Q: Which of the following equations correctly represents the reaction catalyzed by glucose-6-phosphatase?

$$\text{Glucose-6-phosphate} + \text{H}_2\text{O} \rightarrow \text{glucose} + \text{P}_i$$

Q: Which of the following best describes the energy requirements for the synthesis of one molecule of glucose from two molecules of pyruvate via gluconeogenesis?

$$4 \text{ ATP}, 2 \text{ GTP}, 2 \text{ NADH}$$

Question 1

Which of the following tissues relies almost exclusively on glucose as its primary energy source under normal physiological conditions?

Accepted Answer

Central nervous system

Question 2

During prolonged fasting, which metabolic pathway is primarily responsible for maintaining blood glucose levels?

Accepted Answer

Gluconeogenesis

Question 3

Which enzyme catalyzes the conversion of pyruvate to oxaloacetate in gluconeogenesis, and what cofactor is required?

Accepted Answer

Pyruvate carboxylase; biotin

Question 4

Which of the following equations correctly represents the reaction catalyzed by glucose-6-phosphatase?

Accepted Answer

$$	ext{Glucose-6-phosphate} + 	ext{H}_2	ext{O} ightarrow 	ext{glucose} + 	ext{P}_i$$

Question 5

Which of the following statements about the regulation of glycolysis and gluconeogenesis in the liver is CORRECT?

Accepted Answer

Fructose 2,6-bisphosphate activates phosphofructokinase-1 (PFK-1) and inhibits fructose 1,6-bisphosphatase (FBPase-1).

Question 6

Which of the following is NOT a substrate for gluconeogenesis in humans?

Accepted Answer

Leucine

Question 7

Why can't muscle tissue contribute directly to blood glucose via gluconeogenesis?

Accepted Answer

Muscle lacks glucose-6-phosphatase.

Question 8

Which of the following best describes the energy requirements for the synthesis of one molecule of glucose from two molecules of pyruvate via gluconeogenesis?

Accepted Answer

$$4 	ext{ ATP}, 2 	ext{ GTP}, 2 	ext{ NADH}$$

Question 9

A patient with uncontrolled diabetes mellitus is found to have elevated hepatic gluconeogenesis. Which of the following best explains this finding?

Accepted Answer

Glucagon and cortisol promote gluconeogenesis during insulin deficiency.

Question 10

Which of the following steps in gluconeogenesis bypasses an irreversible step of glycolysis catalyzed by phosphofructokinase-1 (PFK-1)?

Accepted Answer

Fructose-1,6-bisphosphatase catalyzing the conversion of fructose-1,6-bisphosphate to fructose-6-phosphate

Question 11

Which of the following best describes the Cori cycle?

Accepted Answer

The conversion of lactate produced by anaerobic glycolysis in muscle to glucose in the liver

Question 12

Which of the following statements about the conversion of pyruvate to phosphoenolpyruvate (PEP) in gluconeogenesis is CORRECT?

Accepted Answer

It requires two enzymes: pyruvate carboxylase and PEP carboxykinase.

Question 13

Which of the following best explains why gluconeogenesis and glycolysis do not occur simultaneously at high rates in the same cell?

Accepted Answer

They are regulated in opposite directions by key allosteric effectors and hormones.

Question 14

Which of the following is a positive allosteric effector of pyruvate carboxylase?

Accepted Answer

Acetyl-CoA

Question 15

A patient is given a drug that inhibits the enzyme fructose-1,6-bisphosphatase. Which of the following would most likely occur as a result?

Accepted Answer

Decreased gluconeogenesis and hypoglycemia during fasting

Question 16

Which of the following best describes the role of magnesium ions (Mg$$^{2+}) in $$gluconeogenesis?

Accepted Answer

They act as essential cofactors for several enzymes, including glucose-6-phosphatase and PEP carboxykinase.

Question 17

Which of the following best explains why gluconeogenesis is considered an energetically expensive process?

Accepted Answer

It requires the hydrolysis of multiple high-energy phosphate bonds (ATP and GTP) per glucose synthesized.

Question 18

Which of the following statements about the regulation of gluconeogenesis by fructose 2,6-bisphosphate is CORRECT?

Accepted Answer

Fructose 2,6-bisphosphate inhibits fructose-1,6-bisphosphatase, decreasing gluconeogenesis.

Gluconeogenesis and Its Regulation: Biochemistry Study Guide

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