$$\text{Fructose-6-phosphate} \rightarrow \text{Fructose-1,6-bisphosphate}$$

$$\text{Glucose} + 2 \text{ADP} + 2 \text{Pi} + 2 \text{NAD}^+ \rightarrow 2 \text{Pyruvate} + 2 \text{ATP} + 2 \text{NADH} + 2 \text{H}^+$$

Question 1

Which of the following statements best describes the role of Mg$$^{2+} in $$the hexokinase-catalyzed phosphorylation of glucose during glycolysis?

Accepted Answer

Mg$$^{2+}$$ shields the negative charges on ATP, making the γ-phosphorus atom more accessible for nucleophilic attack by glucose.

Question 2

Which enzyme catalyzes the committed and primary flux control step of glycolysis, and how is it regulated?

Accepted Answer

Phosphofructokinase-1 (PFK-1); inhibited by ATP and citrate, activated by AMP and ADP.

Question 3

What is the net ATP and NADH yield per molecule of glucose during glycolysis?

Accepted Answer

$$+2$$ ATP, $$+2$$ NADH

Question 4

In the absence of oxygen, what is the fate of pyruvate in human muscle cells, and which enzyme catalyzes this reaction?

Accepted Answer

Pyruvate is converted to lactate by lactate dehydrogenase.

Question 5

Which of the following best explains why gluconeogenesis requires more energy input than glycolysis yields?

Accepted Answer

Gluconeogenesis bypasses the irreversible steps of glycolysis using energetically costly reactions.

Question 6

Which of the following is a major gluconeogenic precursor in mammals?

Accepted Answer

Lactate

Question 7

A patient with a deficiency in glucose-6-phosphatase would have difficulty with which metabolic process?

Accepted Answer

Gluconeogenesis

Question 8

Which pathway is primarily responsible for generating NADPH and ribose 5-phosphate in cells?

Accepted Answer

Pentose phosphate pathway

Question 9

Which of the following reactions is catalyzed by phosphofructokinase-1 (PFK-1) in glycolysis?

Accepted Answer

$$	ext{Fructose-6-phosphate} ightarrow 	ext{Fructose-1,6-bisphosphate}$$

Question 10

Which of the following best describes the Cori cycle?

Accepted Answer

The recycling of lactate produced by muscles to glucose in the liver.

Question 11

Which enzyme is responsible for the conversion of pyruvate to acetyl-CoA under aerobic conditions?

Accepted Answer

Pyruvate dehydrogenase complex

Question 12

Which of the following statements about the regulation of glycolysis is correct?

Accepted Answer

Hexokinase is inhibited by excess glucose-6-phosphate.

Question 13

Which of the following is NOT a product of the pentose phosphate pathway?

Accepted Answer

FADH$$_2$$

Question 14

A red blood cell is placed in an anaerobic environment. Which of the following best describes its primary metabolic fate for glucose?

Accepted Answer

Glucose is converted to lactate via glycolysis and homolactic fermentation.

Question 15

Which of the following best explains why the reactions catalyzed by kinases in glycolysis are considered metabolically irreversible?

Accepted Answer

They have large negative $$\Delta G$$ values under cellular conditions.

Question 16

Which of the following is a correct equation for the overall glycolytic conversion of glucose to pyruvate?

Accepted Answer

$$	ext{Glucose} + 2 	ext{ADP} + 2 	ext{Pi} + 2 	ext{NAD}^+ ightarrow 2 	ext{Pyruvate} + 2 	ext{ATP} + 2 	ext{NADH} + 2 	ext{H}^+$$

Question 17

Which of the following best describes the fate of NADH produced during glycolysis under anaerobic conditions in yeast?

Accepted Answer

NADH is used to reduce acetaldehyde to ethanol.

Question 18

Which of the following statements about the pentose phosphate pathway is correct?

Accepted Answer

It is active in tissues that synthesize fatty acids or steroids.

Question 19

Which enzyme catalyzes the conversion of fructose 1,6-bisphosphate to dihydroxyacetone phosphate and glyceraldehyde 3-phosphate in glycolysis?

Accepted Answer

Aldolase

Glucose Metabolism: Glycolysis, Fermentation, Gluconeogenesis, and the Pentose Phosphate Pathway

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