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BIOL 3421 - molecular biochem > lipid synthesis: palmitate > Flashcards

lipid synthesis: palmitate Flashcards

1
Q

what is the shorthand name for palmitate

A

16:0

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2
Q

is palmitate saturated or unsaturated

A

saturated

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3
Q

is fatty acid synthesis endergonic or exergonic? what does this mean?

A

endergonic: requires ATP and reduced electron carriers

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4
Q

list 3 locations of high fatty acid synthesis

A

liver tissue, mammary glands, adipose tissue

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5
Q

T or F: fatty acid synthesis and breakdown are perfect opposites of each other

A

false; they are not opposite

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6
Q

describe why FA synthesis and breakdown are not opposites of each other

A

they are different pathways, require different enzymes, occur in different parts of the cell, and only FA synthesis requires malonyl-CoA

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7
Q

where in the cell does FA synthesis take place

A

cytosol

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8
Q

where in the cell does FA breakdown (oxidation) take place

A

mitochondrial matrix

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9
Q

from which two molecules is malonyl-CoA formed

A

acetyl-CoA and bicarbonate

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10
Q

how many carbons is malonyl-CoA

A

3C

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11
Q

how many carbons is acetyl-CoA

A

2C

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12
Q

how many carbons is bicarbonate

A

1C

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13
Q

T or F: the formation of malonyl-CoA from acetyl-CoA and bicarbonate is reversible

A

false; it’s irreversible

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14
Q

which enzyme creates malonyl-CoA from acetyl-CoA and bicarbonate

A

acetyl-CoA carboxylase

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15
Q

what does the formation of malonyl-CoA require

A

ATP

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16
Q

which cofactor does acetyl-CoA carboxylase have

A

biotin

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17
Q

which vitamin is biotin

A

B7

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18
Q

is biotin water soluble or water insoluble

A

water soluble

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19
Q

name the 3 enzyme domains of acetyl-CoA carboxylase

A

biotin carrier protein domain, biotin carboxylase domain, transcarboxylase domain

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20
Q

describe the arrangement of the 3 acetyl-CoA carboxylase domains in animals

A

they’re located on a single polypeptide

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21
Q

where is biotin attached to ACC

A

to the central biotin carrier protein domain

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22
Q

how is biotin attached to the biotin carrier protein domain of ACC

A

via an amide linkage to a lysine side chain

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23
Q

describe malonyl-CoA formation via ACC

A

CO2 from bicarbonate is attached to a nitrogen in the biotin ring in the biotin carboxylase active site. This requires ATP. Second, the carboxylated biotin swings to the transcarboxylase site, where the CO2 is transferred from biotin to acetyl-CoA to make malonyl-CoA. Finally biotin swings back to pick up another CO2 and repeat the process

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24
Q

how many steps is each 2C addition during FA synthesis

A

4 steps

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25
Q

which organism is fatty acid synthase I found in

A

vertebrates

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26
Q

describe the general structure of FASI

A

a single polypeptide chain with active sites on each of 7 domains

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27
Q

how do the domains function in FASI

A

they function as linked but distinct enzymes

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28
Q

T or F: in FASI, there are no intermediates released part way through the process, only the final 16:0 acyl chain

A

true

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29
Q

list the abbreviated versions of the 7 FASI enzymes

A

KS, MAT, DH, ER, KR, ACP, TE

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30
Q

which organisms is FASII found in

A

plants and bacteria

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31
Q

describe the general structure of FASII

A

the 7 enzyme domains are separate

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32
Q

T or F: FASII generates intermediates

A

true

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33
Q

list the names of the 4 steps needed to add 2C onto the malonyl group on ACP

A

condensation, reduction, dehydration, reduction

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34
Q

why do we need to join a 3C malonyl and a 2C acetyl to get a 4C intermediate, instead of just joining two 2C acetyl groups?

A

the decarboxylation of malonyl in step 1 dramatically decreases the free energy, making the reaction thermodynamically favorable

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35
Q

after palmitate is made, where does the first acetyl that was added end up

A

at the methyl end (C15 and C16)

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36
Q

after palmitate is made, where does the last malonyl group that was added end up

A

carboxyl end (C1)

37
Q

before palmitate synthesis occurs, what must happen to the thiol groups of FASI

A

they must be “charged”

38
Q

what is a thiol group

A

SH

39
Q

during charging of the thiol groups, what happens to acetyl-CoA

A

it binds to a thiol group on a cysteine residue in the KS active site. This is done by MAT. Note: the CoA is not attached anymore

40
Q

during charging of the thiol groups, what happens to malonyl-CoA

A

it binds to a thiol group on the ACP active site. This is done by MAT. Note: the CoA is not attached anymore

41
Q

what is ACP called

A

acyl carrier protein

42
Q

ACP has a prosthetic group derived from vitamin ___

A

B5

43
Q

what is the role of ACP

A

acts as an arm that serves as an anchor for FASI

44
Q

what type of domain is KS

A

a synthase domain

45
Q

T or F: FASI will always be attached to ACP

A

true

46
Q

after charging of the thiol groups, which step is next in FA synthesis

A

condensation

47
Q

describe the condensation step of FA synthesis

A

KS catalyzes condensation: 2C acetyl from KS is brought to the malonyl on ACP = 4C intermediate (CO2 from malonyl is displaced)

48
Q

during condensation of FA synthesis, where did the displaced CO2 come from originally

A

bicarbonate

49
Q

after condensation, which step is next during FA synthesis

A

reduction

50
Q

describe the first reduction during FA synthesis

A

KR catalyzes a reduction of the C3 carbonyl group (uses NADPH as an electron donor)
converts double bonded O into an OH

51
Q

after the first reduction, which step is next during FA synthesis

A

dehydration

52
Q

describe dehydration of FA synthesis

A

DH catalyzes dehydration to generate a double bond between C2 and C3

53
Q

after dehydration, which step is next during FA synthesis

A

the second reduction

54
Q

describe the second reduction of FA synthesis

A

ER catalyzes a reduction of the C2 double bond to make it a single bond (NADPH is the electron donor)

55
Q

after the 4 steps of FA synthesis, what molecule do we have and where on FASI is it attached to

A

butyryl-ACP is the final product (4C)

56
Q

T or F: once we have butyryl-ACP (after the first 4 steps of FA synthesis), we can start from the top

A

false; the ACP site is occupied so we need to move it first so the next malonyl can bind to ACP

57
Q

where is butyryl-ACP transferred to after the first 4 steps of FA synthesis

A

KS

58
Q

after butyryl has been moved from ACP to KS, what occurs?

A

just like before, MAT catalyzes the transfer of the malonyl from malonyl-CoA to the thiol group of the now empty ACP

59
Q

with butyryl on KS and malonyl on ACP, describe what occurs during FA synthesis

A

butyryl on KS (4C) mimics the original acetyl group (2C) on KS. The 4 steps can now repeat, the chain growing by 2C every cycle

60
Q

after the first 4 steps of FA synthesis, how many carbons are added to the chain per cycle?

A

2

61
Q

how many cycles does it take to make palmitate

A

7

62
Q

how is palmitate released from KS

A

TE domain releases palmitate via hydrolysis of the thioester bond (uses 1 water)

63
Q

how many malonyl are needed to make palmitate

A

7

64
Q

describe how much of each thing is required to make the 7 malonyl required for 1 palmitate

A

7 acetyl coA, 7 CO2, and 7 ATP needed to make 7 malonyl

65
Q

how many of each molecule is needed to create 1 palmitate (via 7 cycles of ATP synthesis)

A

acetyl-CoA + 7 malonyl-CoA + 14 NADPH + 14H

66
Q

what is the net amount of water leftover after palmitate is made

A

6 H2O

67
Q

after FA synthesis, why do we have 6 water instead of 7?

A

1 molecule of water was required to hydrolyze the thioester bond that was attaching palmitate to KS

68
Q

where does FA synthesis take place in plants

A

stroma of the cholorplast

69
Q

where does FA synthesis take place in eurkaryotes

A

cytosol

70
Q

list the 2 ways the cytoplasm of eukaryotes can generate lots of NADPH needed for FA synthesis

A
  1. pentose phosphate pathway
    2 malic enzyme
71
Q

describe the pentose phosphate pathway

A

glucose-6-phosphate is converted to ribulose 5-phosphate, which also produces 2 NADPH

72
Q

why is the pentose phosphate pathway used in rapidly dividing cells

A

ribose is an end product, so it helps to keep up with the demand for nucleotides

73
Q

describe the malic enzyme pathway

A

malate is converted to pyruvate via the malic enzyme, and 1 NADPH and 1 CO2 are produced

74
Q

where is acetyl-CoA made

A

mitochondrial matrix

75
Q

list 2 ways in which acetyl-CoA is made in the mitochondrial matrix

A

pyruvate oxidation and catabolism of amino acid skeletons

76
Q

T or F: acetyl-CoA is able to leave the mitochondrial matrix

A

false; the mito matrix is impermeable to acteyl-CoA

77
Q

describe how acetyl-CoA can overcome the inability to leave the mito matrix

A

citrate synthase converts acetyl-CoA to citrate by combining it with oxaloacetate. It can then use the citrate shuttle to get citrate out of the mitochondria, and it can reconvert to acetyl-CoA in the cytosol

78
Q

T or F: after the citrate shuttle system, oxaloacetate is able to go back to the mitochondria

A

false; the mitochondria is impermeable to OAA

79
Q

describe the 2 solutions to get OAA back into the mitochondria after the citrate shuttle system

A
  1. reduce OAA to malate via malate dehydrogenase and NADH. Then use the malate shuttle to get malate back to the mito, then reoxidize to get OAA
  2. reduce OAA to malate, then use malate to make NADPH and pyruvate via the malic enzyme (note: 1 CO2 is lost). Pyruvate can return to the matrix and then OAA can be regenerated via carboxylation
80
Q

list 2 inhibitors of acetyl-CoA carboxylase

A

palmitoyl-CoA and glucagon

81
Q

why is palmtioyl-CoA an inhibitor of FA synthesis

A

it’s a downstream product of malonyl-CoA, so when there is lots of it then there isn’t as much malonyl-CoA, so FA synthesis is inhibited

82
Q

why is glucagon an inhibitor of FA synthesis

A

you don’t want to be building fats when you’re hungry

83
Q

list 2 activators of acetyl-CoA carboxylase

A

citrate, insulin

84
Q

why is citrate an activator of FA synthesis

A

it produces acetyl-CoA, so more acetyl-CoA = more FA synthesis

85
Q

why is insulin an activator of FA synthesis

A

you want to be building fats after eating

86
Q

T or F: FA synthesis can be regulated by gene expression

A

true

87
Q

which family of transcription factors regulates expression of genes involved in fat metabolism based on dietary ingestion of lipids

A

PPAR

88
Q

describe the role of PPAR after eating PUFAs

A

PUFAs bind to PPARs and PPARs supress the expression of lipogenic enzymes (so you make less PUFAs)
(eating PUFAs = you make less PUFAs)

89
Q

describe the role of PPAR after eating lipids

A

PPARs activate genes that encode proteins required for proper lipid storage in adipocytes
(eating lipids = you store more lipids)

BIOL 3421 - molecular biochem (20 decks)

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