Q: What is the overall reaction for the oxidative phase of the pentose phosphate pathway?

$$\mathrm{Glucose\text{-}6\text{-}phosphate + 2 NADP^+ + H_2O \rightarrow Ribulose\text{-}5\text{-}phosphate + 2 NADPH + 2 H^+ + CO_2$}$$

Q: Which of the following reactions is catalyzed by transketolase in the non-oxidative phase of the pentose phosphate pathway?

$$\mathrm{Xylulose\text{-}5\text{-}phosphate + Ribose\text{-}5\text{-}phosphate \rightarrow Glyceraldehyde\text{-}3\text{-}phosphate + Sedoheptulose\text{-}7\text{-}phosphate}$$

Question 1

Which of the following is a primary function of the pentose phosphate pathway in cells?

Accepted Answer

To produce NADPH for reductive biosynthesis and ribose-5-phosphate for nucleotide synthesis

Question 2

Which enzyme catalyzes the first committed step of the oxidative phase of the pentose phosphate pathway?

Accepted Answer

Glucose-6-phosphate dehydrogenase

Question 3

What is the overall reaction for the oxidative phase of the pentose phosphate pathway?

Accepted Answer

$$\mathrm{Glucose	ext{-}6	ext{-}phosphate + 2 NADP^+ + H_2O ightarrow Ribulose	ext{-}5	ext{-}phosphate + 2 NADPH + 2 H^+ + CO_2$}$$

Question 4

Which of the following best describes the role of NADPH produced in the pentose phosphate pathway?

Accepted Answer

It acts as a reducing agent in biosynthetic reactions and in the regeneration of reduced glutathione

Question 5

A deficiency in glucose-6-phosphate dehydrogenase (G6PD) would most likely result in which clinical consequence?

Accepted Answer

Increased risk of hemolytic anemia due to inability to detoxify reactive oxygen species

Question 6

Which of the following reactions is catalyzed by transketolase in the non-oxidative phase of the pentose phosphate pathway?

Accepted Answer

$$\mathrm{Xylulose	ext{-}5	ext{-}phosphate + Ribose	ext{-}5	ext{-}phosphate ightarrow Glyceraldehyde	ext{-}3	ext{-}phosphate + Sedoheptulose	ext{-}7	ext{-}phosphate}$$

Question 7

Which of the following best explains why the pentose phosphate pathway is especially active in rapidly dividing cells?

Accepted Answer

These cells need ribose-5-phosphate for nucleotide and nucleic acid synthesis

Question 8

Which of the following is a product of the non-oxidative phase of the pentose phosphate pathway that can re-enter glycolysis?

Accepted Answer

Glyceraldehyde-3-phosphate

Question 9

Which of the following statements about the regulation of the pentose phosphate pathway is correct?

Accepted Answer

It is primarily regulated by the availability of NADP$$^+$$

Question 10

A patient with a mutation in transaldolase would have difficulty converting which of the following?

Accepted Answer

Sedoheptulose-7-phosphate and glyceraldehyde-3-phosphate to erythrose-4-phosphate and fructose-6-phosphate

Question 11

Which of the following best describes the fate of ribose-5-phosphate when the cell does NOT require nucleotides but needs NADPH?

Accepted Answer

It is converted to glucose-6-phosphate via the non-oxidative phase

Question 12

Which of the following reactions in the pentose phosphate pathway directly produces CO$$_2$$?

Accepted Answer

$$\mathrm{6	ext{-}phosphogluconate ightarrow Ribulose	ext{-}5	ext{-}phosphate}$$

Question 13

Which of the following best explains why red blood cells are highly dependent on the pentose phosphate pathway?

Accepted Answer

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

Question 14

Which of the following is NOT a direct product of the pentose phosphate pathway?

Accepted Answer

Fructose-1,6-bisphosphate

Question 15

Which of the following best describes the role of glutathione in cells, as related to the pentose phosphate pathway?

Accepted Answer

It detoxifies reactive oxygen species using NADPH generated by the pentose phosphate pathway

Question 16

Which of the following best explains the importance of the reversible reactions in the non-oxidative phase of the pentose phosphate pathway?

Accepted Answer

They allow the cell to balance the need for NADPH and ribose-5-phosphate independently

Pentose Phosphate Pathway: Structure, Function, and Regulation

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