pentose phosphate pathway Flashcards
why is it important
route to oxidise glucose to create NADPH
produces pentose sugars which are incorporated into CoA, RNA,RNA, NADH,FAD AND ATP
route to breakdown pentose sugars from the diet
enables the anabolism and catabolism of 7 and 4 carbon containing sugars
which molecule is used in catabolism
NADH
WHICH molecule is used in anabolism
NADPH
what does NADPH do
operates with enzymes that catalyse anabolic reaction and supply the high energy electrons needed to synthesise energy rich biological molecules
what do NADH do
has a role as an intermediate in the reactions
what is the ratio of oxidised NAD to NADH like
high
what is the ratio of oxidised NADP to NADPH like
kept low
which carrier is citrate moved out of the mitochondria from
tricarboxylate carrier
what does the remaining oxalocacetate form in the pyruvate malate cycle
oxaloacetate forms malate via malate dehydrogenase and forms oxidised NAD
this malate can be converted into pyruvate
which enzyme converts malate into pyruvate
NADPH+ linked malate enzyme
what is XS pyruvate converted into
it is reenters into the matrix of the mitochondria and forms oxaloacetate from pyruvate carboxylase
where does the pentose phosphate pathway occur
in the cytosol of the cell
in the liver lactating mammary glands adipose tissue and adrenal cortex and in RBC
what does the PPP cycle produce
ribose 5 phosphate and NADPH
what is the first step of the PPP cycle
oxidative phase
what happens in the oxidative phase
glucose 6 phosphate is dehydrogenated into 6 phosphoglucono delta lactone by the enzyme glucose 6 phosphate dehydrogenase
also forms 1 NADPH and an ester intermediate
where is glucose 6 phosphate dehydrogenase mutation common
in the tropics
what is the second part of the oxidative phase
the ring opening
how does the ring opening of 6phosphogluco delta lactone occur
due to a hydrolyses reaction and the lactonase enzyme which forms 6 phosphogluconate
what is the third step in the oxidative phase
decarboxylation
how does decarboxylation occur in S3 of oxidative phase
6 phosphogluconate is oxidised to form ribulose 5 phosphate via the enzyme 6 phosphogluconate dehydrogenase
and forms 2 NADPH and CO2
why do we have the non oxidative phase
so the intermediates for glycolysis can be formed
what is the process of the non oxidative phase
- isomerisation
this involves xylulose 5 phospahe to be converted into ribulose 5 phosphate( phosphopentose epimersae) and then ribose 5 phosphate ( phosphopentose isomerase)
how is the ppp CYCLE regulated
by the oxidative stage
as the ratio of NADPH and oxidised NADP is important- if oxidised NADP is high then the pathway will begin
how is the non oxidative patheway controlled
we need the cell to determine products of ribose 5 phosphate fructose 6 phosphate and glyceraldehyde 3 phosphate
which tissues use the PPP cycle
adrenal glands the liver adipose tissue testes ovary mammary gland RBC
what does the adrenal gland use the PPP for
steroid synthesis
what does the liver use the PPP for
fatty acid and cholesterol synthesis
what do the testes use the PPP ffor
steroid synthesis
what does adipose tissue use the PPP for
fatty acid synthesis
what do the ovaries use PPP for
steroid synthesis
what do the mammary glands use PPP for
fatty acid synthesis
what do RBC use the ppp CYCLE FOR
MAINTAINENCE OF REDUCED GLUTATHIONE
what are ROS
highly reactive oxygen containing species
give examples of ROS
superoxide anion radical 02-
hydroxyl radical OH
H202 hydrogen peroxide
ROOH inorganic peroxides
what can damage to DNA LEAD TO
CANCERS
PROTEINS WITH LONG HALF LIVES - associated with ageing
damage to lipids csan contibute to arthroscelrosis
what enhances the formation of reactive oxygen species
free iron
whar does NADPH protect cells from
oxidative damage from hydrogen peroxide and superoxide radicals
what does reduced glutathione do
protects the cell by destroying hydrogen peroxide and hydroxyl free radicals
what is the chemical symbol for oxidised glutathione
GSSG
what is the chemical symbol for reduced glutathione
2GSH
DESCRIBE G6PD deficiency
most people are asymptomatic
what do falafels contain
fava beans which contain divicine when ingested the beans lyse releasing free haemoglobin and toxic ingredient
where is malaria prevalent
tropical africa and parts of middle east and south east asia
how is malaria linked to G6PD deficinecy
one malaria parasite is inhibited by G6PD deficient erythrocytes
it is sensitive to oxidative damage and a high level of oxidative stress
what does divicine do
acts as an antimalarial
