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24 Cards in this Set
- Front
- Back
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What is the Pentose Phosphate Path?
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It branches off of glycolytic path and then goes back in
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What is the point of the PP-Path?
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Used as extra control of glycolysis
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What are the metabolic uses of the pp-path?
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1) Produce NADPH
2) Produce Pentose sugars 3) Utilize pentose sugars |
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How can this path be split?
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Oxidative and non-oxidative steps
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Why do cells have NAD+ and NADP?
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They're both dif cofactors
NADH: Used to make ATP NADPH: used for synthesis of FA and Cholesterol |
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Which has a higher concentration in the cytosol?
a) NAD+ or NADH b)NADP+ or NADPH |
a) NAD+ (glycolysis is in th cystosol)
b) NADPH (FA syn is in the cytosol) |
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Where does the PP-path branch off of glycolysis? Where does it reenter?
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-Leaves at G6P
-Returns at F6P and GAP |
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Which cells do the PP-path?
Which cells don't and why? |
-Adipose, liver and blood cells
-Muscle cells don't cuz you want G6P to make ATP |
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What are the 3 staes of the PP-path?
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1) Oxidative rxns (IRREV)
2)Isomerization and Epimerization (REV) 3) C-C bond cleavage and formation rxns (REV) |
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What are the 3 oxidative steps?
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1)G6P-->6-Phosphoglu-delta-lactone
use 3NADP+ -->3NADPH+3H+ enz: G6P DH 2) 6-Phosphoglucono-d-lactone --> 6-Phosphogluconate use 3H2O --> 3 H=+ enz: 6-phosphoglucono-lactamase 3)6-Phosphogluconate ---> Ribulose-5-P use: 3NADP+-->3NADPH + 3CO2 Enz: 6-phosphogluconate dehydrogenase |
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What is the poitn of the 5oxidative reactions?
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Produce NADPH and Ru5P
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What is the regulatory step of the oxidative reactions?
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-The 1st step
G6P-->6-phosphoglucono-d-lactone |
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What is isomerization?
What is epimerization? |
Isomerization: interchange of groups between C
Epimerization: interchange of groups on 1 C |
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What are rxns 4 and 5 of the PP-path?
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Rxn 4: Isomerization
Ru5P --> Ribulose-5-P Rxn 5: Epimerization: Ru5P --> Xylulose-5-P Overall Rxn: 3Ru5P--> R5P + 2Xu5P |
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What is R5P involved in?
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Nucleotide synthesis.
If too much R5P, convert it nto F6P and GAP |
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What are the C-C bond cleavage and formation reactions?
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6) R5P + Xu5P --> Sedoheptulose-7-phosphate (S7P) + GAP
Enz: Transketolase 7) GAP + S7P --> F6P + Erythrose-4-P (E4P) Enz: Transaldolase 8) E4P + Xu5P --> F6P + GAP Enz: Transketolase **The 2 trnsketolases used are different** Overall, get 1 GAP and 2 F6P |
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What is the overall reaction for the pp-path?
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3G6P + 6NADP+ + 3H2O <--> 6NADPH + 3H+ + 3CO2 + 2 F6P + GAP
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How is the PP-path regulated?
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-By the amount of G6P
-G6P depends on the actions of PFK and G6P-DH -Amt of R5P |
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What inhibits PFK?
What inhibits G6P-DH? |
PFK: inhibited by ATP
G6PDH: inhibited by NADPH |
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If you need more.....
a) Pentose-P and NADPH b)NADPH than pentose c) Pentose than NADPH How is the PP-Path reguated? |
a)Oxidative part of the path dominates
b) Transaldolase/ketolases convert excess pentose sugars to F6P and GAP, which can be used through glycolysis or recycled by gluconeogenesis c) F6P and GAP can be converted into 5-C sugars by reversing transaldolase/ketolases rxns |
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What role does NADPH play in RBC?
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Need glutathione in cell mb, but use it to reduce H2O2 to GSSG, through the glatathione peroxidase
-NADPH is then used to reduce GSSG to GSG, through glutathione reductase 2GSH + H2O2 --> GSSG + ROH + H2O GSSG + NADPH--> GSH + NADP+ |
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What is G6PDH deficincy? What happens?
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Mutation in G6PDH. X-linked trait. Mutant G6PDH breaks down quickly .: problem harder to kep high levl of GSH
-Self-limiting cuz mature RBC don't have a nucleus so they can't replace the degrade enz, so they lyse and new RBC are developed which have more enz and can deal with the oxidative stress |
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What role does NADPH play in RBC?
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Need glutathione in cell mb, but use it to reduce H2O2 to GSSG, through the glatathione peroxidase
-NADPH is then used to reduce GSSG to GSG, through glutathione reductase 2GSH + H2O2 --> GSSG + ROH + H2O GSSG + NADPH--> GSH + NADP+ |
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What is G6PDH deficincy? What happens?
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Mutation in G6PDH. X-linked trait. Mutant G6PDH breaks down quickly .: problem harder to kep high levl of GSH
-Self-limiting cuz mature RBC don't have a nucleus so they can't replace the degrade enz, so they lyse and new RBC are developed which have more enz and can deal with the oxidative stress |
