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unit 6: MCP > fatty acid synthesis (13) > Flashcards

fatty acid synthesis (13) Flashcards

1
Q

what organ are fatty acids synthesized in?

A

the liver

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2
Q

when acetyl coA is in high concentration, what enzyme is inhibited?

A

pyruvate dehydrogenase

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3
Q

what enzyme is inhibited when there are low levels of acetyl coA?

A

pyruvate carboxylase

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4
Q

what enzyme cleaves citrate in the cytosol to acetyl coA and OAA?

A

citrate lyase

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5
Q

where can the enzyme pyruvate dehydrogenase be found (what part of the cell)

A

ONLY in the mitochondria

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6
Q

can acetyl coA cross the mitochondrial membrane?

A

HELLL NO

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7
Q

what are the 2 sources of NADPH that is necessary for the synthesis of fatty acids?

A
  1. recycling of OAA

2. pentose phosphate shunt

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8
Q

what are the two steps of OAA recycling?

A
  • OAA is reduced by an NADH dependent cytosolic malate dehydrogenase to malate
  • Malate is then converted by the NADP+ dependent malic enzyme which oxidizes & decarboxylates malate to pyruvate
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9
Q

what are the two enzymes necessary for fatty acid synthesis?

A

acetyl coA carboxylase-ACC

fatty acid synthase-FAS

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10
Q

which enzyme is the rate controlling step in fatty acid synthesis?

A

ACC

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11
Q

what reaction does ACC catalyze?

A

the addition of a carboxyl group from acetyl coA onto malonyl coA

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12
Q

what is ACC’s cofactor?

A

biotin

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13
Q

what does biotin bind in the presence of ATP during the ACC reaction?

A

binds CO2

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14
Q

list the positive regulators of ACC (2)

A
  • citrate causes ACC to polymerize (activates ACC)

- insulin stimulates phosphatase which dephosphorylates ACC to its active state)

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15
Q

list the negative regulators of ACC (3)

A
  • palmitoyl coA (feedback inhibition)
  • glucagon & epinephrine phosphorylate ACC
  • AMP (indicates low energy levels)
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16
Q

what are the 5 steps of fatty acid synthesis

A
  1. activation
  2. condensation
  3. reduction
  4. dehydration
  5. reduction
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17
Q

what enzyme catalyzes step 1 of fatty acid synthesis?

A

ACC

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18
Q

what enzyme catalyses steps 2-5 of fatty acid synthesis?

A

FAS

19
Q

what enzyme of fatty acid synthesis does this action describe?
“adds two carbon units form malonyl coA to the growing fatty acyl chain with the final product being palmitiate”

A

FAS

20
Q

describe what is happening in the 2nd step of fatty acid synthesis the condensation step

A
  • acetyl group from acetyl coA first associates with the ACP phospho-pantetheinyl sulfhydryl group and then is transferred to the cysteine sulfhydryl of the other subunit
  • malonyl from malonyl coA then associates with ACP phospho-pantetheinyl sulfhydryl group
  • the malonyl and the acetyl groups condense with the release of the malonyl carboxyl group as CO2
21
Q

what is the product of the condensation step, step 2 of fatty acid synthesis?

A

a 4 carbon ß-keto acyl chain which is attached to the ACP phospho-pantetheinyl sulfhydryl group

22
Q

what step does the following describe

“reduction of the beta-keto group to an alcohol”

A

step 3, reduction step

23
Q

what molecule provides the reducing equivalents for steps 3 through 5?

A

NADPH

24
Q

where are fatty acids elongated (within the cell)

A

in the ER

25
Q

what is the major elongation that occurs in the body?

A

palmityl coA to sterayl coA (18 carbons)

26
Q

what is fatty acid desaturatoin?

A

the oxidation of fatty acids resulting in cis double bonds

it creates lipids of increasing structural and functional complexity with distinct biological roles

27
Q

where are desaturases located?

A

in the ER of a cell

28
Q

what 3 things do desaturases require?

A

O2, NADH and cytochrome b5

29
Q

what happens to desaturase activity during starvation?

A

their activity sharply decreases

30
Q

what happens to desaturase activity when large amounts of unsaturated fats are eaten?

A

desaturase activites descrease

31
Q

what 3 distinct desaturases do humans have?

A

∆9 desaturase
∆6 desaturase
∆5 desaturase

32
Q

what type of PUFAs does fish oil contain?

A

ω3 and ω6 PUFAs

33
Q

why isn’t arachidonic acid considered an essential fatty acid?

A

because of linoleic acid is present (which is essential) the body can synthesize it

34
Q

list the 3 things that arachidonic acid is considered a substrate for

A

leukotrines, thromboxanes &prostaglandin

35
Q

name some things that eicosanoids are involved in

A

inflammatory response
smooth muscle contraction
brococonstriction/dilation

36
Q

what are the 3 pathways for eicosanoids syntheiss?

A
  1. cyclic (cyclooxygenase) pathway
  2. linear (lipoxygenase) pathway
  3. cytochrome P450 pathway
37
Q

what does the cytochrome P450 pathway form?

A

epoxides

38
Q

what does the linear pathway form?

A

leukotrines, HETEs and lipoxins from a common intermediate HPETE

39
Q

what does the cyclic pathway form?

A

prostaglandins, throboxanes and prostacyclins

40
Q

what enzyme does aspirin and other NSAIDs act on?

A

COX enzyme

41
Q

what is the function of the COX enzyme?

A

convert arachidonic acid to PGH2

42
Q

COX1 or COX2 which does the following describe

“ the consitiutive form expressed in all tissues”

A

cox1

43
Q

describe cox 2

A

the inducible form regulated by a variety of cytokines and growth factors
increased in response to inflammation

44
Q

which of the following are irreversilbe/reversilbe inhibitors of COX1 and COX2
aspirin
acetaminophren
ibuprofen

A

aspirin- irreversible inhibitor
acetaminophren- reversible inhibitor
ibuprofen- reversible inhibitor

unit 6: MCP (17 decks)

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