CPR 03 - Pentose Phosphate Pathway

Question 1

What are some other names for the pentose phosphate pathway?

Answer 1

Hexose monophosphate shunt

6-phosphogluconate pathway

Question 2

Where does the PPP take place in the cell and what is its purpose?

Answer 2

Question 3

In which cells is the PPP active and what is it specifically used for?

Answer 3

Question 4

Answer 4

Question 5

Answer 5

Question 6

When/Why is the nonoxidative phase of the PPP performed?

Answer 6

Question 7

Answer 7

Question 8

What enzymes and coenzyme convert ribose5P and xylulose5P into the glycolytic intermediates? What are those glycolytic intermediates?

Answer 8

Enzyme - Transketolase and transaldolase

Coenzyme - TPP (thiamine pyrophosphate)(only used by transketolase)

Glycolytic intermediates - fructose6P, glyceraldehyde3P

Question 9

Answer 9

Question 10

What is beriberi and how can it be diagnosed?

Answer 10

Beriberi is a disorder caused by thiamine deficiency. A thiamine deficiency can be detected by monitoring transketolase activity in RBCs. If thiamine levels are low, transketolase activity will be decreased.

Question 11

How does the PPP affect nucleotide biosynthesis?

Answer 11

Ribulose5P (from the oxidative phase of the PPP) can be converted into ribose5P via isomerization. Ribose5P is required for nucleotide biosynthesis.

Question 12

What are the most common uses of NADPH?

Answer 12

Question 13

Describe the most prominent way that WBCs use NADPH.

Answer 13

Question 14

What is and what causes chronic granulomatous disease?

Answer 14

Chronic granulomatous disease is caused by a NADPH oxidase deficiency. This cause a defect in WBC respiratory burst diminishing WBC ability to kill bacterium. CGD is characterized by severe and persistent infections.

Question 15

Describe the most prominent way that RBCs use NADPH.

Answer 15

Question 16

What can occur if there is a defect in the PPP in RBCs? Why does this occur?

Answer 16

RBCs utilize NADPH to detoxify H2O2. A deficiency of NADPH, caused by a PPP deficiency, would result in an accumulation of H2O2 that can cause damage to the RBC membrane resulting in hemolysis.

Question 17

How does a G6PD deficiency inherit? In what populations is it most prevalent?

Answer 17

Question 18

What more serious condition does a G6PD deficiency lead to? How?

Answer 18

Hemolytic anemia

1. Diminished G6PD activity results in decreased NADPH production from the PPP
2. This leads to a decrease in the amount of reduced GSH
3. This leads to an increase in RBC H2O2
4. This leads to the damage of fatty acids containing double bonds (cell membrane phospholipids).
5. Eventual hemolysis and development of hemolytic anemia

Question 19

What are Heinz bodies and what typically causes them?

Answer 19

Question 20

T/F - G6PD deficiency only affects RBCs. Explain why

Answer 20

Question 21

Which RBCs are most affected by G6PD deficiency and why?

Answer 21

Question 22

What increases the oxidative stress placed on the body?

Answer 22

Question 23

Why are people from the Mediterranean disproportionately affected by G6PD deficiency?

Answer 23

Many people with G6PD deficiency still produce enough G6PD to avoid expressing symptoms. The mediterranean diet is high in fava beans which places a much larger oxidative stress on the RBCs leading to hemolytic anemia