Ch14 Adaptive Quiz: Glycolysis, Gluconeogenesis, and the Pentose Phosphate Pathway

The glycolytic intermediate glyceraldehyde 3-phosphate loses a hydride ion during its conversion to 1,3-bisphosphoglycerate. Which compound accepts the lost hydride ion?

A) ADP

B) NAD⁺

C) NADH

D) ATP

B) NAD⁺

What type of reaction begins the chemical digestion of starch?

A) dehydration

B) hydrolysis

C) isomerization

D) dehydrogenation

E) phosphorolysis

B) hydrolysis

Thiamine pyrophosphate is a coenzyme derived from which vitamin?

A) vitamin B₁

B) vitamin C

C) vitamin B₆

D) vitamin B₁₂

A) vitamin B₁

What is the first regulatory enzyme in the gluconeogenic pathway?

A) hexokinase

B) phosphofructokinase-1

C) pyruvate kinase

D) pyruvate carboxylase

D) pyruvate carboxylase

How does acetyl-CoA affect the activity of pyruvate carboxylase and pyruvate dehydrogenase?

A) It activates pyruvate carboxylase but inhibits pyruvate dehydrogenase.

B) It activates both pyruvate carboxylase and pyruvate dehydrogenase.

C) It inhibits both pyruvate carboxylase and pyruvate dehydrogenase.

D) It activates pyruvate dehydrogenase but inhibits pyruvate carboxylase.

A) It activates pyruvate carboxylase but inhibits pyruvate dehydrogenase.

Which glycolytic enzyme ensures that pathway intermediates remain in the cell?

A) hexokinase

B) aldolase

C) phosphoglycerate kinase

D) enolase

E) pyruvate kinase

A) hexokinase

Why can cows digest cellulose whereas humans cannot?

A) The bovine stomach contains symbiotic microorganisms that produce cellulase, but the human stomach does not.

B) Cows eat their own feces after intestinal bacteria have digested the cellulose, but humans do not.

C) Bovine saliva contains cellulase, but human saliva does not.

D) The brush border of both humans and cows produces cellulase, but the human version of the enzyme is not functional.

A) The bovine stomach contains symbiotic microorganisms that produce cellulase, but the human stomach does not.

Which statement describes the Warburg effect?

A) Tumors carry out glycolysis at a much lower rate than normal tissue when oxygen is scarce.

B) Tumors carry out glycolysis at a much lower rate than normal tissue, even when oxygen is available.

C) Tumors carry out glycolysis at a much higher rate than normal tissue, even when oxygen is available.

D) Tumors carry out glycolysis at a much higher rate than normal tissue, but only when oxygen is scarce.

C) Tumors carry out glycolysis at a much higher rate than normal tissue, even when oxygen is available.

Which enzymes catalyze the three reactions of glycolysis that are essentially irreversible and cannot be used in gluconeogenesis?

A) phosphohexose isomerase, glyceraldehyde 3-phosphate dehydrogenase, pyruvate kinase

B) hexokinase, phosphofructokinase-1, pyruvate kinase

C) phosphohexose isomerase, phosphofructokinase-1, glyceraldehyde 3-phosphate dehydrogenase

D) phosphofructokinase-1, glyceraldehyde 3-phosphate dehydrogenase, pyruvate kinase

B) hexokinase, phosphofructokinase-1, pyruvate kinase

Which condition would increase the transcription of glucose 6-phosphatase?

A) low [ATP]

B) glucagon signaling

C) high [P_i]

D) high blood glucose level

B) glucagon signaling

Glycolysis can be thought of as two chemical processes: the conversion of glucose to pyruvate (ΔG′° = −146 kJ/mol) and the formation of ATP from ADP and P_i (ΔG′° = 61 kJ/mol). Based on these values, which statement is true about glycolysis overall?

A) Glycolysis is readily reversible, driven to completion by a small net decrease in free energy.

B) Glycolysis is essentially irreversible, driven to completion by a large net increase in free energy.

C) Glycolysis is readily reversible, driven to completion by a small net increase in free energy.

D) Glycolysis is essentially irreversible, driven to completion by a large net decrease in free energy.

D) Glycolysis is essentially irreversible, driven to completion by a large net decrease in free energy.

What is the net ATP yield of glycolysis starting with fructose in the liver?

A) 1 ATP

B) 2 ATP

C) 3 ATP

D) 4 ATP

B) 2 ATP

How does citrate modify the activity of phosphofructokinase-1 (PFK-1)?

A) by competing with fructose 6-phosphate at the active site

B) by blocking the inhibitory effect of ATP

C) by increasing the inhibitory effect of fructose 2,6-bisphosphate

D) by increasing the inhibitory effect of ATP

D) by increasing the inhibitory effect of ATP

Which of the 20 common amino acids does NOT furnish carbon for net glucose synthesis?

A) asparagine and aspartate

B) phenylalanine and tyrosine

C) glutamate and glutamine

D) leucine and lysine

D) leucine and lysine

Why does the gluconeogenic pathway bypass the reaction catalyzed by hexokinase?

A) Reversal of the hexokinase reaction would be energetically unfavorable.

B) Reversal of the hexokinase reaction would consume additional ATP.

C) Reversal of the hexokinase reaction would consume additional reducing equivalents.

D) Reversal of the hexokinase reaction would lower the cytosolic pH by releasing a proton.

A) Reversal of the hexokinase reaction would be energetically unfavorable.

Which statement does NOT describe a functional consequence of having phosphorylated intermediates in the glycolytic pathway?

A) Phosphorylation of the intermediates prevents them from leaving the cell.

B) The binding of phosphate groups to the active sites of enzymes lowers the activation energy and increases the specificity of the enzymatic reactions.

C) All phosphorylated intermediates in the glycolytic pathway form ATP by substrate-level phosphorylation.

D) Phosphoryl groups are essential components in the enzymatic conservation of metabolic energy.

C) All phosphorylated intermediates in the glycolytic pathway form ATP by substrate-level phosphorylation.

How would a deficiency in the liver isozyme of hexokinase affect the entry of glucose, fructose, and mannose into glycolysis in hepatocytes?

A) It would prevent the entry of all three sugars into glycolysis.

B) All three sugars would still be able to enter glycolysis.

C) It would prevent the entry of glucose and mannose, but not the entry of fructose into glycolysis.

D) It would prevent the entry of glucose, but not the entry of fructose and mannose into glycolysis.

C) It would prevent the entry of glucose and mannose, but not the entry of fructose into glycolysis.

Which enzyme in glycolysis forms a Schiff base intermediate in the course of catalyzing the reaction with which it is associated?

A) phosphofructokinase

B) hexokinase

C) glyceraldehyde 3-phosphate dehydrogenase

D) aldolase

E) phosphoglycerate mutase

D) aldolase

Although the standard free-energy change (ΔG′°) of the two-step path from pyruvate to phosphoenolpyruvate (PEP) is 0.9 kJ/mol, the actual free-energy change (ΔG), calculated from measured cellular concentrations of intermediates, is very strongly negative (−25 kJ/mol). What explains this difference between the standard and actual free-energy change?

A) The ready consumption of PEP in other reactions keeps its concentration relatively low.

B) The free-energy change of ATP hydrolysis in living cells is less negative than under standard conditions.

C) The starting concentrations of ATP and GTP are much higher in living cells than under standard conditions.

D) The ready conversion of pyruvate to acetyl-CoA keeps its concentration relatively low.

A) The ready consumption of PEP in other reactions keeps its concentration relatively low.