module 4- Pentose Phosphate Pathway

Question 1

what does the PPP yield?

Answer 1

1 NADPH & ribuose 5-P

Question 2

how is the PPP primarily regulated?

Answer 2

by the cytosolic concentration of NADP+

Question 3

what pathway is coordinately regulated with the PPP?

Answer 3

PPP & glycolysis

Question 4

what enzyme ties the PPP & glycolysis together?

Answer 4

glucose 6-P

Question 5

where is the PPP carried out?

Answer 5

cytosol of tissues

Question 6

plants vs animals synthesis of NADPH

Answer 6

plants- via photosynthesis
animals- via PPP

Question 7

T or F: PPP has an oxidative phase & non-oxidative phase

Answer 7

T

Question 8

what phase # is the oxidative phase

Answer 8

phase 1

Question 9

what happens in phase 1 of PPP (what is oxidized & what is reduced)

Answer 9

glucose 6-P is oxidized and NADP is reduced to NADPH

Question 10

what phase # is the non-oxidative phase

Answer 10

phase 2

Question 11

what happens in phase 2?

Answer 11

ribulose 5-P is converted to ribose 5-P

Question 12

what allows excessive 5-carbon sugars to be converted into intermediates of glycolysis

Answer 12

interconversions

Question 13

how are glycolysis & PPP connected?

Answer 13

shared intermediates- primarily glucose 6-P

Question 14

T or F: need for NADPH is greater than need for ribose 5-P

Answer 14

T

Question 15

how many NADPH are produced per 1 glucose 6-P molecule?

Answer 15

2 NADPH per 1 glucose 6-P molecule

Question 16

is NADPH formed in phase 2?

Answer 16

no, this is where ribulose 5-P is converted to ribose 5-P

Question 17

what enzyme catalyzes ribulose 5-P -> ribose 5-P

Answer 17

isomerase

Question 18

what enzyme catalyzes conversion of ribulose 5-P to xylulose 5-P

Answer 18

epimerase

Question 19

what kind of reactions (reversible/irreversible) do transketolase & transaldolase catalyze?

Answer 19

reversible reactions

Question 20

what molecule does the transketolase reaction produce?

Answer 20

glyceraldehyde 3-P

Question 21

what molecule does the transaldolase reaction produce?

Answer 21

fructose 6-P

Question 22

what enzyme catalyzes phase 1 reaction?

Answer 22

glucose 6-P dehydrogenase

Question 23

what step # is the rate limiting / point of regulation of PPP?

Answer 23

1st step - where NADPH is produced

Question 24

NADPH is competitive ( ) of NADP+ for binding to glucose 6-P dehydrogenase

Answer 24

inhibitor

Question 25

high demand for NADPH = (low/high) NADP+ levels = glucose 6-P is metabolized via (glycolysis/PPP)

Answer 25

low, PPP

Question 26

low demand for NADPH = (low/high) NADP+ levels = glucose 6-P is metabolized via (glycolysis/PPP)

Answer 26

high, glycolysis

Question 27

what is the determining factor if glucose 6-P is metabolized via glycolysis or PPP? (3)

Answer 27

NADP+ levels, need for ribose 5-P & ATP

Question 28

PPP modes 1-4: need for NADPH & ribose 5-P

Answer 28

1) ribose 5-P > NADPH
2) ribose 5-P = NADPH
3) NADPH > ribose 5-P
4) NADPH & ATP are required

Question 29

how many ribose 5-P molecules are produced per every NADPH molecule produced in the PPP?

Answer 29

0.5

Question 30

what is the enzyme that catalyzes the 1st committed step in the PPP?

Answer 30

Glucose 6-P dehydrogenase

Question 31

what 3 enzymes are shared between PPP & glycolysis?

Answer 31

glucose 6-P, glyceraldehyde 3-P, fructose 6-P

Question 32

What two enzymes catalyze the reversible interconventions of the various sugars in the PPP?

Answer 32

transketolase & transaldolase

Question 33

every glucose 6-P is oxidized into ( ) CO2 & ( ) NADPH

Answer 33

6, 12

Question 34

what activates phosphorylase b in muscle? and what inhibits?

Answer 34

AMP, ATP & glucose 6-P

Question 35

what inhibits glycogen phosphorylase?

Answer 35

glucose

Question 36

what enzyme converts GPA -> GPB

Answer 36

phosphatase

Question 37

what enzyme converts GPB -> GPA

Answer 37

kinase