Pentose Phosphate Pathway (PPP)

Question 1

Where does the pentose phosphate pathway (or hexose monophosphate (HMP) shunt occur?

Answer 1

Cytosol

Question 2

What are the two main functions of the pentose phosphate pathway (PPP)?

Answer 2

1. produces ribose-5-phosphate (for nucleotide synthesis)
2. produces NADPH

Question 3

Which enzyme is the rate-limiting enzyme of the pentose phosphate pathway (PPP)?

Answer 3

Glucose-6-phosphate dehydrogenase (G6PD)

Question 4

In the PPP, what happens if ribose-5-p is not needed for nucleotide synthesis?

Answer 4

It is converted into the glycolytic intermediates fructose-6-p and G3P.

Question 5

[Mnemonic]

Pentose** **Phosphate** Pathway = **Ribose** NAD_P_**H Pathway

(how to remember the function of the pentose phosphate pathway)

Answer 5

Pentose** **Phosphate** Pathway = **Ribose** NAD_P_**H Pathway

• A pentose is a 5 carbon sugar (ribose 5-p) and it is produced.
• NADPH has a phosphate and it is also produced.

Question 6

The pentose phosphate pathway (PPP) produces NADPH and ribose-5-p. How does this happen?

Answer 6

Glucose-6-p from glycolysis is shunted to the PPP by G6PD.

Question 7

What are the two main functions of NADPH?

Answer 7

1. synthesis of fatty acids
2. REDUCES glutathione

​​Glutathione is an antioxidant that protects RBCs from oxidative damage caused by free radicals and peroxides.

Question 8

What are the two possible pathways that glucose 6-phosphate can go towards?

Answer 8

1. glycolysis
2. PPP