Question 1

Which enzyme catalyzes the oxidation and phosphorylation of glyceraldehyde-3-phosphate in glycolysis, and what are the products of this reaction?

Accepted Answer

Glyceraldehyde-3-phosphate dehydrogenase; products are 1,3-bisphosphoglycerate and NADH

Question 2

During the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate, which type of phosphorylation occurs and what is the significance?

Accepted Answer

Substrate-level phosphorylation; it directly produces ATP

Question 3

What is the role of Mg$$^{2+} in $$the activity of phosphoglycerate mutase during glycolysis?

Accepted Answer

It stabilizes the negative charges on the phosphate group during the reaction

Question 4

Which reaction in glycolysis is responsible for the generation of the highest energy phosphate compound, and what is the compound?

Accepted Answer

Conversion of 2-phosphoglycerate to phosphoenolpyruvate by enolase; phosphoenolpyruvate

Question 5

What is the net ATP yield from one molecule of glucose during anaerobic glycolysis (lactic acid fermentation)?

Accepted Answer

$$2$$

Question 6

Which enzyme catalyzes the final step of glycolysis, and what is the reaction it performs?

Accepted Answer

Pyruvate kinase; transfer of a phosphate group from phosphoenolpyruvate to ADP to form pyruvate and ATP

Question 7

In alcoholic fermentation, which cofactor is essential for the decarboxylation of pyruvate to acetaldehyde?

Accepted Answer

Thiamine pyrophosphate (TPP)

Question 8

What is the overall chemical equation for glycolysis under anaerobic conditions (lactic acid fermentation)?

Accepted Answer

$$\mathrm{Glucose} + 2\,\mathrm{ADP} + 2\,\mathrm{Pi} \rightarrow 2\,\mathrm{Lactate} + 2\,\mathrm{ATP} + 2\,\mathrm{H}_2\mathrm{O}$$

Question 9

Which step in glycolysis involves the formation of a covalent enzyme-substrate intermediate, and what is the enzyme?

Accepted Answer

Glyceraldehyde-3-phosphate dehydrogenase; formation of thiohemiacetal intermediate

Question 10

What is the function of lactate dehydrogenase in muscle cells under anaerobic conditions?

Accepted Answer

It reduces pyruvate to lactate, regenerating NAD+

Question 11

Which of the following best explains why phosphoenolpyruvate (PEP) has a high phosphoryl transfer potential?

Accepted Answer

PEP is stabilized by resonance after phosphate transfer, making the reaction highly exergonic

Question 12

During glycolysis, which reaction is catalyzed by enolase and what is the product?

Accepted Answer

Conversion of 2-phosphoglycerate to phosphoenolpyruvate

Question 13

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

Accepted Answer

It directly transfers a phosphate group from a high-energy intermediate to ADP

Question 14

In alcoholic fermentation, what is the role of alcohol dehydrogenase (ADH)?

Accepted Answer

It reduces acetaldehyde to ethanol using NADH

Question 15

Which of the following best describes the efficiency of ATP production during lactic acid fermentation compared to aerobic respiration?

Accepted Answer

Lactic acid fermentation is less efficient, producing only about 31% of the energy available from glucose

Question 16

Which muscle fiber type relies primarily on glycolysis for rapid ATP production and is most active during sprinting?

Accepted Answer

Fast-twitch (white) fibers

Question 17

What is the fate of pyruvate under aerobic conditions in mammalian cells?

Accepted Answer

It is oxidized to acetyl-CoA and enters the citric acid cycle

Question 18

Which of the following is a key regulatory mechanism for pyruvate kinase in glycolysis?

Accepted Answer

Allosteric inhibition by ATP and activation by fructose-1,6-bisphosphate

Question 19

Which cofactor is required by pyruvate decarboxylase for the decarboxylation of pyruvate in alcoholic fermentation?

Accepted Answer

Thiamine pyrophosphate (TPP)

2nd Phase of Glycolysis and Pyruvate Fate: Mechanisms, Energetics, and Fermentation

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