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

Question 1

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

Accepted Answer

Some glycolytic reactions are highly exergonic and irreversible, requiring bypass reactions in gluconeogenesis.

Question 2

Which enzyme catalyzes the conversion of pyruvate to phosphoenolpyruvate (PEP) during gluconeogenesis, and what is the required cofactor?

Accepted Answer

Pyruvate carboxylase (with biotin) and PEP carboxykinase; ATP and GTP

Question 3

Which of the following molecules cannot serve as a substrate for gluconeogenesis in humans?

Accepted Answer

Even-chain fatty acids

Question 4

What is the net energy cost (in terms of ATP and GTP) for the synthesis of one glucose molecule from two pyruvate molecules during gluconeogenesis?

Accepted Answer

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

Question 5

Which enzyme is responsible for bypassing the irreversible step catalyzed by phosphofructokinase-1 (PFK-1) in glycolysis during gluconeogenesis?

Accepted Answer

Fructose-1,6-bisphosphatase

Question 6

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

Accepted Answer

Inability to convert glucose-6-phosphate to glucose, leading to hypoglycemia

Question 7

Which of the following best describes the fate of NADH produced during glycolysis if oxygen is not available?

Accepted Answer

NADH is used to reduce pyruvate to lactate, regenerating NAD$$^+$$

Question 8

Which of the following steps is unique to gluconeogenesis and does not occur in glycolysis?

Accepted Answer

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

Question 9

Why can't even-chain fatty acids contribute to net glucose synthesis in humans?

Accepted Answer

Their breakdown yields only acetyl-CoA, which cannot be converted to pyruvate or oxaloacetate in humans.

Question 10

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

Accepted Answer

To prevent a futile cycle where ATP would be wasted by simultaneous operation of both pathways.

Question 11

Which of the following is a key regulatory step in gluconeogenesis that is inhibited by AMP and stimulated by citrate?

Accepted Answer

Fructose-1,6-bisphosphatase

Question 12

A mutation that increases the activity of phosphofructokinase-1 (PFK-1) would most likely result in which of the following?

Accepted Answer

Increased glycolytic flux and decreased gluconeogenesis

Question 13

Which of the following best describes the role of biotin in gluconeogenesis?

Accepted Answer

It acts as a coenzyme for pyruvate carboxylase, facilitating the carboxylation of pyruvate to oxaloacetate.

Question 14

Which of the following reactions is catalyzed by glucose-6-phosphatase?

Accepted Answer

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

Question 15

Which of the following best explains why the liver is a primary site for gluconeogenesis?

Accepted Answer

The liver contains the necessary enzymes, including glucose-6-phosphatase, to release free glucose into the blood.

Gluconeogenesis and Glycolysis: Pathways and Regulation

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