Exam 4 - Pentose Phosphate Flashcards
What energy molecule does the pentose phosphate pathway produce?
NADPH
The Pentose Phosphate Pathway provides [] requierd as a componenet of nucleotides and coenzymes
Ribose
What is another name for stage 1 of the Pent-Phos pathway?
Oxidative decarboxylation
Stage 1
What enzyme convert glucose 6-phosphate to 6-phosphoglucono-delta-lactone and NADPH
Glucose 6-phosphate dehydrogenase
Stage 1
What does 6-phosphogluconolactonase do?
Converts phosphoglucono-delta-lactone to 6-phosphogluconate
Stage 1
What enzyme converts 6-phosphogluconate to ribulose 5-phosphate, CO2, and NADPH?
6-phosphogluconate dehydrogenase
Stage 1
What does Ribose 5-phosphate isomerase do?
What is the other name for this enzyme?
- converts ribulose 5-phosphate to ribose 5-phosphate
- Pentose phosphate isomerase
What enzymes produce NADPH during the pentose phosphate pathway?
- Glucose 6-phosphate dehydrogenase
- 6-phosphogluconate dehydrogenase
Are the reactions of stage 1 freely reversible?
Negative
What is the summary equation of stage 1?
Glucose 6-P + 2 NADP+ + H2O
——>
Ribulose 5-P + 2 NADPH + CO2
Stage 2 recycles ribulose 5-P to [] intermediates…
glycolytic
Are the reactions of Stage 2 freely reversible?
Yes
What does Phosphopentose Epimerase do?
What is another name for this enzyme….
Interconverts ribulose 5-P and xylulose 5-P
Pentose Phosphate Epimerase
What does the first transketolase do in Stage 2 of the Pentose Phosphate Pathway?
- transfers a two-carbon unit of ketose (xylulose 5-P) to an aldose (ribose 5-P) acceptor
- This creates
- Glyceraldehyde 3-P
- Sedheptulose 7-P
Which enzyme transfers a three carbon unit of sedoheptulose 7-P to glyceraldehyde 3-P to form fructose 6-P and erythrose 4-P??
Transaldolase
What does the 2nd Transketolase do in Stage 2 of the Pentose Phosphate Pathway?
- transfers a two-carbon unit of ketose (xylulose 5-P) to an aldose (erythrose 4-P) acceptor
- This creates
- Glyceraldehyde 3-P
- Fructose 6-P
What is the summar equation for Stage 2 of the Pent-Phos Path?
3 Ribulose 5-P
—>
<—
2 Fructose 6-P + Glyceraldehyde 3-P
Whag is the summary equation for Stages 1 and 2?
Glucose 6-P + 12 NADP+
—>
6 CO2 + 12 NADPH
Why is Erythrose 4-P important and what is the pathway for its “importance”???
- It is used to make tyrosine in humans
- Erythrose 4-P —> Shikimate
- Shikimate acid Pathway
- Shikimate —> Chorismate
- Chorismate Biosyn
- Chorismate —> Phenylalanine
- Phenylalanine —> Tyrosine
