Pentose Phosphate Shunt (5) Flashcards
where are shunt enzymes found in the cell?
hint: it is the same place that enzymes for glycolysis are found
the cytosol
what are the two final products of the shunt?
NADPH and ribose-5-phosphate
are the 1st three steps of the shunt pathway reversible or irreversible?
irreversible
are the 2nd three steps of the shunt pathway reversible or irreversible?
reversible
at the end of the oxidative phase of the shunt pathway (after the first 3 steps), what are the products?
two NADPH, Ru5P (a pentose) and CO2 is released
how many carbon groups can transketolase transfer? how is it able to do this?
has a TPP as a prosthetic group
can transfer 2 carbons
what type of “state” is the NAD+ pool maintained at?
at a highly oxidized state
what type of “state” is the NADPH pool maintained at?
highly reduced state
what is the function of the pentose phosphate pathway in the adrenal gland?
steroid synthesis
what is the function of the pentose phosphate pathway in the liver?
cholesterol & fatty acid synthesis
what is the function of the pentose phosphate pathway in the adipose tissue?
fatty acid synthesis
what is the function of the pentose phosphate pathway in the testes/ovary?
steroid synthesis
what is the function of the pentose phosphate pathway in the mammary gland?
fatty acid synthesis
what is the function of the pentose phosphate pathway in the small intestine?
detoxify xenobiotics
what is the function of the pentose phosphate pathway in the red blood cells?
detoxify ROS
what is the consequence to people with a G6PDH deficiency?
experience hemolytic anemia when they take antimalarial drugs
what is ribose needed for?
Needed for info storage, energy transfer, oxidative/reduction reactions & enzyme catalysis
list the biosynthetic uses for ribose (4)
rna/dna
atp and other energy carrying NTPs
NADH/FAD
CoA
if you only desire to get ribose and not NADPH, how will the pathway run?
run the nonoxidative phase of the shunt in reverse starting with F6P and GAP and ending with R5P
what does the pathway do if ribose and NADPH are needed?
run just the oxidative phase of the shunt and convert all of the Ru5P produced to R5P
where can G6Pase be found in the body?
only the liver (some small amount in the kidney too though)
how many of the kinase reactions of glycolysis are irreversible?
3 out of the 4
where in the cell can pyruvate carboxylase be found?
ONLY in the mitochondira
what are the two only amino acids that cannot contribute to gluconeogenesis?
leucine and lysine
if OAA is unable to leave the mitochondria, explain how it is able to exit
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
what is the terminology for the amount of O2 consumed in the liver during the rebuilding of muscle glycogen (cori cycle)
the oxygen debt
what is the enzyme involved in the first step of the shunt pathway? and what type of reaction is this step
glucose-6-P dehydrogenase
oxidation
what is the enzyme involved in the second step of the shunt pathway?and what type of reaction is this step
6-phosphoglucono lactonase
hydrolysis
what is the enzyme involved in the third step of the shunt pathway? and what type of reaction is this step
6-phosphogluconate dehydrogenase
oxidation and decarboxylation
what is the enzyme involved in the fourth step of the shunt pathway? and what type of reaction is this step
ribulose-5-P isomerase
isomerization
what is the enzyme involved in the fifth step of the shunt pathway? and what type of reaction is this step
ribulose-5-P epimerase
epimerization
what is the enzyme involved in the sixth step of the shunt pathway? and what type of reaction is this step
transketolase
intermolecular transfer of a C2 unit
what is the enzyme involved in the 7th step of the shunt pathway? and what type of reaction is this step
transaldolase
ibntermolecular transfer of a C3 unit
what is the enzyme involved in the 8th step of the shunt pathway? and what type of reaction is this step
transketolase
intermolecular transfer of a C2 unit
what is the enzyme is involved in bypass III? What rxn it catalyzing?
Glucose 6 phosphatase
G6P -> glucose
what is the enzyme involved in bypass II? What rxn is it catalyzing ?
FBPase
FBP->F6P
what is the enzyme involved in bypass I? What rxn is it catalyzing?
Pyruvte carboxylase and PEPCK
Pyruvate->PEP
which enzyme has biotin covalently bound to it?
pyruvate carboxylase
