Pentose-Phosphate Shunt Flashcards
1
Q
Pentose phosphate shunt
A
- diversion of glucose molecules from glycolysis
- involves: G-6-P, F-6-P, glyceraldehyde-3-P
- makes 5 carbon sugars (ribose and deoxyribose)
- makes NADPH for protection from oxidative stress and for reducing equivalents in biosynthetic pathways
2
Q
Oxidative branch
A
- irreversible
- controlled by NADP availability
- produces NADPH
- releases electrons
- oxidative decarboxylation drives the branch: ie, the oxidation is converting the sugar to a beta-keto acid which allows the decarboxylation
3
Q
Non-oxidative branch
A
- every step is a: inter-conversion of aldo and keto sugar
- keto sugar is longer
- original keto sugar becomes an aldo sugar and vice versa
- enzymes = transketolase and transaldolase
- start with three 5C sugars and end with two 6C sugars and a 3C sugar
4
Q
transketolase
A
in the nonoxidative branch
- transfers 2 carbons
5
Q
transaldelase
A
in the nonoxidative branch
- transfers 3 carbons
6
Q
glutathione (GSH)
A
- major reducing agent in the cell
- oxidized form = G-S-S-G (which must be reduced back)
- G-S-S-G is reduced by NADPH
7
Q
Mn-superoxide dismutase
A
- In mitochondria
- converts superoxide into peroxide and oxygen
8
Q
Cu,Zn- superoxide dismutase
A
- in cytosol
- converts superoxide into peroxide and oxygen
9
Q
Glucose-6-Phosphate Dehydrogenase deficiency
A
- can’t reduce NADP
- no NADPH meanse you can’t reduce G-S-S-G
- means limited glutathione reductase activity
- results in RBCs whose membranes are always oxidatively stressed (glutathione reduces hydrogen peroxide)
- results in hemolytic anemia
10
Q
Wernicke-Korsakoff Syndrome
A
- neuropsychiatric problem due to reduced thiamine levels
- thiamine deficiency causes decreased transketolase activity, tissue has an oxidative branch which results in C5 sugar build up causing metabolic derangement
- could be due to alcohol related malnourishment
