Q: What is the overall free energy change ($\Delta G^\circ'$) for the net reaction of gluconeogenesis from pyruvate to glucose?

$\Delta G^\circ' = -37 \text{ kJ/mol}$

Question 1

Which enzyme catalyzes the conversion of pyruvate to oxaloacetate in the first step of gluconeogenesis, and what cofactor is required for its activity?

Accepted Answer

Pyruvate carboxylase; requires biotin as a cofactor

Question 2

Which of the following best describes the role of the Cori cycle during vigorous exercise?

Accepted Answer

It allows lactate produced in muscles to be transported to the liver, where it is converted back to glucose.

Question 3

Which of the following reactions in gluconeogenesis bypasses an irreversible step of glycolysis and is highly regulated?

Accepted Answer

Conversion of fructose-1,6-bisphosphate to fructose-6-phosphate by fructose-1,6-bisphosphatase

Question 4

What is the overall free energy change ($\Delta G^\circ'$) for the net reaction of gluconeogenesis from pyruvate to glucose?

Accepted Answer

$\Delta G^\circ' = -37 	ext{ kJ/mol}$

Question 5

Which molecule acts as an allosteric activator of pyruvate carboxylase, signaling the need for gluconeogenesis?

Accepted Answer

Acetyl-CoA

Question 6

In gluconeogenesis, which enzyme catalyzes the conversion of oxaloacetate to phosphoenolpyruvate (PEP), and what is the required energy source?

Accepted Answer

PEP carboxykinase; uses GTP as the energy source

Question 7

Which of the following best explains why gluconeogenesis and glycolysis are reciprocally regulated?

Accepted Answer

To prevent a futile cycle that would waste ATP and GTP without net production of glucose or pyruvate

Question 8

Which of the following is a substrate-level control mechanism in gluconeogenesis?

Accepted Answer

The $K_m$ of glucose-6-phosphatase for glucose-6-phosphate is much higher than the cellular concentration of glucose-6-phosphate

Question 9

Which of the following statements about the regulation of fructose-1,6-bisphosphatase is correct?

Accepted Answer

AMP acts as an allosteric inhibitor of fructose-1,6-bisphosphatase

Question 10

A patient with a deficiency in biotin would most likely have impaired activity of which gluconeogenic enzyme?

Accepted Answer

Pyruvate carboxylase

Question 11

Which of the following best describes the compartmentalization of pyruvate carboxylase and PEP carboxykinase in gluconeogenesis?

Accepted Answer

Pyruvate carboxylase is found only in the mitochondria, while PEP carboxykinase is found in both the mitochondria and cytosol

Question 12

Which of the following reactions is energetically favorable and irreversible in gluconeogenesis?

Accepted Answer

Hydrolysis of fructose-1,6-bisphosphate to fructose-6-phosphate

Question 13

Which of the following best explains the role of AMP in the regulation of gluconeogenesis?

Accepted Answer

AMP inhibits fructose-1,6-bisphosphatase, thereby downregulating gluconeogenesis

Question 14

Which of the following is the correct net reaction for gluconeogenesis from pyruvate?

Accepted Answer

$2	ext{Pyruvate} + 4	ext{ATP} + 2	ext{GTP} + 2	ext{NADH} + 4	ext{H}_2	ext{O} ightarrow 	ext{Glucose} + 4	ext{ADP} + 2	ext{GDP} + 6	ext{P}_i + 2	ext{NAD}^+ + 2	ext{H}^+$

Question 15

A mutation that decreases the affinity of fructose-1,6-bisphosphatase for AMP would most likely result in which of the following?

Accepted Answer

Increased gluconeogenesis even when cellular energy is low

Question 16

Which of the following best explains why erythrocytes rely exclusively on glycolysis for energy?

Accepted Answer

They lack mitochondria and cannot utilize oxidative phosphorylation

Question 17

Which of the following is a correct statement about the regulation of glycolysis and gluconeogenesis?

Accepted Answer

When one pathway is activated, the other is reciprocally inactivated to prevent wasteful cycling

Question 18

Which of the following enzymes is responsible for the hydrolysis of glucose-6-phosphate to free glucose in the final step of gluconeogenesis?

Accepted Answer

Glucose-6-phosphatase

Question 19

Which of the following best describes the effect of acetyl-CoA on pyruvate carboxylase?

Accepted Answer

Acetyl-CoA acts as an allosteric activator, increasing the enzyme's activity

Gluconeogenesis and Its Regulation: Biochemistry Study Notes

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