Q: What is the net reaction for gluconeogenesis from pyruvate to glucose?

$$2\ \text{pyruvate} + 2\ \text{NADH} + 4\ \text{ATP} + 2\ \text{GTP} + 6\ \text{H}_2\text{O} + 2\ \text{H}^+ \rightarrow \text{Glc} + 2\ \text{NAD}^+ + 4\ \text{ADP} + 2\ \text{GDP} + 6\ \text{P}_i$$

Question 1

Which of the following statements best describes the main purpose of gluconeogenesis in the liver?

Accepted Answer

To synthesize glucose from non-carbohydrate precursors to maintain blood glucose levels during fasting.

Question 2

Which of the following is NOT a substrate that can be used for gluconeogenesis in mammals?

Accepted Answer

Acetyl-CoA

Question 3

What is the net reaction for gluconeogenesis from pyruvate to glucose?

Accepted Answer

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

Question 4

Which enzyme catalyzes the conversion of pyruvate to oxaloacetate in gluconeogenesis, and what molecule activates this enzyme?

Accepted Answer

Pyruvate carboxylase; activated by acetyl-CoA

Question 5

Which hormone increases the transcription of the PEPCK gene, thereby stimulating gluconeogenesis?

Accepted Answer

Glucagon

Question 6

Fructose-1,6-bisphosphatase is inhibited by which of the following molecules?

Accepted Answer

AMP and Frc-2,6-bisPO4

Question 7

Why is the hydrolysis of glucose-6-phosphate to glucose considered metabolically irreversible?

Accepted Answer

It has a large negative $$\Delta G$$ due to the hydrolysis of a phosphate ester bond.

Question 8

Which transporter is responsible for moving glucose-6-phosphate into the endoplasmic reticulum for hydrolysis in the liver?

Accepted Answer

GLUT 7

Question 9

Glycerol, derived from triglyceride breakdown, enters gluconeogenesis after conversion to which intermediate?

Accepted Answer

Dihydroxyacetone phosphate

Question 10

In the Cori cycle, what is the primary fate of lactate produced in muscle cells during anaerobic glycolysis?

Accepted Answer

It is transported to the liver, where it is converted back to glucose via gluconeogenesis.

Question 11

Which of the following best describes the glucose-alanine cycle?

Accepted Answer

Alanine is released from muscle, transported to the liver, converted to glucose, and sent back to muscle.

Question 12

Which of the following steps in gluconeogenesis is regulated by the concentration of intermediates such as alanine or lactate?

Accepted Answer

The overall rate of gluconeogenesis increases with higher concentrations of alanine or lactate.

Question 13

Which of the following is a correct statement about the energy requirements of gluconeogenesis?

Accepted Answer

Gluconeogenesis is energetically costly, requiring both ATP and GTP to convert pyruvate to glucose.

Question 14

Which enzyme is responsible for the hydrolysis of fructose-1,6-bisphosphate to fructose-6-phosphate in gluconeogenesis?

Accepted Answer

Fructose-1,6-bisphosphatase

Question 15

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

Accepted Answer

To prevent futile cycling and ensure efficient use of energy resources.

Question 16

Which molecule is produced by PFK II when glucose concentration is high and acts as a key regulator of glycolysis and gluconeogenesis?

Accepted Answer

Fructose-2,6-bisphosphate

Question 17

A patient with a deficiency in glucose-6-phosphatase would most likely present with which of the following symptoms?

Accepted Answer

Inability to release free glucose from the liver, leading to hypoglycemia during fasting.

Question 18

Which of the following best describes the role of fatty acid oxidation in the Cori cycle?

Accepted Answer

It provides the ATP required for gluconeogenesis in the liver.

Question 19

Which of the following is a key difference between the Cori cycle and the glucose-alanine cycle?

Accepted Answer

The Cori cycle transports lactate from muscle to liver, while the glucose-alanine cycle transports alanine.

Gluconeogenesis: Pathways, Regulation, and Physiological Cycles

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