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IBMS SR > pentose phosphate pathway > Flashcards

pentose phosphate pathway Flashcards

1
Q

why is it important

A

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

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2
Q

which molecule is used in catabolism

A

NADH

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3
Q

WHICH molecule is used in anabolism

A

NADPH

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4
Q

what does NADPH do

A

operates with enzymes that catalyse anabolic reaction and supply the high energy electrons needed to synthesise energy rich biological molecules

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5
Q

what do NADH do

A

has a role as an intermediate in the reactions

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6
Q

what is the ratio of oxidised NAD to NADH like

A

high

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7
Q

what is the ratio of oxidised NADP to NADPH like

A

kept low

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8
Q

which carrier is citrate moved out of the mitochondria from

A

tricarboxylate carrier

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9
Q

what does the remaining oxalocacetate form in the pyruvate malate cycle

A

oxaloacetate forms malate via malate dehydrogenase and forms oxidised NAD
this malate can be converted into pyruvate

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10
Q

which enzyme converts malate into pyruvate

A

NADPH+ linked malate enzyme

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11
Q

what is XS pyruvate converted into

A

it is reenters into the matrix of the mitochondria and forms oxaloacetate from pyruvate carboxylase

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12
Q

where does the pentose phosphate pathway occur

A

in the cytosol of the cell

in the liver lactating mammary glands adipose tissue and adrenal cortex and in RBC

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13
Q

what does the PPP cycle produce

A

ribose 5 phosphate and NADPH

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14
Q

what is the first step of the PPP cycle

A

oxidative phase

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15
Q

what happens in the oxidative phase

A

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

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16
Q

where is glucose 6 phosphate dehydrogenase mutation common

A

in the tropics

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17
Q

what is the second part of the oxidative phase

A

the ring opening

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18
Q

how does the ring opening of 6phosphogluco delta lactone occur

A

due to a hydrolyses reaction and the lactonase enzyme which forms 6 phosphogluconate

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19
Q

what is the third step in the oxidative phase

A

decarboxylation

20
Q

how does decarboxylation occur in S3 of oxidative phase

A

6 phosphogluconate is oxidised to form ribulose 5 phosphate via the enzyme 6 phosphogluconate dehydrogenase
and forms 2 NADPH and CO2

21
Q

why do we have the non oxidative phase

A

so the intermediates for glycolysis can be formed

22
Q

what is the process of the non oxidative phase

A
  1. isomerisation
    this involves xylulose 5 phospahe to be converted into ribulose 5 phosphate( phosphopentose epimersae) and then ribose 5 phosphate ( phosphopentose isomerase)
23
Q

how is the ppp CYCLE regulated

A

by the oxidative stage

as the ratio of NADPH and oxidised NADP is important- if oxidised NADP is high then the pathway will begin

24
Q

how is the non oxidative patheway controlled

A

we need the cell to determine products of ribose 5 phosphate fructose 6 phosphate and glyceraldehyde 3 phosphate

25
Q

which tissues use the PPP cycle

A 
adrenal glands 
the liver 
adipose tissue 
testes 
ovary 
mammary gland 
RBC
26
Q

what does the adrenal gland use the PPP for

A

steroid synthesis

27
Q

what does the liver use the PPP for

A

fatty acid and cholesterol synthesis

28
Q

what do the testes use the PPP ffor

A

steroid synthesis

29
Q

what does adipose tissue use the PPP for

A

fatty acid synthesis

30
Q

what do the ovaries use PPP for

A

steroid synthesis

31
Q

what do the mammary glands use PPP for

A

fatty acid synthesis

32
Q

what do RBC use the ppp CYCLE FOR

A

MAINTAINENCE OF REDUCED GLUTATHIONE

33
Q

what are ROS

A

highly reactive oxygen containing species

34
Q

give examples of ROS

A

superoxide anion radical 02-
hydroxyl radical OH
H202 hydrogen peroxide
ROOH inorganic peroxides

35
Q

what can damage to DNA LEAD TO

A

CANCERS
PROTEINS WITH LONG HALF LIVES - associated with ageing
damage to lipids csan contibute to arthroscelrosis

36
Q

what enhances the formation of reactive oxygen species

A

free iron

37
Q

whar does NADPH protect cells from

A

oxidative damage from hydrogen peroxide and superoxide radicals

38
Q

what does reduced glutathione do

A

protects the cell by destroying hydrogen peroxide and hydroxyl free radicals

39
Q

what is the chemical symbol for oxidised glutathione

A

GSSG

40
Q

what is the chemical symbol for reduced glutathione

A

2GSH

41
Q

DESCRIBE G6PD deficiency

A

most people are asymptomatic

42
Q

what do falafels contain

A

fava beans which contain divicine when ingested the beans lyse releasing free haemoglobin and toxic ingredient

43
Q

where is malaria prevalent

A

tropical africa and parts of middle east and south east asia

44
Q

how is malaria linked to G6PD deficinecy

A

one malaria parasite is inhibited by G6PD deficient erythrocytes
it is sensitive to oxidative damage and a high level of oxidative stress

45
Q

what does divicine do

A

acts as an antimalarial

IBMS SR (38 decks)

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