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metabolism > cholestrol- triglycerides > Flashcards

cholestrol- triglycerides Flashcards

1
Q

what is an essential component of cell membranes

A

cholesterol

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2
Q

what does cholestrol form

A

bile and steroid hormones

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3
Q

do we need to consume cholestrol

A

no bc ALL cells have the capability to synthesize it

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4
Q

how can the origin of carbon atoms of cholesterol be deduced

A

from tracer experiments with acetate labelled in methyl carbon or carboxyl carbon

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5
Q

what forms meavlonate

A

three acetates

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6
Q

what does mevalonate form

A

phosphorylated 5C isoprene

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7
Q

what forms the 30 c linear squalene

A

six isoprenes

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8
Q

what forms cholesterol in the last step of synthesis

A

squalene cyclizes to form the four rings whic are modified to form cholesterol

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9
Q

where is cholesterol formed

A

in the cytosol

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10
Q

where are ketone bodies formed

A

in the mitochondria

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11
Q

what is similar between cholesterol synthesis and ketone body synthesis

A

the enzymes and reactions

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12
Q

where is acyl CoA derived from for ketone body formatino

A

B oxidation

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13
Q

where is acetyl CoA derived from for cholesterol synthesis

A

from citrate

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14
Q

what forms HMG CoA

A

three acetyl CoA are condensed

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15
Q

what is reduced to form mevalonate

A

HMG CoA

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16
Q

what is HMG CoA a target of

A

cholesterol lowering drugs

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17
Q

another name for cholesterol lowering drugs

A

statins

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18
Q

rate limiting step in cholesterol synthesis

A

HMG CoA reductase

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19
Q

another name for thiolase

A

Acetyl CoA acetyl transferase

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20
Q

where is NADPH dervied from for cholesterol synthesis

A

PPP

21
Q

step 2 of cholesterol synthesis

A

conversion of mevalonate to activated isoprenes

22
Q

how is mevalonate converted to activated isoprenes

A

3 phosphates are transferred stepwise from ATP to mevalonate
decarboxylation and hydrolysis creates a disphosphorylated 5 carbon product (isoprene) with a double bond
isomerization to a second isoprene

23
Q

what is step 3 of cholesterol synthesis

A

formation of squalene

24
Q

how is squalene formed

A

2 isoperenes join head to tail displacing one set of diphosphates forming 10 carbon geranyl pyrophosphate GPP

GPP joins to another isopentyl pyrophosphate to form 15C farnesyl pyrophosphate

two farnesyl pyrophosphates join head to head to form phosphate free squalene

25
Q

what are the 5 modes of regulation of cholesterol synthesis and trasnport

A
  1. covalent modification of HMG CoA reductase
  2. transcriptional regulation of HMG CoA gene
  3. proteolytic degradation of HMG CoA reductase
  4. activation of ACAT which increases esterification for storage
  5. trasncriptional regulatino of LDL receptor
26
Q

how is HMG CoA regulated

A

at the gene expression level

27
Q

what does intracellular cholesterol concentration regulate

A

cholesterol synthesis

28
Q

what regulates intracellular cholesterol concentration

A

supply of ATP

29
Q

how is short term regulaition of activity of existing HMG CoA reducates regulated by

A

by phosphorylation by the AMP dependent protein kinase AMPK

30
Q

what stimulates phosphorylation of HMG CoA reductase

A

glucagon

31
Q

what promotes dephosphorylatino of HMG CoA reductase

A

insulin

32
Q

what inhibits HMG CoA reductase

A

statins

33
Q

what are the storage molecules for fatty acids

A

TAGS

34
Q

how are TGs carried in circulation

A

in lipoprotiens

35
Q

what is the TG structure

A

glycerol with 3 esterified FA

36
Q

what kind of reaction is addition of 3 FA to glycerol

A

dehydration where water is generation with the addition of each FA

37
Q

what needs to be done to FA before addition to glycerol

A

need to be activated by addition of CoA to carboxyl end like FA synthesis

38
Q

what is required for TG synthesis

A

-glycerol OR DHAP
-NADH
-activated FA
-ATP
-5 enzymes

39
Q

how is DHAP formed

A

glycolysis and glyconeogenesis

40
Q

what is the backbone for TG

A

glycerol 3 phosphate

41
Q

where do most glycerol 3 phosphates come from

A

DHAP from glycolysis or glyconeogeneis via glycerol 3 phosphate dehydrogenase

42
Q

what is the other way of making glycerol 3 phosphate

A

glycerol kinase which is the minor pathway in the liver and kidney

43
Q

synthesis of what occurs before TGs

A

phosphatidic acid

44
Q

what is the precursor of TG

A

phsophatidic acid

45
Q

what is phosphatidic acid made from

A

glycerol 3 phosphate

46
Q

what is phosphatidic acdi

A

uses glyecreol 3 phsophate backbone and the FA are attatched by acyl transferases and CoA is released

47
Q

what is the advantage of making phosphatidic acid

A

it can be made into Triacylglycerols or phospholipid

48
Q

what does phosphatidic acid phosphatase do

A

removes 3 phosphate from the phosphatidic acid yielding 1,2- diacylglycerol

the third carbon is acylated with a third FA yielding TAG not by phosphatidic acid phosphatase

metabolism (14 decks)

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