Question 1

Which enzyme catalyzes the committed step of glycolysis, and what is the significance of this step?

Accepted Answer

Phosphofructokinase-1 (PFK-1); it commits glucose to metabolism via glycolysis and is the primary regulatory point.

Question 2

What is the effect of high concentrations of ATP on phosphofructokinase-1 (PFK-1) activity, and why?

Accepted Answer

It decreases PFK-1 activity by binding to a regulatory site, signaling high energy status.

Question 3

Which molecule can reverse the inhibitory effect of ATP on PFK-1, and what is the mechanism?

Accepted Answer

AMP; it competes with ATP at the regulatory site and signals low energy status.

Question 4

Which of the following best describes the role of fructose-2,6-bisphosphate in glycolysis regulation?

Accepted Answer

It activates PFK-1 by increasing its affinity for fructose-6-phosphate and decreasing ATP inhibition.

Question 5

During glycolysis, which reaction is bypassed in the presence of arsenate, and what is the consequence for ATP yield?

Accepted Answer

The phosphoglycerate kinase reaction; no net ATP is produced from glycolysis.

Question 6

Which glycolytic enzyme catalyzes a reaction that is near equilibrium under physiological conditions and is not a major regulatory point?

Accepted Answer

Aldolase

Question 7

What is the net ATP yield from glycolysis of one molecule of glucose under anaerobic conditions?

Accepted Answer

2 ATP

Question 8

Which coenzyme is reduced during the oxidation of glyceraldehyde-3-phosphate in glycolysis?

Accepted Answer

NAD+

Question 9

In the conversion of 2-phosphoglycerate to phosphoenolpyruvate (PEP), what is the main purpose of this reaction in glycolysis?

Accepted Answer

To rearrange the molecule to a form with a higher phosphoryl transfer potential for ATP synthesis.

Question 10

Which of the following statements about the fate of pyruvate under anaerobic conditions in muscle is correct?

Accepted Answer

Pyruvate is reduced to lactate, regenerating NAD+ for glycolysis.

Question 11

Which vitamin is a precursor for the coenzyme NAD+ used in glycolysis?

Accepted Answer

Vitamin B3 (niacin)

Question 12

A patient is found to have a deficiency in triose phosphate isomerase. Which glycolytic intermediate would you expect to accumulate?

Accepted Answer

Dihydroxyacetone phosphate (DHAP)

Question 13

Which of the following best explains why glycolysis can proceed rapidly in erythrocytes despite several reactions having positive $$\Delta G^\circ'$$ values?

Accepted Answer

The actual $$\Delta G$$ values in the cell are near zero due to metabolite concentrations being far from equilibrium.

Question 14

Which glycolytic enzyme requires a phosphorylated histidine residue for its mechanism and is involved in the migration of a phosphate group within the substrate?

Accepted Answer

Phosphoglycerate mutase

Question 15

Which of the following is a direct product of the pyruvate kinase reaction in glycolysis?

Accepted Answer

Pyruvate

Question 16

In yeast, what is the primary purpose of converting pyruvate to ethanol during fermentation?

Accepted Answer

To regenerate NAD+ for continued glycolysis.

Question 17

Which of the following best describes the mechanism of action for class I aldolase in glycolysis?

Accepted Answer

It forms a Schiff base intermediate with an active site lysine.

Question 18

Which glycolytic intermediate is an important allosteric activator of pyruvate kinase?

Accepted Answer

Fructose-1,6-bisphosphate

Question 19

Which of the following statements about substrate-level phosphorylation in glycolysis is correct?

Accepted Answer

It involves the direct transfer of a phosphate group to ADP to form ATP.

Question 20

A patient is exposed to arsenate, which mimics phosphate in glycolysis. What is the most likely metabolic consequence?

Accepted Answer

No net ATP production from glycolysis due to bypass of the phosphoglycerate kinase step.

LEC 18 Glycolysis: Pathway, Regulation, and Metabolic Fate

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