Pentose Phosphate Pathway

Question 1

What are oxygen radicals?

Answer 1

• Oxygen can form reactive oxygen species (ROS)
• Oxidative stress occurs when ROA are produced faster than they can be removed
• these defense mechanisms include a number of enzymes and Vitamin C and E
• Cells have endogenous defenses to convert free radicals to non-toxic species

Question 2

What is gluathionine?

Answer 2

• Reduced glutathione can detoxify hydrogen peroxide (glutathione peroxidase)
• Oxidized form of glutathione doesn’t have protective properties so with the help of NADPH, glutathione reductase reduces glutathione so that it can reduce hydrogen peroxide again

Question 3

Why are RBC’s reliant on PPP?

Answer 3

RBC are completely reliant on the Pentose Phosphate Pathway because they don’t have glutathione peroxidase.

Question 4

Provide a brief overview of PPP.

Answer 4

Overview: it oxidizes G6P to intermediates of the glycolytic pathway, generating NADPH and ribose 5-phoshpate for nucleotide synthesis. The NADPH is utilized for reductive pathways (FA and Cholesterol Biosynthesis, detoxification of drugs, steroid synthesis and glutathione defense system, ) SYNTHESIS PATHWAYS

Question 5

Describe the irreversible oxidative rxns in PPP.

Answer 5

-NADPH is generated from the irreversible oxidation of G6P to a pentose (Ribulose 5-phosphate) by Glucose 6-phosphate Dehydrogenase

Question 6

Describe the reversible nonoxidative rxns in PPP.

Answer 6

• Ribulose 5-phoshpate is converted to ribose 5-phosphate and to intermediates of the glycolytic pathway
• ribose 5-phosphate provides the sugar for nucleotide synthesis
• Fructose-6-phosphate and glyceraldehyde-3-phosphate used as substrates for glycolysis (fed state) or gluconeogenesis (fasting state)
• enzymes are transketolase (TPP dependent)

Question 7

What happens when there is a deficiency in glucose 6 phosphate dehydrogenase?

Answer 7

• hemolytic anemia when RBC are exposed to oxidative stress because of inadequate NADPH production (less antioxidant activity of glutathione)
• Oxidative stress: infections, fava beans and certain drugs
• X-linked recessive fashion (disease protects against malaria)

Question 8

What are heinz bodies?

Answer 8

• (oxidative hemoglobin precipitates within RBCs)
• occus when there is glucose 6 phosphate dehydrogenase

Question 9

Where does the PPP occur?

Answer 9

-occurs in the cytosol

Question 10

What types of reactions are invovled in PPP?

Answer 10

-two irreversible, oxidative rxns and a series of reversible sugar-phosphate interconversions

Question 11

What essential molecule does PPP provide for the body?

Answer 11

-provides a major portion of the body’s NADPH (biochemical reductant)

Question 12

What does type of molecule does PPP allow the body to use?

Answer 12

-provides a mechanism for the metabolic use of 5 carbon sugars obtained from the diet

Question 13

Does PPP use ATP?

Answer 13

-NO ATP IS USED/PRODUCED IN THE PATHWAY