Pentose Phosphate Pathway

Front 1

what are the 2 phases of pentose phosphate pathway?

Back 1

phase 1 is oxidative
--makes NADPH
--turns glucose 6-phosphate into ribose 5-phosphate

phase 2 non-oxidative
--interconversion of 3,4,5,6 and 7 carbon sugars

Front 2

what is ribose 5-Pi used for?

Back 2

Component of RNA, DNA, ATP, NADH, FAD, Coenzyme A

fatty acid synthesis
cholesterol synthesis
neurotransmitter synthesis

Front 3

What are the 5 carbon sugars used for?

Back 3

nucleotide biosynthese

glycolytic pathway intermediates

Front 4

Where does the pentose phosphate pathway take place?

Back 4

cytoplasm

both pathways

Front 5

How many molecules of NADPH are made in the oxidative phase?

Back 5

2 molecules NADPH

Front 6

what is the enzyme that catalyzes the conversion of glucose 6-pi to 6-phosphoglucono-d-lactone?

Back 6

glucose 6-Pi dehydrogenase

Front 7

what is the amount that the Km for NAD+ over NADP+ is for glucose 6-Pi dehydrogenase?

Back 7

~1,000 times higher than NADP+

that means glucose-6Pi dehydrogenase is way specific for NADP+

Front 8

Name the structures and the enzyme involved in this reaction

Back 8

Structure 1 glucose 6 phosphate

enzyme is glucose 6-phosphate dehydrogenase

structure 2 is 6-phosphoglucono-b-lactone

Front 9

what is the enzyme that converts 6-Phosphoglucono-b-lactone into 6-phosphogluconate?

Back 9

lactonase

Front 10

Name the structures and the enzyme

Back 10

6-Phosphglucono-b-lactone

lactonase

6-phosphogluconate

Front 11

what enzyme catalyzes the production of a 2nd NADPH from 6-Phosphogluconate?

What's end result?

Back 11

6-phosphogluconate dehydrogenase

ribulose 5-Pi

Front 12

What does phosphopentose isomerase do?

Back 12

ribulose 5-Pi turns into ribose 5-Pi

Front 13

What does phosphopentose epimerase do?

Back 13

ribulose 5-Pi turns into xylulose 5-Pi

Front 14

name the structures and the enzyme

What does phosphopentose isomerase and epimerase do to the product?

Back 14

6-phosphogluconate

6-phosphogluconate dehydrogenase

ribulose 5-Pi

isomerase makes ribose 5-Pi

epimerase makes xylulose 5-Pi

Front 15

what is the net result of the oxidative phase of pentose phosphate pathway?

Back 15

for every glucose 6-Pi
2 NADPH are made + 1 ribose 5-Pi

Front 16

which is more needed in the cells for biosynthesis, ribose 5-Pi or NADPH?

And what happens to the one we don't need as much?

Back 16

NADPH

ribose 5-Pi is converted to GAP-3 and fructose 6-Pi via transketolase and transaldolase

Front 17

what's the net result of transketolase and transaldolase reactions with ribose 5-Pi?

Back 17

3 C5 <------> 2 C6 + C3

3 pentoses go to 2 hexoses and 1 triose

Front 18

How are the pentose phosphate pathway and glycolysis linked?

Back 18

Ribose 5-Pi is converted to GAP-3 via transketolase

C5 + C5 <------> C3 + C7

Front 19

What is the first transketolase reaction?

Back 19

xylulose 5-Pi + ribose 5-Pi <----> GAP-3 + sedoheptulose 7-Pi

Front 20

What reaction does transaldolase catalyze?

Back 20

GAP-3 + sedoheptulose 7-Pi <---> fructose 6-Pi and erythrose 4-Pi

C3 + C7 <----> C6 + C4

Front 21

How is GAP-3 synthesized from erythrose 4-Pi and xylulose 5-Pi?

Back 21

a second transketolase reaction

C4 + C5 <----> C3 + C6

Front 22

If you have 3 ribose 5-Pi how many fructose 6-Pi and GAP-3 will you get?

Back 22

2 fructose-6-Pi and 1 GAP-3

Front 23

What is TPP?

Back 23

thiamine pyrophosphate

accepts anion and releases aldose product which then condenses with 2-carbon glycoaldehyde unit to make a new ketose product

Front 24

which residue on the Schiff base reacts with the ketose substrate?

Back 24

Lys

Front 25

How is the processing of whether or not Glucose 6-Pi goes to glycolysis or pentose phosphate pathway managed?

Back 25

cytoplasmic concentration of NADP+ determines which route Glucose 6-Pi takes

Front 26

Why is NADP+ a regulator in determining the fate of glucose 6-Pi?

Back 26

it is the electron acceptor in pentose phosphate pathway so low levels of NADP+ in cytoplasm inhibits the dehydronation of Glucose-6-Pi.

Front 27

How do excess amounts of NADPH inhibit the pentose phosphate pathway?

Back 27

NADPH competes with NADP+ for the enzyme glucose 6-phospate dehydrogenase so when levels of NADPH are high it ensures we don't shuttle more glucose 6-pi to that pathway.

Front 28

how is regulation of non-oxidative phase of penthose phosphate pathway controlled?

Back 28

based on the availability of the substrates.

The main regulatory and rate determining step is the first one of NADP+ levels.

Front 29

What's going to happen to Glucose 6-Pi if the body is sythesizing alot of nucleotide precursors of DNA in rapidly dividing cells?

Back 29

It needs much more ribose 5-Pi than NADPH.

Glucose 6-Pi will do glycolytic pathway and transaldolase and transketolase will reverse their mechanisms to yield 3 Ribose 5-Pi from 2 fructose 6-Pi and GAP

Front 30

What happens to Glucose 6-Pi if the needs for NADPH and ribose 5-Pi are balanced?

Back 30

Good old fashioned pentose phosphate pathway occurs in which 2 NADPH molecules and 1 ribose-5-Pi are yielded

Front 31

What happens to Glucose -6-Pi if the bod needs to make some serious fatty acids?

Back 31

This requires way more NADPH. The Glucose-6-Pi will all go through the oxidative phase.

Front 32

How does Glucose 6-Pi get fully oxidated?

Back 32

3 reactions. First the normal pentose phosphate pathway yielding 2 NADPH and 1 ribose 5-Pi

The ribose 5-pi goes through the transketolase and transaldolase rxns to yield GAP and fructose 6-Pi and those 2 bad boys go through gluconeogenic pathway where it is recycled into Glucose 6-Pi

Front 33

What if your body needs both ATP and NADPH? How does the Glucose-6-Pi get allocated?

Back 33

After you do the pentose phosphate pathway, the ribose-5-Pi can be turned into pyruvate

Front 34

What is the role of GSH?

Back 34

reduced glutathione inhibits oxidative stress from oxidative metabolism

GSH becomes GSSG and then GSSG is reduced by NADPH

Front 35

Explain why low levels of glucose 6-Pi dehydrogenase would be bad from a ROS standpoint.

Back 35

glucose 6-Pi dehydrogenase is the rate-limiting enzyme involved in manufacturing NADPH in pentose Phosphate pathway.

If there is no NADPH generated because there is none of this enzyme then GSSG remains in its oxidated state and causes cellular damage.

Front 36

name the 3 amino acids in the tripeptide glutathione

Back 36

y-glutamylcysteinylglycine

y-glutamate
cysteine
glycine

Front 37

what does pamaquine treat?

Why does it induce hemolytic anemia in some patients?

Back 37

malaria

It causes hemolytic anemia in patients who have deficiency of glucose6-Pi dehydrogenase because the ratio of GSH is going to be screwy in the cell (because no NADPH to reduce GSSG to GSH) and cells will be prone to hemolysis

Front 38

what is the mechanism reaction about how GSSG gets reduced via glutathione reductase?

Back 38

2 GSH + ROOH----> GSSG + H20 + ROH

Front 39

What does pamaquine generate?

Back 39

peroxides ROOH

Front 40

What are heinz bodies?

Back 40

aggregates on cell plasma membranes of cross-linked Hb

They deform membranes, cause RBC lysis

Front 41

What is the evolutionary advantage of a glucose 6-pi dehydrogenase deficiency?

Back 41

protects against faciparum malaria

11% occurrence in Africans

Perhaps parasites require GSH and pentose phosphate pathway products for growth

Front 42

name structures
enzymes and cofactors produced

Back 42