strongly inhibited by anaerobic conditions;explain why.

You are in charge of genetically engineering a new bacterium that will derive all of its ATP from sunlight by photosynthesis.Will you put the enzymes of the citric acid cycle in this organism? Briefly explain why or why not.

Show the steps of the citric acid cycle in which a six-carbon compound is converted into the first four-carbon intermediate in the path.For each step,show structures of substrate and product,name the enzyme responsible,and show where cofactors participate.

Explain in quantitative terms the circumstances under which the following reaction can proceed. L-Malate + NAD⁺ $\rightarrow$ oxaloacetate + NADH + H⁺ $\Delta$ G'° = +29.7 kJ/mol

During the reaction of pyruvate carboxylase,CO₂ is covalently attached to all the following except:

The conversion of 1 mol of pyruvate to 3 mol of CO₂ via pyruvate dehydrogenase and the citric acid cycle also yields ___ mol of NADH,_ mol of FADH₂,and ___ mol of ATP (or GTP) .

Show the reactions by which $\alpha$ -ketoglutarate is converted to malate in the citric acid cycle.

Show the three reactions in the citric acid cycle in which NADH is produced,including the structures.None of these reactions involves molecular oxygen (O₂),but all three reactions are strongly inhibited by anaerobic conditions;explain why.