lecture 20 pentose phosphate pathway Flashcards
what is the point of the pentose phosphate pathway?
gives our cells a way to produce NADPH, which is an important reducing agent and is used in biosynthesis, dna synthesis, etc
PPP allows for which kind of sugars?
3-7 carbons
what’s phase I of PPP?
oxidative stage. turns 2 NADP+ + glucose-6-phosphate + H2O –> ribose-5-phosphate + 2 NADPH + 2 H+ + CO2
glucose is broken into __ generating ___
ribose-5-phosphate, NADPH
what transformation happens from glucose to ribose?
decarboxylated to ribulose
what’s the delta G situation of phase I?
irreversible, large negative delta G
oxidative phase is controlled by what?
availability of NADP+. G6P is competitively inhibited by NADPH
whats phase II of PPP?
nonoxidative phase. 3 ribose 5 phosphate –> 2 f-6P + 1 GAP.
phase 2 consists of __ reactions that interconvert 5 carbon sugars into new forms
3
how are the PPP and glycolysis linked?
transketolase and transaldolase
is phase 2 reversible?
yes
what would you do if the cell needs more ribose than NADPH?
run phase 2 backwards
what would you do if cell needs both ribose and NADPH?
run phase 1 forwards
what do you do if cell needs more NADPH than ribose?
run phase 1, and then use the ribose-5-phosphate for gluconeogensis: Ribose -> GAP -> fructose 6 phosphate -> glucose 6 phosphate
what do you do if cell needs ATP and NADPH?
run phase 1 and then use your Ribose to run glycolysis- produce pyruvate and ATP
how is PPP regulated
competitively and through feedback inhibition; inhibited by its own product, NADP+. competitively inhibited by NADPH
tissues with active pentose phosphate pathways
fat and steroid synthesis, adrenal glands, liver, tests, mammary
how are red blood cells using the PPP?
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
