$$\text{Glycogen}_{(n)} + \text{Pi} \rightarrow \text{Glycogen}_{(n-1)} + \text{Glucose-1-phosphate}$$

Question 1

Which of the following best explains why cancer cells often show increased glucose uptake and favor fermentation, as seen in PET scans?

Accepted Answer

Cancer cells use fermentation to rapidly regenerate NAD+ and support high rates of glycolysis, even in the presence of oxygen.

Question 2

During lactate fermentation, which of the following reactions occurs to regenerate NAD+ for glycolysis?

Accepted Answer

Pyruvate is reduced to lactate by lactate dehydrogenase, oxidizing NADH to NAD+.

Question 3

Which equation correctly represents the phosphorolysis reaction catalyzed by glycogen phosphorylase?

Accepted Answer

$$	ext{Glycogen}_{(n)} + 	ext{Pi} ightarrow 	ext{Glycogen}_{(n-1)} + 	ext{Glucose-1-phosphate}$$

Question 4

Which of the following is NOT a substrate that can enter glycolysis?

Accepted Answer

Acetyl-CoA

Question 5

Why can't gluconeogenesis simply reverse all steps of glycolysis?

Accepted Answer

Some glycolytic steps are highly exergonic and irreversible, requiring unique enzymes in gluconeogenesis.

Question 6

Which of the following enzymes is unique to gluconeogenesis and not found in glycolysis?

Accepted Answer

Pyruvate carboxylase

Question 7

Which molecule acts as an allosteric inhibitor of glycolysis but stimulates gluconeogenesis?

Accepted Answer

Acetyl-CoA

Question 8

What is the main purpose of fermentation in cells?

Accepted Answer

To regenerate NAD+ for glycolysis to continue.

Question 9

Which of the following best describes the regulation of phosphofructokinase-2 (PFK-2)?

Accepted Answer

PFK-2 is active when unphosphorylated, converting F6P to F2,6BP and stimulating glycolysis.

Question 10

Which step in gluconeogenesis involves the hydrolysis of a phosphoester bond to release inorganic phosphate, without requiring ATP?

Accepted Answer

Conversion of fructose-1,6-bisphosphate (F16BP) to fructose-6-phosphate (F6P)

Question 11

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

Accepted Answer

Converting glucose-6-phosphate to free glucose during gluconeogenesis

Question 12

Which of the following statements about ATP's regulation of phosphofructokinase-1 (PFK-1) is correct?

Accepted Answer

High levels of ATP bind to the allosteric site of PFK-1, inhibiting glycolysis.

Question 13

Which of the following best describes the Cori cycle?

Accepted Answer

The conversion of lactate from skeletal muscle to pyruvate in the liver, followed by gluconeogenesis.

Question 14

Which of the following is a correct equation for the conversion of pyruvate to lactate during fermentation?

Accepted Answer

$$	ext{Pyruvate} + 	ext{NADH} + 	ext{H}^+ ightarrow 	ext{Lactate} + 	ext{NAD}^+$$

Question 15

Which of the following best explains why glycolysis and gluconeogenesis are spatially regulated in the body?

Accepted Answer

To prevent futile cycling and ensure efficient energy use, glycolysis occurs mainly in muscle cells while gluconeogenesis occurs in liver cells.

Question 16

Which of the following statements about the energy requirements of gluconeogenesis is correct?

Accepted Answer

Gluconeogenesis uses up 4 ATP and 2 GTP to synthesize glucose.

Question 17

Which of the following best describes the effect of fructose-2,6-bisphosphate (F2,6BP) on glycolysis and gluconeogenesis?

Accepted Answer

F2,6BP stimulates glycolysis and inhibits gluconeogenesis.

Question 18

Which of the following is a plausible reason why PET scans use radiolabeled glucose analogues to detect tumors?

Accepted Answer

Tumor cells have increased glucose uptake and metabolism, making them visible with radiolabeled glucose.

Glycolysis, Fermentation, and Gluconeogenesis: Pathways and Regulation

Study Guide - Practice Questions