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Biochem > Chapter 28 > Flashcards

Chapter 28 Flashcards

1
Q

what induces fatty acid synthesis?

A

insulin

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2
Q

what inhibits fatty acid synthesis?

A

glucagon and epinephrine

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3
Q

where does fatty acid synthesis occur?

A

in the cytoplasm

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4
Q

what is the first stage of fatty acid synthesis?

A

the transfer if acetyl CoA out of the mitochondria into the cytoplasm

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5
Q

what happens when citrate is transported into the cytoplasm?

A

it is cleaved into oxaloacetate

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6
Q

what is the second stage of fatty acid synthesis?

A

activation of acetyl CoA to form malonyl CoA

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7
Q

what is the third stage of fatty acid synthesis?

A

repetitive addition and reduction of two carbons units to synthesize C16 fatty acid

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8
Q

in the third stage of fatty acid, where does synthesize of C16 fatty acid occur?

A

an acyl carrier protein, a molecular scaffold

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9
Q

which step of fatty acid synthesis is the reverse of β - oxidation?

A

the third stage (repetitive addition and reduction of two carbons units to synthesize C16 fatty acid)

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10
Q

what does citrate do?

A

it carries acetyl groups from mitochondria to the cytoplasm

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11
Q

where is citrate synthesized?

A

in the mitochondria

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12
Q

what happens to citrate when it reaches the cytoplasm?

A

it is cleaved by ATP-citrate lyase to generate acetyl CoA for fatty acid synthesis

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13
Q

what is generated from the cleavage of citrate in the cytoplasm?

A

acetyl CoA for fatty acid synthesis

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14
Q

what is needed for fatty acid synthesis?

A

NADPH

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15
Q

what is the committed step in fatty acid synthesis?

A

the formation of malonyl CoA

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16
Q

what regulates the synthesis of fatty acids?

A

synthesis of malonyl CoA

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17
Q

how is malonyl CoA synthesized?

A

by acetyl CoA carboxylase, an allosteric enzyme

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18
Q

what enzyme catalyzes the formation of fatty acids?

A

fatty acid synthase

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19
Q

where does fatty acid synthesis occur?

A

on the acyl carrier protein (ACP)

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20
Q

what is the acyl carrier protein (ACP)?

A

a polypeptide linked to CoA

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21
Q

what are the 4 steps of fatty acid synthesis?

A
  1. condensation
  2. reduction
  3. dehydration
  4. reduction
22
Q

fatty acid synthesis is always…

A

reducing

23
Q

how does fatty acid synthesis store energy?

A

in the form of electrons

every 2 carbons, electrons are added

24
Q

what sequence is repeated during fatty acid synthesis?

A

reduction, dehydration, reduction

25
Q

what is condensed during fatty acid synthesis?

A

malonyl CoA with butyryl ACP

26
Q

what are the limitations of fatty acid synthase?

A

fatty acid synthase cannot generate fatty acids longer than C16 palmitate

27
Q

how do enzymes extend palmitate?

A

by adding two carbon units, using malonyl CoA as a substrate

28
Q

how are double bonds introduced into saturated fatty acids?

A

by enzymes bound to the endoplasmic reticulum

29
Q

what is the structure of arachidonate?

A

a 20-carbon fatty acid with four double bonds, derived from linoleate

30
Q

what is arachidonate?

A

a precursor for a variety of signal molecules 20 carbons long (eicosanoids)

31
Q

what does arachidonate leads to?

A

prostaglandins

32
Q

what are examples of local acting agents?

A

prostaglandins and other eicosanoids

33
Q

what do local acting agents do?

A

they are short-lived agents that alter activities of cells that synthesize them or are close by

they bind membrane receptors

34
Q

what are the functions of prostaglandins and eicosanoids?

A

stimulate inflammation

regulate blood flow to organs

control ion transport across membranes

modulate synaptic transmission and induce sleep

35
Q

in general, how is fatty acid synthesis regulation?

A
  1. switched off by phosphorylation switched on by Dephosphorylation
  2. allosterically stimulated by citrate
  3. insulin stimulates
  4. glucagon and epinephrine inhibit
36
Q

what is the committed/irreversible step of fatty acid synthesis?

A

conversion of Acetyl CoA to Malonyl CoA by Acetyl CoA Carboxylase 1

37
Q

what activates AMPK?

A

AMP

Glucagon

Epinephrine

38
Q

what inhibits AMPK?

A

ATP

Insulin

39
Q

what does citrate do to carboxylase?

A

it partially activates it

40
Q

what inhibits carboxylase?

A

glucagon and epinephrine

41
Q

how do glucagon and epinephrine inhibit carboxylase?

A

by enhancing AMPK activity

42
Q

what stimulates carboxylase?

A

insulin

43
Q

how does insulin stimulate carboxyalase?

A

insulin stimulates the Dephosphorylation and activation of carboxylase

44
Q

what regulates the enzymes of fatty acid synthesis?

A

adaptive control

45
Q

what does the adaptive control of enzymes in fatty acid synthesis mean?

A

if adequate fats are not present in the diet, the synthesis of enzymes required for fatty acid synthesis is enhanced

46
Q

excess ethanol consumption

A
47
Q

what does the pathway for ethanol processing lead to?

A

excess production of NADH

48
Q

what does excess NADH result in?

A

inhibition of gluconeogenesis and fatty acid degradation

enhancement of lactate production

stimulation of fatty acid synthesis

49
Q

what does the inhibition of gluconeogenesis and enhancement of lactate production from excess NADH result in?

A

lactic acidosis

50
Q

what does the inhibition of Fatty acid degradation and stimulation of fatty acid synthesis result in?

A

accumulation of fats in the liver

Biochem (12 decks)

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