Pentose Phosphate Shunt (5)

Question 1

where are shunt enzymes found in the cell?

hint: it is the same place that enzymes for glycolysis are found

Answer 1

the cytosol

Question 2

what are the two final products of the shunt?

Answer 2

NADPH and ribose-5-phosphate

Question 3

are the 1st three steps of the shunt pathway reversible or irreversible?

Answer 3

irreversible

Question 4

are the 2nd three steps of the shunt pathway reversible or irreversible?

Answer 4

reversible

Question 5

at the end of the oxidative phase of the shunt pathway (after the first 3 steps), what are the products?

Answer 5

two NADPH, Ru5P (a pentose) and CO2 is released

Question 6

how many carbon groups can transketolase transfer? how is it able to do this?

Answer 6

has a TPP as a prosthetic group

can transfer 2 carbons

Question 7

what type of “state” is the NAD+ pool maintained at?

Answer 7

at a highly oxidized state

Question 8

what type of “state” is the NADPH pool maintained at?

Answer 8

highly reduced state

Question 9

what is the function of the pentose phosphate pathway in the adrenal gland?

Answer 9

steroid synthesis

Question 10

what is the function of the pentose phosphate pathway in the liver?

Answer 10

cholesterol & fatty acid synthesis

Question 11

what is the function of the pentose phosphate pathway in the adipose tissue?

Answer 11

fatty acid synthesis

Question 12

what is the function of the pentose phosphate pathway in the testes/ovary?

Answer 12

steroid synthesis

Question 13

what is the function of the pentose phosphate pathway in the mammary gland?

Answer 13

fatty acid synthesis

Question 14

what is the function of the pentose phosphate pathway in the small intestine?

Answer 14

detoxify xenobiotics

Question 15

what is the function of the pentose phosphate pathway in the red blood cells?

Answer 15

detoxify ROS

Question 16

what is the consequence to people with a G6PDH deficiency?

Answer 16

experience hemolytic anemia when they take antimalarial drugs

Question 17

what is ribose needed for?

Answer 17

Needed for info storage, energy transfer, oxidative/reduction reactions & enzyme catalysis

Question 18

list the biosynthetic uses for ribose (4)

Answer 18

rna/dna
atp and other energy carrying NTPs
NADH/FAD
CoA

Question 19

if you only desire to get ribose and not NADPH, how will the pathway run?

Answer 19

run the nonoxidative phase of the shunt in reverse starting with F6P and GAP and ending with R5P

Question 20

what does the pathway do if ribose and NADPH are needed?

Answer 20

run just the oxidative phase of the shunt and convert all of the Ru5P produced to R5P

Question 21

where can G6Pase be found in the body?

Answer 21

only the liver (some small amount in the kidney too though)

Question 22

how many of the kinase reactions of glycolysis are irreversible?

Answer 22

3 out of the 4

Question 23

where in the cell can pyruvate carboxylase be found?

Answer 23

ONLY in the mitochondira

Question 24

what are the two only amino acids that cannot contribute to gluconeogenesis?

Answer 24

leucine and lysine

Question 25

if OAA is unable to leave the mitochondria, explain how it is able to exit

Answer 25

it is first reduced to malate.. then it can exit via the mal/asp shutting running in reverse. once it is cystol, it can be converted back to OAA

Question 26

what is the terminology for the amount of O2 consumed in the liver during the rebuilding of muscle glycogen (cori cycle)

Answer 26

the oxygen debt

Question 27

what is the enzyme involved in the first step of the shunt pathway? and what type of reaction is this step

Answer 27

glucose-6-P dehydrogenase

oxidation

Question 28

what is the enzyme involved in the second step of the shunt pathway?and what type of reaction is this step

Answer 28

6-phosphoglucono lactonase

hydrolysis

Question 29

what is the enzyme involved in the third step of the shunt pathway? and what type of reaction is this step

Answer 29

6-phosphogluconate dehydrogenase

oxidation and decarboxylation

Question 30

what is the enzyme involved in the fourth step of the shunt pathway? and what type of reaction is this step

Answer 30

ribulose-5-P isomerase

isomerization

Question 31

what is the enzyme involved in the fifth step of the shunt pathway? and what type of reaction is this step

Answer 31

ribulose-5-P epimerase

epimerization

Question 32

what is the enzyme involved in the sixth step of the shunt pathway? and what type of reaction is this step

Answer 32

transketolase

intermolecular transfer of a C2 unit

Question 33

what is the enzyme involved in the 7th step of the shunt pathway? and what type of reaction is this step

Answer 33

transaldolase

ibntermolecular transfer of a C3 unit

Question 34

what is the enzyme involved in the 8th step of the shunt pathway? and what type of reaction is this step

Answer 34

transketolase

intermolecular transfer of a C2 unit

Question 35

what is the enzyme is involved in bypass III? What rxn it catalyzing?

Answer 35

Glucose 6 phosphatase

G6P -> glucose

Question 36

what is the enzyme involved in bypass II? What rxn is it catalyzing ?

Answer 36

FBPase

FBP->F6P

Question 37

what is the enzyme involved in bypass I? What rxn is it catalyzing?

Answer 37

Pyruvte carboxylase and PEPCK

Pyruvate->PEP

Question 38

which enzyme has biotin covalently bound to it?

Answer 38

pyruvate carboxylase