lecture 20 pentose phosphate pathway

Question 1

what is the point of the pentose phosphate pathway?

Answer 1

gives our cells a way to produce NADPH, which is an important reducing agent and is used in biosynthesis, dna synthesis, etc

Question 2

PPP allows for which kind of sugars?

Answer 2

3-7 carbons

Question 3

what’s phase I of PPP?

Answer 3

oxidative stage. turns 2 NADP+ + glucose-6-phosphate + H2O –> ribose-5-phosphate + 2 NADPH + 2 H+ + CO2

Question 4

glucose is broken into __ generating ___

Answer 4

ribose-5-phosphate, NADPH

Question 5

what transformation happens from glucose to ribose?

Answer 5

decarboxylated to ribulose

Question 6

what’s the delta G situation of phase I?

Answer 6

irreversible, large negative delta G

Question 7

oxidative phase is controlled by what?

Answer 7

availability of NADP+. G6P is competitively inhibited by NADPH

Question 8

whats phase II of PPP?

Answer 8

nonoxidative phase. 3 ribose 5 phosphate –> 2 f-6P + 1 GAP.

Question 9

phase 2 consists of __ reactions that interconvert 5 carbon sugars into new forms

Answer 9

3

Question 10

how are the PPP and glycolysis linked?

Answer 10

transketolase and transaldolase

Question 11

is phase 2 reversible?

Answer 11

yes

Question 12

what would you do if the cell needs more ribose than NADPH?

Answer 12

run phase 2 backwards

Question 13

what would you do if cell needs both ribose and NADPH?

Answer 13

run phase 1 forwards

Question 14

what do you do if cell needs more NADPH than ribose?

Answer 14

run phase 1, and then use the ribose-5-phosphate for gluconeogensis: Ribose -> GAP -> fructose 6 phosphate -> glucose 6 phosphate

Question 15

what do you do if cell needs ATP and NADPH?

Answer 15

run phase 1 and then use your Ribose to run glycolysis- produce pyruvate and ATP

Question 16

how is PPP regulated

Answer 16

competitively and through feedback inhibition; inhibited by its own product, NADP+. competitively inhibited by NADPH

Question 17

tissues with active pentose phosphate pathways

Answer 17

fat and steroid synthesis, adrenal glands, liver, tests, mammary

Question 18

how are red blood cells using the PPP?

Answer 18

red blood cells have glucose-6-dehydrogenase because they are very sensitive to reactive oxygen species that can cause oxidation. so their glutathione sacrifices itself to get oxidized instead of cell proteins. NADPH reduces glutathione, making NADPH necessary for detoxifying blood