Pentose Phosphate Pathway

Question 1

What are the two phases of PPP

Answer 1

1. Oxidative; redox reactions catalized by enzymes called dehydrogenases to produce NADPH
2. Non -oxidative; recycling pathway

Question 2

What are the major products form oxidative phase

Answer 2

1. Ribose 5-phosphate; for nucleotide synthesis

2. 2 NADPH; for biosynthetic reactions and antioxidant reducing power

Question 3

what are the glycolytic intermediates from non oxidative pathway

Answer 3

1. glyceraldehyde 3-phosphate

2. fructose -6-phosphate

Question 4

PPP has no ____production

Answer 4

energy; no ATP

Question 5

PPP is a ____pathway

Answer 5

fermentative; no oxygen

Question 6

The non oxidative pathway takes 1-ribose -5-phosphate and _____phosphate and rearranges back to _____to allow continuation of oxidative phase

Answer 6

1 xylulose 5-phosphate; glucose 6-phosphate

Question 7

NOn oxidative phase is active only in tissues in which ____is needed in high amounts

Answer 7

NADPH

Question 8

Where does PPP occur

Answer 8

All tissues; anywhere that requires a lot of ribose 5-phosphate for new DNA synthesis:-bone marrow, skin, oral and intestinal mucosa, tumors

Question 9

Where is another place that PPP can occur

Answer 9

Anywhere that needs a lot of NADPH:

1. Tissues that are synthesizing fatty acids, cholesterol or steroid hormones - liver, adipose, adrnal cortex
2. Tissues that exposed to high levels of oxygen- erythrocytes, cornea and lens

Question 10

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 _____

Answer 10

6-phosphogluconate (ends in -ate means you have acid; oxidizing glucose to an acid sugar);
NADH; ribulose 5-phosphate.

Question 11

We need NADPH as a reducing agent for oxidative stress because

Answer 11

a lot of it comes from electron transport

Question 12

What is glutathione (GSH)

Answer 12

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.

Question 13

What are the three aa that make up glutathione

Answer 13

glutamate, cysteine, glycine

Question 14

The oxidative phase of PPP has ____steps. 2 involve _____reactions that produce _____

Answer 14

4; dehydrogenase; NADPH

Question 15

The first step is the ____limiting step that forms the first ____.

Answer 15

rate; NADPH

Question 16

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

Answer 16

lactone; NADPH; aldehyde

Question 17

What are the starting points of non oxidative phase

Answer 17

Ribose 5 phosphate and xylulose 5 phosphate

Question 18

What is the intermediate step of non oxidative phase

Answer 18

Rearranging carbons to get intermediates that we can use

Question 19

Xylulose 5-phosphate activates ____which activates PK2 to stimulate glycolysis

Answer 19

protein phosphatase 2A;

Question 20

Which 2 enzymes transfer 2C or 3C ketose units to aldose acceptors

Answer 20

transketolase and transaldolase

Question 21

transketolase requires ____ to transfer 2 C

Answer 21

thiamine

Question 22

Which 2 enzymes are good intermediates to start the PPP pathway for the oxidative phase

Answer 22

1. Fructose 6-phosphate

2. Glyceraldehy 3-phosphate

Question 23

What is Wernicke Korsakoff syndrome

Answer 23

Caused by a mutation in transketolase and severe deficiency in thiamine. It is common in alcoholics due to poor intestinal absorption of the vitamin.

Question 24

High NADPH levels inhibit ____. This serves to make glucose 6-phosphate available for glycolysis.

Answer 24

glucose 6 phosphate dehydrogenase

Question 25

What is the role of NADPH in the RBC

Answer 25

For repair of oxidative damage

Question 26

When free radicals are produced it causes the production of ____ that can damage cell membranes and cause ___

Answer 26

peroxide; hemolysis (lyse) or hemolytic anemia

Question 27

What does glucose 6 phosphate dehydrogenase deficiency cause

Answer 27

decreases intracellular NADPH and GSH

Question 28

G6PDH deficiency protects against

Answer 28

malaria