Lecture 6: Pentose Phosphate Pathway

Question 1

Name the phases of PPP and the products of each:

Answer 1

1. Oxidative phase products:
   
   • makes both NADPH and Ru5P
2. Non-Oxidative products:
   
   • makes both F6P and GAP

Question 2

Regulation characteristics of PPP:

Answer 2

• high [NADP+] favors PPP
• low [NADP+] favors glycolysis

1. Need R5P > NADPH
   
   • run non-Oxidative in reverse.
2. Need R5P = NADPH
   
   • run oxidative only.
3. Need R5P < NADPH
   
   • run oxidative to get NADPH
   • then carbon shuffle to get R5P —> F6P + GAP
4. Need both NADPH and ATP:
   
   • run oxidative to get NADPH
   • then carbon shuffle to get R5P —> F6P and GAP
   • glycolysis for ATP.

Question 3

Describe the effects of G6P dehydrogenase deficiency, positive and negative:

Answer 3

• Leads to low NADPH production, which cannot detoxify reactive oxygen species
• G6P + oxidative stress —> hemolytic anemia

-Resistance to malaria:
~plasmodium falciparum is very sensitive to oxidative stress, which lives in RBCs and requires NADPH.

Question 4

Explain the purpose of Glutathione:

Answer 4

-helps prevent damage by reactive oxygen species.
-NADPH keeps GSH in reduced form.
~GSSG is oxidized form
-GSH donates e- to relieve oxidative stress.
-NADPH donates e to GSSG to restore its reduced form.