Pentose Phosphate Pathway

Question 1

What is PPP also known as?

Answer 1

• hexose monophosphate shunt

- phosphogluconate pathway

Question 2

What is NADPH used in?

Answer 2

anabolism (building of things)

Question 3

What is NADH used in?

Answer 3

catabolism (breaking down things)

Question 4

This pathway has two phases: what are they?

Answer 4

oxidative phase - production of energy and pentoses

non-oxidative phase - rearrangement of pentoses (C5) back to hexoses (C6)

Question 5

Provide a summary of the oxidative phase.

Answer 5

C6 –> C5 + CO2 + 2NADPH + 2H+

Question 6

Provide a summary of the non-oxidative phase.

Answer 6

C5 –> C6

Question 7

From 6C6 –> 6C5, how many NADPH are released?

Answer 7

12

Question 8

How many ATP can be produced from NADPH ?

Answer 8

30 ATP

2.5ATP/NADPH

Question 9

What are the 2 major reasons for having this pathway?

Answer 9

1. produce NADPH - reducing power: needed for reductive biosynthesis or counter damaging effects of oxygen radicals (fat cells or erythrocytes/lenses)
2. make pentoses: in bone marrow/skin and intestinal mucosa used for RNA/DNA and coenzymes (ATP, NADH, FADH2, and CoA)

Question 10

Name the enzyme for:

Glc 6 P –> Gluconolacctone 6-P

Answer 10

Glc 6 P dehydrogenase

Question 11

Name the enzyme for:

Gluconolactone 6-P –> gluconate 6P

Answer 11

lactonase

Question 12

Name the enzyme for:

gluconate 6P –> ribulose 5P

Answer 12

gluconate 6P dehydrogenase

Question 13

Name the enzyme for:

ribulose 5P –> ribose 5P

Answer 13

ribose P isomerase

Question 14

Name the cofactors for:

Glc 6 P –> Gluconolacctone 6-P

Answer 14

NADP+ –> NADPH + H+

Question 15

Name the cofactors for:

Gluconolactone 6-P –> gluconate 6P

Answer 15

H2O consumed

Question 16

Name the cofactors for:

gluconate 6P –> ribulose 5P

Answer 16

NADP+ is converted to NADPH + H+

CO2 released

Question 17

Name the cofactors for:

ribulose 5P –> ribose 5P

Answer 17

no cofactors

Question 18

Describe step 1 in the non-oxidative phase of PPP

Answer 18

Ribulose 5P is either converted into:
-xylulose 5P by ribose 5P epimerase
OR
-ribose 5P by ribose P isomerase

Question 19

Describe step 2 in the non-oxidative phase of PPP

Answer 19

C5 + C5 –> C7 + C3

xylulose 5P + ribose 5P –> glyceraldehyde 3P + sedoheptulose 7P

(uses a transketolase which uses TPP)

Question 20

Describe step 3 in the non-oxidative phase of PPP

Answer 20

C7 + C3 –> C6 + C4

Ga3P + sedoheptulose 7P –> fructose 6P and erythrose 4P

(uses a transaldolase which uses Schiff-Base linkage)

Question 21

Describe step 4 in the non-oxidative phase of PPP

Answer 21

C4 + C5 –> C6 + C3

erythrose 4P + xylulose 5P –> fructose 6P + Ga3P

(uses a transketolase TPP)

Question 22

Describe step 5 in the non-oxidative phase of PPP

Answer 22

C3 + C3 –> C6

Ga3P –> DHAP + Ga3P –> fructose 1,6, bisP —>fructose 6P

Question 23

Name the enzyme:

Ga3P –> DHAP + Ga3P

Answer 23

triose P isomerase

Question 24

Name the enzyme:

Ga3P –> fructose 1,6, bisP

Answer 24

aldolase

Question 25

Name the enzyme:

Fructose 1,6, bisP –> fructose 6 P

Answer 25

Frc 1,6, bisP