$$\text{Glucose} \rightarrow \text{CO}_2 + \text{NADPH}$$

Question 1

Which of the following is NOT a primary purpose of the Pentose Phosphate Pathway (PPP)?

Accepted Answer

Direct production of ATP

Question 2

Which enzyme catalyzes the rate-limiting step of the oxidative phase of the PPP?

Accepted Answer

Glucose-6-phosphate dehydrogenase (G6PD)

Question 3

A patient presents with hemolytic anemia after taking an oxidant drug. Which PPP enzyme deficiency is most likely responsible?

Accepted Answer

Glucose-6-phosphate dehydrogenase (G6PD)

Question 4

Which of the following best describes the fate of glucose-6-phosphate (G6P) when a cell requires both NADPH and ribose-5-phosphate (R5P)?

Accepted Answer

The oxidative phase of PPP runs, and products are used directly with minimal carbon recycling

Question 5

Which vitamin deficiency can be clinically assessed by measuring RBC transketolase activity?

Accepted Answer

Vitamin B1 (Thiamine)

Question 6

Which of the following reactions is catalyzed by transketolase in the PPP?

Accepted Answer

Transfer of a 2-carbon unit

Question 7

Which of the following is a direct product of the oxidative phase of the PPP?

Accepted Answer

Ribulose-5-phosphate

Question 8

A high NADPH/NADP$$^+$$ ratio in the cell will have what effect on the PPP?

Accepted Answer

Inhibit G6PD and decrease PPP flux

Question 9

Which of the following is NOT a function of NADPH produced by the PPP?

Accepted Answer

ATP production via oxidative phosphorylation

Question 10

In a rapidly dividing cell, which direction does the PPP primarily run?

Accepted Answer

Oxidative phase runs, products used directly, minimal carbon recycling

Question 11

Which of the following best describes the non-oxidative phase of the PPP?

Accepted Answer

Fully reversible and converts pentoses to glycolytic intermediates

Question 12

Which cofactor is required for transketolase activity in the PPP?

Accepted Answer

Thiamine pyrophosphate (TPP)

Question 13

A cell in a nucleotide-demand state will direct glycolytic intermediates into the PPP to produce which molecule, and which phase is bypassed?

Accepted Answer

Ribose-5-phosphate; oxidative phase

Question 14

Which of the following best explains why red blood cells are highly dependent on the PPP?

Accepted Answer

They require NADPH to maintain reduced glutathione and protect against oxidative damage

Question 15

Which hormonal state in the liver increases G6PD expression and PPP activity?

Accepted Answer

High insulin/glucagon ratio

Question 16

Which of the following is a net reaction for maximizing NADPH output in the PPP?

Accepted Answer

$$	ext{Glucose} ightarrow 	ext{CO}_2 + 	ext{NADPH}$$

Question 17

Which enzyme catalyzes the conversion of ribulose-5-phosphate to xylulose-5-phosphate?

Accepted Answer

Epimerase

Question 18

Which of the following is a clinical use of measuring RBC transketolase activity?

Accepted Answer

Assessing functional vitamin B1 (thiamine) status

Question 19

Which of the following best describes the role of the PPP in detoxification reactions?

Accepted Answer

Provides NADPH for cytochrome P450 enzymes

Question 20

Which of the following statements about the non-oxidative phase of the PPP is correct?

Accepted Answer

It allows for the synthesis of ribose-5-phosphate without NADPH production

Pentose Phosphate Pathway (PPP): Structure, Function, and Regulation

Study Guide - Practice Questions