Pentose Phosphate Pathway Flashcards
What are the two phases of PPP
- Oxidative; redox reactions catalized by enzymes called dehydrogenases to produce NADPH
- Non -oxidative; recycling pathway
What are the major products form oxidative phase
- Ribose 5-phosphate; for nucleotide synthesis
2. 2 NADPH; for biosynthetic reactions and antioxidant reducing power
what are the glycolytic intermediates from non oxidative pathway
- glyceraldehyde 3-phosphate
2. fructose -6-phosphate
PPP has no ____production
energy; no ATP
PPP is a ____pathway
fermentative; no oxygen
The non oxidative pathway takes 1-ribose -5-phosphate and _____phosphate and rearranges back to _____to allow continuation of oxidative phase
1 xylulose 5-phosphate; glucose 6-phosphate
NOn oxidative phase is active only in tissues in which ____is needed in high amounts
NADPH
Where does PPP occur
All tissues; anywhere that requires a lot of ribose 5-phosphate for new DNA synthesis:-bone marrow, skin, oral and intestinal mucosa, tumors
Where is another place that PPP can occur
Anywhere that needs a lot of NADPH:
- Tissues that are synthesizing fatty acids, cholesterol or steroid hormones - liver, adipose, adrnal cortex
- Tissues that exposed to high levels of oxygen- erythrocytes, cornea and lens
1st step of PPP is rate limiting step where you convert glucose 6 phosphate to ____. NADP+ gets reduced to _____ and 6-phosphogluconate gets converted to _____
6-phosphogluconate (ends in -ate means you have acid; oxidizing glucose to an acid sugar);
NADH; ribulose 5-phosphate.
We need NADPH as a reducing agent for oxidative stress because
a lot of it comes from electron transport
What is glutathione (GSH)
3 aa compound that has sulfur group (cysteine) and forms disulfide bonds and donates H and reduce oxidized compounds. We have to regenerate the reduced form of glutathione in order to keep repairing oxidized tissues and to do this we need NADPH. It maintains the reduced form of glutathione that helps repair oxidized molecules.
What are the three aa that make up glutathione
glutamate, cysteine, glycine
The oxidative phase of PPP has ____steps. 2 involve _____reactions that produce _____
4; dehydrogenase; NADPH
The first step is the ____limiting step that forms the first ____.
rate; NADPH
The second step is an intermediate step that forms a _____. 6 phosphoglucanate is acted on by 6 phosphoglucanate dehydrogenase and form another ____ which becomes decarboxlyated. Then phosphopentose isomerase converts ketose to ____ and lose CO2 to form ribulose 5 phosphate
lactone; NADPH; aldehyde
What are the starting points of non oxidative phase
Ribose 5 phosphate and xylulose 5 phosphate
What is the intermediate step of non oxidative phase
Rearranging carbons to get intermediates that we can use
Xylulose 5-phosphate activates ____which activates PK2 to stimulate glycolysis
protein phosphatase 2A;
Which 2 enzymes transfer 2C or 3C ketose units to aldose acceptors
transketolase and transaldolase
transketolase requires ____ to transfer 2 C
thiamine
Which 2 enzymes are good intermediates to start the PPP pathway for the oxidative phase
- Fructose 6-phosphate
2. Glyceraldehy 3-phosphate
What is Wernicke Korsakoff syndrome
Caused by a mutation in transketolase and severe deficiency in thiamine. It is common in alcoholics due to poor intestinal absorption of the vitamin.
High NADPH levels inhibit ____. This serves to make glucose 6-phosphate available for glycolysis.
glucose 6 phosphate dehydrogenase
What is the role of NADPH in the RBC
For repair of oxidative damage
When free radicals are produced it causes the production of ____ that can damage cell membranes and cause ___
peroxide; hemolysis (lyse) or hemolytic anemia
What does glucose 6 phosphate dehydrogenase deficiency cause
decreases intracellular NADPH and GSH
G6PDH deficiency protects against
malaria
