$\text{Oxaloacetate} + \text{GTP} \rightarrow \text{PEP} + \text{GDP} + \text{CO}_2$

$\text{Glucose 6-phosphate} \rightarrow \text{Glucose} + \text{Pi}$

$\text{Pyruvate} \rightarrow \text{Oxaloacetate} \rightarrow \text{PEP}$

Question 1

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

Accepted Answer

Pyruvate carboxylase; ATP

Question 2

What is the overall reaction catalyzed by PEP carboxykinase (PEPCK) in gluconeogenesis?

Accepted Answer

$	ext{Oxaloacetate} + 	ext{GTP} ightarrow 	ext{PEP} + 	ext{GDP} + 	ext{CO}_2$

Question 3

Which step in gluconeogenesis directly reverses the action of phosphofructokinase-1 (PFK-1) in glycolysis?

Accepted Answer

Fructose 1,6-bisphosphatase converting fructose 1,6-bisphosphate to fructose 6-phosphate

Question 4

Why is it necessary to convert pyruvate to oxaloacetate before forming phosphoenolpyruvate (PEP) in gluconeogenesis?

Accepted Answer

The direct reversal of pyruvate kinase is energetically unfavorable

Question 5

Which of the following best describes the role of glucose 6-phosphatase in gluconeogenesis?

Accepted Answer

It removes a phosphate group from glucose 6-phosphate to produce free glucose

Question 6

A patient has a deficiency in PEP carboxykinase. Which metabolic consequence would you expect?

Accepted Answer

Impaired ability to synthesize glucose from non-carbohydrate sources

Question 7

Which of the following reactions is unique to gluconeogenesis and does NOT occur in glycolysis?

Accepted Answer

$	ext{Glucose 6-phosphate} ightarrow 	ext{Glucose} + 	ext{Pi}$

Question 8

Which enzyme is present only in the liver and kidney, allowing these organs to release free glucose into the bloodstream?

Accepted Answer

Glucose 6-phosphatase

Question 9

If a mutation rendered fructose 1,6-bisphosphatase nonfunctional, which of the following would be a likely metabolic effect?

Accepted Answer

Accumulation of fructose 1,6-bisphosphate and impaired gluconeogenesis

Question 10

Which of the following best explains why gluconeogenesis is not simply the reverse of glycolysis?

Accepted Answer

Several glycolytic steps are highly exergonic and must be bypassed by different enzymes in gluconeogenesis

Question 11

Which of the following is a correct sequence of reactions in gluconeogenesis starting from pyruvate?

Accepted Answer

$	ext{Pyruvate} ightarrow 	ext{Oxaloacetate} ightarrow 	ext{PEP}$

Question 12

Which molecule is both a substrate in gluconeogenesis and an intermediate in the citric acid cycle?

Accepted Answer

Oxaloacetate

Question 13

A drug that inhibits glucose 6-phosphatase would most likely cause which of the following?

Accepted Answer

Inability to release free glucose from the liver during fasting

Question 14

Which of the following best describes the energy requirements for the conversion of pyruvate to phosphoenolpyruvate (PEP) in gluconeogenesis?

Accepted Answer

It requires both ATP and GTP

Question 15

Which enzyme catalyzes the hydrolysis of fructose 1,6-bisphosphate to fructose 6-phosphate?

Accepted Answer

Fructose 1,6-bisphosphatase

Gluconeogenesis: Key Steps and Enzymatic Reactions

Study Guide - Practice Questions