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Biochemistry Post Midterm > Fatty Acid and TAG Metabolism > Flashcards

Fatty Acid and TAG Metabolism Flashcards

1
Q

which two fatty acids cannot synthesize double bonds beyond the 9 Carbon position?

A

linoleic acid

alpha-linolenic acid

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2
Q

How must we obtain linoleic acid and alpha-linolenic acid?

A

from diet

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3
Q

what makes arachidonic acid?

A

linoleic acid

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4
Q

what is the parent of all eicosanoids?

A

arachidonic acid (from linoleic acid)

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5
Q

When is fatty acid synthesis and TAG synthesis most likely to occur?

A

during fed state

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6
Q

what hormone promotes TAG and fatty acid synthesis?

A

insulin

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7
Q

what is the prepretory step in fatty acid synthesis?

A

acetyl CoA is superactivated/prepped by making malonyl CoA

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8
Q

where are the enzymes of FA synthesis located?

A

cytoplasm

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9
Q

what does malic enzyme convert malate directly to?

A

pyruvate and removes CO2 and produces NADPH

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10
Q

what does acetyl CoA carboxylsae (ACC) need?

A

CO2 and biotin

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11
Q

what does citrate do the ACC?

A

activates allosterically (Short term)

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12
Q

what does palmitoyl CoA do to ACC?

A

allosterically inhibits ACC

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13
Q

what does phosphorylation on Ser/Thr residues through AMPK do to ACC?

A

inhibits ACC (hormonally)

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14
Q

what causes phosphorylation of ACC?

A

glucagon / epinepherine

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15
Q

when is ACC active?

A

dephosphorylated form

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16
Q

what does insulin activate to make ACC active?

A

protein phosphatase

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17
Q

FAS takes 1 malonyl CoA and adds how many carbons to it?

A

2

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18
Q

what are the two forms of FAS?

A

dimer (active)

monomer

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19
Q

how much energy is needed to synthesize FA?

A

7 ATP - to prep malonyl CoA

14 NADPHs - elongation steps

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20
Q

what determines the overall rate of FA synthesis?

A

availability of malonyl CoA

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21
Q

what energy source is important during elongation steps?

A

NADPH

22
Q

Every 2 C added in FA synthesis are added in the form of what?

A

malonyl CoA - uses 2 out of the 3 C (1 C gets kicked off)

23
Q

what are the 2 major roles of citrate?

A

allosteric activator of ACC

vehicle by which acetyl coA moves from mitochondria to cytoplasm

24
Q

what moves acetyl CoA from mitochondria to cytoplasm?

A

citrate

25
Q

where does chain elongation and desaturation occur?

A

ER

26
Q

what 3 things do you need for the desaturation of FA?

A
  1. desaturase
  2. cytochrome B5
  3. cytochrome B5 reductase + NADPH
27
Q

what does elongation and desaturation allow us to do?

A

synthesize polysaturated FA from essentail FA

28
Q

what stimulates TAG synthesis from FA?

A

insulin

29
Q

what stimulates glycogen synthesis from glucose?

A

insulin

30
Q

which part of TAGs is essential for its storage?

A

glycerol backbone

31
Q

which tissues have glycerol phosphate?

A

adipose tissue

liver*

32
Q

what are 90% of FA in plasmas as?

A

fatty acid esters (TAGS, cholsteryl esters, phospholipids) in circulating lipoproteins

33
Q

where does unsaturated FA have double bonds?

A

3 C apart

34
Q

what introduces the kinks to unsaturated FA?

A

cis

35
Q

if linoleic acid is not supplied what becomes essential in diet?

A

arachidonic acid

36
Q

what are the precursors of FA synthesis?

A

acetyl CoA (pantothenic acid)
ATP
NADPH
Co2

37
Q

what is a key intermediate between fat and carb metabolism?

A

Acetyl CoA

38
Q

what are the 3 pathways of FA synthesis?

A
  1. synthesis of palmitate from Acetyl CoA
  2. elongation of palmitate
  3. desaturation
39
Q

where is acetyl CoA in mitochondria coming from?

A

oxidation of pyruvate (PDH complex)

40
Q

what does high ATP in the mitochondria inhibit?

A

isocitrate dehydrogenase

41
Q

what is the first committed step of FA synthesis?

A

Acetyl CoA carboxylase (ACC)

42
Q

what is the rate limiting enzyme for FA synthesis?

A

ACC

43
Q

what does the carboxylation of acetyl CoA to form malonyl CoA require as far as energy?

A

1 ATP per malonyl CoA formed!

44
Q

what are long term regulation of ACC that promote FA synthesis?

A

high carb and fat free diets - upregulation, induction

45
Q

what are long term regulation of ACC that decrease FA synthesis?

A

high fat diets, fasting, glucagon - down reg, repression

46
Q

what up regulates the amount of dimeric form of FAS expressed?

A

insulin

47
Q

what are the key regulators of Acetyl CoA carboxylase (ACC)?

A

citrate
palmitoyl CoA/fatty acyl CoA
Insulin
Glucagon/Epinepherine

48
Q

where does FA elongation occur by reversal of Beta oxidation?

A

mitochondria (minor elongation pathway)

49
Q

where is the major elongation pathway taking place?

A

ER

50
Q

what are sites of unsaturation introduced to?

A

fatty acyl CoA desaturases that introduce double bonds to 5,6,9 position

51
Q

what are the essential FA?

A

linoleate
linolenate
*they have unsaturations beyond the 9 carbon

52
Q

what does the synthesis of polyunsaturated FA start with?

A

linolenic acid

Biochemistry Post Midterm (24 decks)

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