Pentose Phosphate Pathway

Question 1

glucose 6-phosphate –> 6-phosphogluconolactone

Answer 1

glucose 6-phosphate dehydrogenase, produce 1 NADPH

Question 2

6-phosphogluconolactone –> 6-phosphogluconate

Answer 2

lactonase

Question 3

6-phosphogluconate -> ribulose 5-phosphate

Answer 3

6-phosphogluconate dehydrogenase, produce 1 NADPH, produce 1 CO2

Question 4

ribulose 5-phosphate products

Answer 4

ribose 5-phosphate, xylose 5-phosphate

Question 5

products of non-oxidative phase

Answer 5

fructose 6-phosphate, GAP (C3)

Question 6

Oxidative Phase Reaction

Answer 6

glucose 6-phosphate + 2 NADP + H2O –> ribose 5-phosphate + 2 NADPH + CO2

Question 7

Non-oxidative Phase Reaction

Answer 7

3 pentoses (2 xylulose 5-P, 1 ribose 5-P) 2 hexoses (fructose 6-P) + 1 triose (glyceraldehyde 3-P)

Question 8

Cell needs ribose phosphates and NADPH

Answer 8

low levels NADPH stimulate glucose degradation, oxidative phase produces NADPH and ribose phosphates

Question 9

Cell needs more ribose phosphates than NADPH

Answer 9

rapidly dividing cells need ribose but have enough NADPH, high NADPH inhibits oxidative phase, glucose processed via glycolysis, ribose phosphates synthesize via non-oxidative phase, glycolytic intermediates fructose phosphate and GAP converted to xylulose and ribose 5-phsophates

Question 10

Cell needs more NADPH than ribose phosphates

Answer 10

adipose tissue, need large amounts NADPH for fatty acid synthesis, NADPH generated through PPP but don’t use all pentose phosphates, non-oxidative phase converts surplus phosphates to fructose 6-phosphate and glyceraldehyde 3-phosphate for gluconeogenesis, produce glucose to be oxidized by PPP

Question 11

Cell needs NADPH and ATP

Answer 11

low NADPH levels stimulate oxidative phase to form NADPH, non-oxidative phase generates glycolytic intermediates fructose 6-phosphate and glyceraldehyde 3-phosphate to be processed by glycolysis for NADH and ATP