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metabolism > FA synthesis > Flashcards

FA synthesis Flashcards

1
Q

what are the two preparatory steps of FA synthesis

A

formation of malonyl CoA
binding of acetyl CoA and MalonylCoA to FAS1

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2
Q

what enzyme makes malonyl CoA

A

acetyl CoA carboxylase

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3
Q

what requires two forms of chemical energy

A

Biosynthesis of FA

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4
Q

how is citrate moved to the cytoplasm to make acetyl CoA

A

citrate transporter

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5
Q

how do we get from citrate to acetyl coa

A

citrate lyase transfers acetyl group to CoA

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6
Q

where is NADPH sources from for reduction reactions

A

PPP and malic enzyme

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7
Q

what does the second preparatory step lead to the release of

A

CoA

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8
Q

what do acetyl coa and malonyl coa connect to FAS via

A

thioester linkage

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9
Q

what adds acetyl CoA group onto SH group of ACP

A

MAT

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10
Q

where does MAT move acetyl coa to

A

SH group of ACP

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11
Q

what happens after acetyl coa is moved to ACP

A

it is transfered to SH group of KS

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12
Q

what happens after acetyl coa is moved to KS

A

MAT moves malonyl cao to SH of ACP

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13
Q

what is the last step in preparation for step 1 for FA synthesis

A

MAT moves malonyl cao to SH of ACP

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14
Q

what does ACP contain

A

4’-phosphopantetheine

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15
Q

what is 4’-phosphopentathiene

A

prosthetic group on ACP AND CoA that serves as a flexible arm, tethers FA chain to surface of FAS and carries reaction intermediates from one active site to the next

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16
Q

moving malonyl groups to SH group name

A

esterification

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17
Q

what form of acyl group is on KS

A

activated acyl group

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18
Q

what happens in the first condensation step of FA synthesis

A

activated acyl group and 2C from malonyl CoA undergo condensation to form a acetoacetyl ACP

CO2 leaves and the acyl chain is extended by 2 carbons

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19
Q

what is formed in the second step of FA synthesis- reduction

A

B keto product is reduced to an alcohol

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20
Q

what is the B keto product

A

acetoacetyl ACP

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21
Q

what catalyzes the reduction recation of FA synthesis

A

B ketoacyl-ACP reductase/ KR

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22
Q

what is required for the reduction step of FA synthesis

A

B ketoacyl-ACP reductase/ KR and NADPH as electron donor

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23
Q

what specifically happens to the carbons in the reduction step

A

reduction of carbonyl group at C3 to from D- B- hydroxybutyryl-ACP

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24
Q

what is the third step in FA synthesis

A

dehydration

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25
Q

what enzyme catalyzes the third step in FA synthesis

A

B-hydroxyacyl-ACP dehydratase/ DH

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26
Q

what is formed by step 3 and how

A

trans-delta2-butenoyl-ACP by removing H20 elements from C2 and C3 of b-hydroxybutyryl-ACP

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27
Q

4th step of FA synthesis

A

reduction

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28
Q

what enzyme cataylyzes the 4th step

A

enoyl-ACP reductase/ ER

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29
Q

what does enoyl-ACP reductase/ ER do

A

catalyzes reduction of DB of trans delta2-butenoyl-ACP to form butyryl ACP

30
Q

how do we set up for the next pass of FA synthesis

A

transfer of butyryl group from ACP to KS

recharging ACP with new malonyl COa

31
Q

where is C16 derived from

A

methyl carbon atom of the acetyl Coa used to initially prime the system

32
Q

where is C15 derived from

A

carboxyl carbon atom of the acetyl Coa used to initially prime the system

33
Q

what is 16:0 called

A

palmitate

34
Q

how many cycles of FA (4 steps) does palmitate go throu

A

7

35
Q

what releases palmitate

A

hydrolysis of thioester linkage by thioesterase/ TE

36
Q

what does TE do

A

hydrolizes the thioester linkage

37
Q

what regulates FA synthesis

A

ACC phosphorylation

level of gene expression by AAC and FAS

inhibition of FA synthesis and oxidation occuring together by malonyl CoA

38
Q

how does malonyl coa inhibit futiile cycle

A

inhibits FA import into mitochondria to ultimately shut down B oxidation

39
Q

what does ACC cause

A

polymerization into long inactive fillaments

40
Q

what is the rate limiting step of FA synthesis

A

ACC phosphorylation

41
Q

what is the precursor of long chain saturated FA

A

palmitate

42
Q

FA elongatino systems lengthen…

A

palmitate

43
Q

where does the lengthening of palmitate occur

A

in the smooth ER and mitochondria

44
Q

what is the most common product of lengthening of palmitate occur

A

stearate 18:0

45
Q

what enzyme is required for the desaturation fo FA

A

fatty acyl CoA desaturase

46
Q

what does fatty acyl CoA desaturase do

A

catalyzes oxidative reaction indoducing double bond

47
Q

what does desaturation of FA require

A

NADPH, cyt b5, and cyt b5 reductase

48
Q

what accepts electrons in the desaturation of FA

A

O2 accepts 2 electrons from saturated FA and 2 electrons from cyt b5

49
Q

what desaturases do humans have

A

4,5,6,9 but not beyond 9

50
Q

what can desaturate positions beyond C9

A

plants

51
Q

what are the essential FA

A

linoleate and a linolenate

52
Q

what is linoleate

A

18:2 w-6

53
Q

where are linoleate double bonds

A

9 and 12

54
Q

a linolenate

A

18:3 w3

55
Q

where are a linolenate duoble bonds

A

9,12,15

56
Q

what do PUFAs do

A

help control membrane fluidity

57
Q

where are cholesterols acrbon atoms provided by

A

acetate

58
Q

what is essential intermediate for the pathway of cholesterol synthesis

A

isoprene units

59
Q

what are the stages in cholestrol synthesis

A

condensation

mevalonate to activated isoprene units

polymerization of 6 isoprene units to form 30 carobn linear squalene

cyclization of squalene to from 4 rings of steroid nucleus

60
Q

what are two descriptive words for FA synthesis

A

endergonic and reductive

61
Q

what is ACP recharged with after one round of FA synthesis

A

malonyl CoA

62
Q

what is formed from the reduction step

A

D-B hydroxybutyryl- ACP

63
Q

what does DH stands for

A

D-B hydroxyacyl ACP dehydratase

64
Q

what is formed by the dehydratino step

A

trans delta2 butenoyl ACP

65
Q

how many cycles of FA synthesis did palmitate go through

A

7

66
Q

what activates and inactivates ACC

A

citrate activates it

epinephrine phosphorylation and inactivation
glucagon phosphorylation and inactivation
high [AMP] phoshorylation and inactivation

palmitoyl CoA inactivates it

67
Q

what occurs in smooth ER and mitochondria

A

FA elongation systems

68
Q

where do FA elongation systems happen

A

in mitochondria and smooth ER

69
Q

what enzyme is used for FA desaturation

A

fatty acyl coa desaturase

70
Q

what does FA coa desaturase require

A

NADPH, cytb5, cytb5 reductase

71
Q

role of PUFAs

A

control membrane fluidity

metabolism (14 decks)

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