Pentose Phosphate Pathway & NADPH

Question 0

What are the important features of the pentose phosphate pathway?

Answer 0

• no ATP produced
• loss of CO2, therefore irreversible
• controlled by NADP+/NADPH balance
• utilised when [ATP] is high

Question 1

What are the important products of the pentose phosphate pathway?

Answer 1

• Ribose for nucleic acid synthesis (note: can re-enter glycolysis)
• NADPH production

Question 2

Name the enzyme catalysing the pentose phosphate pathway?

Answer 2

Glucose-6-P dehydrogenase

Question 3

Which organs have a high amount of pentose phosphate activity?

Answer 3

Liver

RBCs

Adipose

Question 4

What are the consequences of glucose-6-phosphate dehydrogenase deficiency?

Answer 4

Low NADPH

Therefore vulnerable to oxidant stresses

e.g. RBCs = disulfide bonds formed —-> proteins aggregate and form Heinz bodies ——–> haemolysis

Question 5

What is NADPH used for?

Answer 5

Anti-oxidant, resists oxidant stresses

e.g. keeps -SH reduced (prevents disulfide bond formation)

prevents cataract formation, Heinz bodies formation

Question 6

How can pyruvate be converted to acetyl-CoA for entry into the TCA cycle? Which enzyme catalyses the reaction? Where does this occur?

Answer 6

(pyruvate dehydrogenase)
Pyruvate + CoA ———————–> Acetyl CoA + CO2
NAD+ ——-> NADH

Pyruvate transported into mitochondrial matrix
Cofactors from Vitamin B
Activated by low energy signals
Irreversible reaction