Pentose Phosphate Pathway

Question 1

Function

Answer 1

produce NADPH and Ribulose-5P

Question 2

2 phases

Answer 2

1. Oxidative phase

2. Nonoxidative phase

Question 3

Glucose 6P -> 6-Phosphogluconolacetone

Answer 3

• oxidative phase
• reducing NADP+ to NADPH
• enzyme: GLUCOSE 6 PHOSPHATE DEHYDROGENASE

Question 4

6-Phosphogluconolacetone -> 6Phosphogluconate

Answer 4

• hydration
• oxidative phase
• enzyme: GLUCONOLACTONASE

Question 5

6-Phosphogluconate -> Ribulose 5P

Answer 5

• oxidative phase
• oxidative carboxylation
• NADP+ reduced to NADPH
• enzyme: 6-PHOSPHOGLUCONATE DEHYDROGENASE

Question 6

Ribulose 5P -> Ribose 5P

Answer 6

• nonoxidative phase
• used for nucleotide biosynthesis or production of F6P
• enzyme: PHOSPHOPENTOSE ISOMERASE

Question 7

Ribulose 5P -> Xylulose 5P

Answer 7

• nonoxidative phase

- enzyme: PHOSPHOPENTOSE EPIMERASE

Question 8

Ribose 5P + Xylulose 5P-> Fructose 6P + Glyceraldehyde 3P

Answer 8

-enzymes: TRANSKETOLASE / TRANSALDOLASE

Question 9

Control

Answer 9

uses G6P
if ATP low-> glycolysis
if NADPH low -> PPP

Question 10

Regulation: rate of PPP

Answer 10

nonoxidative:
depends on availability of enzyme substrates

oxidative:
allosteric regulation of glucose6P DH
activated by: high NADP+
inhibited by: low NADP+