Chapter 12 The Pentose Phosphate Pathway Flashcards
What are the products of the oxidative phase of the pentose phosphate pathway?
5 carbon sugar ribose 5- phosphate and 2 molecules of NADPH.
What are the products of the non-oxidative phases of the pentose phosphate pathway?
glucose-6-phosphate which allows the continued production of NADPH.
In what cells is the PPP active?
active in rapidly dividing cells and cells experiencing oxidative stress.
What enzymes are involved in the oxidative phases of the pentose phosphate pathway?
dehydrogenase, lactonase, isomerase, epimerase.
What enzymes are involved in the non-oxidative phases of the pentose phosphate pathway?
transaldolase, transketolase
How many carbon fragments are transferred in transketolation?
2 carbon fragments from the ketose donor.
How many fragments are transferred in transaldolation?
3 carbon fragments.
Which reaction is catalyzed by the dehydrogenase enzyme?
Glucose 6-phosphate to 6-phosphogluconolactone.
How is the first step of the PPP regulated?
NADP+ levels are high dehydrogenase is activated.
What reaction is catalyzed by lactonase?
6-phosphogluconolactone to 6-phosphogluconate
How is 6-phosphogluconate converted to ribulose 5-phosphate
decarboxylation, loss of CO2.
In which steps is NADPH generated?
Glucose 6-phosphate to 6-phosphogluconolactone.
6-phosphogluconate to ribulose 5-phosphate.
What reaction is catalyzed by isomerase?
D-ribulose 5-phosphate to D- ribose 5-phosphate
What reaction is catalyzed by epimerase?
D-ribulose 5-phosphate to Xylulose 5-phosphate.
What are the transketolation reactions that take place?
- Xylulose 5-phosphate and D-ribose phosphate giving sedoheptulose 7-phosphate and glyceraldehyde 3-phosphate.
- Xylulose 5-phosphate and Erythrose 4-phosphate giving glyceraldehyde 3-phosphate and fructose 6-phosphate.
Which reaction uses a TPP cofactor?
Transketolation, because we are not breaking a favorable C-C bond, we need to use the pretend carbonyl.
What is the transadolation reaction that takes place?
glyceraldehyde 3-phosphate and sedoheptulose-7-phosphate forming erythrose 4-phosphate and fructose-6-phosphate.
What is the relationship between Glucose 6-phosphate and NADP+
Concentration of NADP+ high, glucose 6-phosphate is stimulated to move through the PPP.
When NADP+ is converted to NADPH the concentration is much lower and glucose is shuttled into glycolysis.
How is Xylulose 5-phosphate the master regulator?
Xylulose 5-phosphate activates phosphatases resulting in the dephosphorylation of the dual PFK-2/FBPase protein
This results in phosphorylation of F-6-P to F-2,6-P enhancing glycolysis.
What is the Wernicke’s Korsakoff syndrome?
deficiency in thiamine Vitamin B1, failure of the pentose phosphate pathway.
Glutathione
acts a reducing agent and is important in maintaining the redox balance of the cell.
How is glutathione generated?
NADPH generates glutathione.
How is the NADPH pool regenerated?
Through the pentose phosphate pathway.
What is function of reduced glutathione?
protects the cell by destroying hydrogen peroxide and hydroxyl free radicals.
