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Erus-biochemistry > lipid metabolism > Flashcards

lipid metabolism Flashcards

1
Q

substrate for lipid synthesis

A

AcetylCoA

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2
Q

true/false
cholesterol can be converted to acetylcoA

A

false

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3
Q

steps of utilization of fatty acid

A
  1. lipid mobilization
    2.fatty acid activation and transportation to mitochondria
  2. acetylCoA production and TCA cycle
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4
Q

from b-oxidation of palmitate molecule (16C)
total of ____ ATP is formed =
___ FADH2 + ___ NADH + ___ AcetylCoA

A

108 ATP
7 FADH2 + 7 NADH + 8 AcetylCoA

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5
Q

general steps of fatty acid degradation

A
  1. oxidation
    2.hydration
    3.oxidation
    4.cleavage
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6
Q

general steps of fatty acid synthesis

A
  1. condensation
    2.reduction
    3.dehydration
    4.reduction
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7
Q

major fatty acid oxidation is

A

mitochondrial beta oxidation

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8
Q

storage lipids are mobilized by ___

A

hormone sensitive lipase

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9
Q

the enzymes for fatty acid oxidation is located in __

A

mitochondrial matrix

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10
Q

fatty acid is activated by conversion to ___
which is catalyzed by ___ and requires ___

A

fatty acyl-coA
fatty acyl-coA synthetase and inorganic pyrophosphatase

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11
Q

medium and long chain fatty acids are transported across mitochondrial membrane by __

A

carnitine shuttle

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12
Q

steps of carnitine shuttle

A
  1. AcylCoA syntethase produces acylCoA
    2.it diffuses from outer mitochondrial matrix
  2. carnitine palmitoyl-transferase 1 converts acylCoA to acylcarnitine
  3. carnitine acylcarnitine translocase takes acylcarnitine to matrix and releases carnitine
  4. carnitine palmitoyl transferase 2 converts acylcarnitine to acylCoA
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13
Q

___ on outer mitochondrial membrane is the regulatory site of fatty acid catabolism

A

carnitine-palmitoyl transferase 1

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14
Q

in hibernation animals produce water from oxidation of fats during

A

during respiratory electron chain

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15
Q

omega-oxidation occurs in the ___ . It is ___

A

endoplasmic reticulum
subsidiary when b-oxidation is blocked

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16
Q

pathway of microsomal w-oxidation is initiated by ___

A

cytochrome p450 = CYP4A11

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17
Q

enzymes of w-oxidation

A
  1. CYP4A11
    2.alcohol dehydrogenase
  2. aldehyde dehydrogenase
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18
Q

a-oxidation occurs in ___ on __ fatty acids

A

peroxisome
branched FA

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19
Q

enzymes of a-oxidation

A
  1. phytanoil CoA synthetase (ATP)
  2. phytanoyl CoA hydroxylase (a-ketoglutarate)
  3. a-hydroxyphytanoyl CoA lyase
    4.aldehyde dehohydrogenase
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20
Q

final product of a-oxidation is ____ its b-oxidation releases __

A

pristanic acid
propionyl CoA

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21
Q

b-oxidation starts at ___ , the chain is broken between __

A

carboxyl end
2-3 carbons

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22
Q

b oxidation steps

A

palmitoyl CoA – acylCoA dehydrogenase
–> enoyl CoA – enoyl CoA hydratase
–> L-B-hydroxy-acyl-CoA– b-hydroxyacylCoA dehydrogenase
–> b-ketoacyl CoA – thiolase
–> acyl CoA + acetyl CoA

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23
Q

Acyl CoA dehydrogenase is ____ specific

A

chain-length specific

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24
Q

acyl-CoA dehydrogenase is analogous to ___
it is the ___ reaction

A

succinate dehydrogenase
dehydrogenation

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25
Q

enoyl-CoA hydratase is the ___ reaction .
It is analogous to ___ in TCA cycle

A

hydration
fumarase

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26
Q

hydroxyacyl-CoA dehydrogenase uses ___ as the electron acceptor and oxidizes hydroxyl in the __ to a ketone

A

NAD+
C3

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27
Q

when acetyl coA is released by thiolase, the fatty acyl moiety is linked to __

A

cysteine thiol

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28
Q

fatty acyl CoA activation uses ___ ATP

A

2 ATP

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29
Q

metabolic fate of glycerol backbone

A

glycerol – glycerol kinase –> glycerol-3-P
– glycerol-3-P dehydrogenase –> dihydroxyacetone phosphate– triose phosphate isomerase –> D-GA-3P

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30
Q

ketone bodies formation are requirement

A

fatty acid oxidation
lack of oxaloacetate

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31
Q

3 forms of ketone bodies

A

acetone
acetoacetate
b-hydroxybutyrate

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32
Q

steps of ketogenesis

A

2 acetyl-CoA –thiolase –> acetoacetyl CoA
–HMG synthase –> HMG-CoA
–HMG-CoA lyase –> acetoacetate

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33
Q

first product of ketogenesis is __

A

acetoacetate

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34
Q

acetoacetate is converted to acetone by __ and __ is released

A

acetoacetate decarboxylase or spontaneously
CO2

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35
Q

acetoacetate is converted to b-hydroxybutyrate by ___ and ___ is oxidized

A

b-hydroxybutyrate dehydrogenase
NADH

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36
Q

ketogenesis occurs when ___ stores are depleted

A

glycogen

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37
Q

double bonds must be reduced to for oxidation this is achieved by __

A

enoyl CoA isomerase
dienoyl CoA reductase

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38
Q

in odd-nnumbered chain, b-oxidation proceed as usual until left with __

A

propionyl-CoA

39
Q

propionyl CoA conversion to succinyl coA

A

propionyl-CoA carboxylase –> methlmalonylCoA
–methylmalonylCoA epimerase–> methylmalonyl CoA – methylmalonyl-CoA reductase –> succinyl CoA

40
Q

propionyl coa to succinyl coa conversion requires

A

biotin and B12

40
Q

peroxisomes oxidize ___

A

long chain and branched fatty acid

41
Q

fatty acid oxidation stops at ___ in peroxisome

A

octanyl CoA

42
Q

Refsum’s disease

A

defect in degrading branched fatty acids
accumulation of phytanate
due to deficiency in phytanoyl-CoA hydroxylase
phytanic acid is found in plants

43
Q

most common genetic defect in fatty acid oxidation

A

acyl CoA dehydrogenase
hypoglycemia with decreased ketone body formation

44
Q

most common carnitine acyltransferase deficiency

A

carnitine palmitoyltransferase II gene

45
Q

glucagon ___ fatty acid b-oxidation

A

stimulate

46
Q

fatty acid synthesis occurs in ___ inside cell of ___

A

cytoplasm
liver, adipocytes, lactating mammary gland

47
Q

NADPH sources used in fatty acid synthesis

A

malic enzyme
G6PDH
6PGDH
PPP

48
Q

fatty acids are synthesized from ___

A

acetyl CoA

49
Q

the activated donor in fatty acid synthesis is __

A

malonyl-ACP

50
Q

fatty acid synthesis stops at __

A

C16= palmitic acid

51
Q

3 stages of fatty acid synthesis

A
  1. transport of acetyl CoA into cytosol
  2. carboxylation of acetyl CoA
  3. assembly of fatty acid chain
52
Q

addition of 2 carbon units to the growing chain is driven by __

A

decarboxylation of malonyl CoA

53
Q

malonyl CoA production

A

acetyl Coa – acetylCoa carboxylase –> malonyl CoA

54
Q

fatty acid oxidation produces ___ acetyl CoA

A

mitochondrial

55
Q

mitchondrial acetylCoA is transported to cytosol by __

A

linked with oxaloacetate to form citrate
citrate is transported to cytosol which is then converted to acetylCoA and oxaloacetate

56
Q

cofactor requirements of fatty acid

A

NADPH, ATP, Mn2+, biotin, HCO3-

57
Q

committed and irreversible step of lipogenesis

A

carboxylation of acetylCoA to malonyl CoA

58
Q

acetylCoA carboxylase has 2 catalytic activities

A

biotin carboxylase
carboxyltransferase
(biotin carboxyl carrier protein = 3rd subunit)

59
Q

fatty acid synthase complex is a ___dimer. So __

A

homodimer
2 fatty acids synthesized at the same time

60
Q

growing chain of fatty acid is initailly attached to enzyme via __

A

thioester linkage

61
Q

during condensation, growing chain is transferred to ___

A

acyl carrier protein

62
Q

3 steps of condensation reactions

A
  1. acetylcoa added to cys by malonyl/acetylCA ACP transacylase
    2.malonyl added to pant by malonyl/acetylCA ACP transacylase
  2. b-ketoacyl synthase (condensing enzyme) : addition of acetyl group to acetyl on Pant and release with CO2
63
Q

enzymes after condensation

A
  1. b-ketoacyl-ACP reductase
    5.b-hydroxyacyl-ACP dehydratase
    6.enoyl-ACP reductase
    7.condensing enzyme (transfer to sulphur of cysteine)
64
Q

when fatty acid is 16 C atom long, ___ domain catalyzes hydrolysis of thioester bond between fatty acid and phoshopantetheine

A

thioesterase

65
Q

net reaction for palmitate synthesis

A

8 AcetylCoA + 14 NADPH + 7H + 7 ATP –> palmitate + 14 NADPH + 8 HSCoA+ 6 H2O + 7 ADP + 7P

66
Q

acetyl carboxylase is stimulated by

A

insulin , citrate

67
Q

acetyl coA carboxylase is inhibited by

A

glucagon, epinephrine, palmitoylCoA, AMP

68
Q

malonyl CoA inhibits ____

A

carnitine acyltransferase
(fa oxidation is inhibited)

69
Q

during reduction in fa synthesis, ___ is oxidized

A

NADPH

70
Q

acetyl Coa forms the ___ carbons of palmitate

A

15-16

71
Q

phosphopantetheine is linked toserine OH of acyl carrier protein via ___. It contains ___ group in its long flexible arm

A

phosphate ester bond
b-mercaptoethylamine

72
Q

___ is the precursor of stearate and longer chain fatty acid

A

palmitate

73
Q

elongation of fatty acid chain occurs in ___

A

ER

74
Q

elongation steps

A

acyl coa + malonyl coA – 3-ketoacyl synthase –>
3-ketoacyl CoA – 3-ketoacylCoA reductase –>
3-hydroxyacyl CoA – 3-hydroxyacylCoA dehydratase –>
3-trans-Enoyl-CoA–2-trans-EnoylCoA reductase –>
Acyl CoA

75
Q

unsaturation reaction is catalyzed by ___ in ___

A

fatty acyl-CoA desaturase
in smooth ER

76
Q

during fatty acyl coA desaturase __ and __ simoultaneously undergo ___ oxidation

A

fatty acid and NADPH
2 electron oxidation

77
Q

4 fatty acyl desaturase enzymes

A

c4,c5,c6,c9

78
Q

basis for nutritional essentiality of linoleic and linolenic acid

A

inability to incorporate double bond beyond c10

79
Q

desaturase system requires __ and resembles ___ system with __

A

O2
electron transport system
cytochrome b5

80
Q

synthesis of cholesterol starts with ___ pathway

A

mevalonate

81
Q

5 steps of biosynthesis of cholesterol

A
  1. synthesis of mevalonate from acetyl Coa
  2. formation of isoprenoid unit from mevalonate by loss of CO2
  3. condensation of 6 isoprenoid units forming squalene
  4. cyclization of squalene –> lanosterol
  5. formation of cholesterol from lanosterol
82
Q

parent steroid

A

lanosterol

83
Q

first cyclic compound in cholesterol biosynthesis

A

lanosterol

84
Q

mevalonate pathway

A

2 acetylCoA –thiolase –>
acetoacetyl CoA – HMG-CoA synthase –>
HMG-CoA –HMG-CoA reductase –>
mevalonate

85
Q

___ enzyme is targeted by statins (cholesterol inhibitors)

A

HMG-CoA reductase

86
Q

___ enzyme is targeted by statins (cholesterol inhibitors)

A

HMG-CoA reductase

87
Q

___ enzyme is targeted by statins (cholesterol inhibitors)

A

HMG-CoA reductase

88
Q

ATP is used in ___ in cholesterol biosynthesis

A

mevalonate kinase
phosphomevalonate kinse
diphosphomevalonate kinase

89
Q

enzyme producing lanosterol

A

oxidosqualene lanosterol cyclase

90
Q

enzyme producing cholesterol

A

c24 reductase
desmosterol –> cholesterol

91
Q

waste products of ketone bodies

A

acetone
via urine or lung

92
Q

conversion of hydroxybutyrate to acetyl-coA

A

hydroxybutyrate –hydroxybutyrate dehydrogenase
–> acetoacetate – b-ketoacyl transferase
–> acetoacetylcoA –thiolase
–> 2 acetyl CoA

Erus-biochemistry (6 decks)

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