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Biochem Loyola > Triacylglycerides Lecture > Flashcards

Triacylglycerides Lecture Flashcards

1
Q

What is the key control enzyme in fatty acid biosynthesis?

A

Acetyl-CoA carboxylase

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2
Q

Is HMG-CoA reductase activated in the fed or fasted state?

A

Fed

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3
Q

What reaction is facilitated by HMG-CoA reductase?

A

Acetyl-CoA to cholesterol

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4
Q

What hormone mobilizes fatty acyl-CoA through carnitine palmitoyltransferase I to turn into acetyl Co-A

A

Epinephrine

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5
Q

Where can HMG-CoA synthase be found in the cell?

A

Only in the mitochondria

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6
Q

What reaction does HMG-CoA synthase facilitate?

A

Acetyl CoA to Ketone Bodies

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7
Q

What reaction does 7-alpha-hydroxylase facilitate?

A

Cholesterol to bile acids

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8
Q

What reaction does ACAT catalyze?

A

Cholesterol to cholesterol ester

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9
Q

Where can Succinyl-CoA transferase not be found?

A

Liver

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10
Q

What reaction does succinyl-CoA transferase facilitate?

A

Ketone bodies to acetyl-CoA

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11
Q

What reaction does Acetyl-CoA carboxylase facilitate?

A

Acetyl-CoA to fatty acyl CoA

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12
Q

What does fatty acyl-CoA convert to in the fed state?

A

triacylglycerols

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13
Q

What is the effect of insulin on acetyl-CoA carboxylase

A

Promotes conversion of acetyl CoA to fatty acyl-CoA

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14
Q

In the fed state, acetyl-CoA will be converted to cholesterol - true or false?

A

True

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15
Q

In the fasting state, acetyl-CoA will be converted to cholesterol - true or false?

A

False, it will be converted to ketone bodies

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16
Q

How do you get TAGs in the bloodstream through the liver?

A

Glucose and other fuels –> Acetyl CoA –> FA –> TAG –> VLDL

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17
Q

How do you get dietary TAGs into the bloodstream?

A

Dietary TAGs in the small intestine will enter chylomicrons which will enter the bloodstream

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18
Q

What enters the muscles during the fed state?

A

Fatty acids, which are oxidized for energy

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19
Q

What enters the adipose tissue during the fed state?

A

Fatty acids, which are then converted to TAGs

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20
Q

How are fatty acids transported during the fed state?

A

As part of TAGs on lipoproteins

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21
Q

How are fatty acids transported during the fasted state?

A

Bound to albumin

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22
Q

What pathway does glycerol go through during the fasted state?

A

gluconeogenesis

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23
Q

What is the fate of ketone bodies during the fasted state?

A

They will enter the CNS and muscle to be oxidized for energy

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24
Q

What is the fate of fatty acids in the liver during the fasted state?

A

FA –> AcCoA –> ketone bodies –ketone bodies in blood stream–> ketone bodies in muscle, other tissues, CNS –> ketone bodies oxidized for energy

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25
Q

What is the reaction to go from acetyl CoA to palmitate?

A

AcCoA + 7 malonyl-CoA + 14 NADPH + 14H+ –> Palmitate + 7 CO2 + 14 NADP + 8 CoA + 6H20

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26
Q

What is the rate limiting enzyme of DeNovo biosynthesis of fatty acids?

A

Acetyl-CoA Carboxylase

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27
Q

What reaction does acetyl-CoA carboxylase facilitate in DeNovo FA biosynthesis

A

1+7 Acetyl-CoA + 7CO2 –> 7 Malonyl-CoA

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28
Q

What enzyme facilitates the decarboxylation and reduction steps of de novo fatty acid synthesis

A

Fatty acid synthase

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29
Q

What are the 5 necessary components of fatty acid biosynthesis

A
  1. Acetyl groups
  2. AcCoA carboxylase
  3. Biotin
  4. Fatty acid synthase complex
  5. NADPH
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30
Q

What transports acetyl groups for fatty acid biosynthesis from mitochondria to the cytoplasm?

A

Citrate

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31
Q

What is the purpose of biotin in the synthesis of FAs

A

carrier molecule of activated CO2

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32
Q

All carbons are derived (ultimately) from _________

A

Acetyl CoA

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33
Q

Where do most acetyl CoAs come from?

A

Carbohydrate metabolism

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34
Q

What are the 3 functions of citrate in regards to FA metabolism?

A
  1. stimulates FA biosynthesis
  2. transports acetyl groups from mitochondria
  3. allosterically activates Acetyl CoA carboxylase
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35
Q

Citrate is the carrier of ________ from the mitochondria to the cytoplasm

A

Acetyl groups

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36
Q

How does Acetyl CoA catalyze the formation of malonyl CoA

A

It adds CO2

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37
Q

What are the effects of citrate on acetyl CoA carboxylase

A

activation

38
Q

What are the effects of insulin on acetyl-CoA carboxylase?

A

activation

39
Q

What are the effects of biotin on acetyl-CoA carboxylase?

A

activation; serves as a cofactor carrying activated CO2

40
Q

What are the effects of palmitoyl CoA on acetyl-CoA carboxylase

A

inhibition

41
Q

What are the effects of glucagon on acetyl-CoA carboxylase?

A

inhibition

42
Q

What are the effects of glucagon on acetyl-CoA carboxylase?

A

inhibition

43
Q

Acetyl-CoA carboxylase catalyzes a reversible reaction - True or false?

A

False, the reaction is irreversible.

44
Q

What are the products and reactants in the reaction catalyzed by Acetyl-CoA carboxylase?

A

Reactants: Acetyl CoA, HCO3-, ATP
Products: Malonyl CoA, H20, ADP, Pi

45
Q

what enzyme produces malonyl CoA?

A

The reaction catalyzed by acetyl-CoA carboxylase

46
Q

What is the only physiological inhibitor of the rate limiting enzyme in fatty acid oxidation?

A

malonyl CoA

47
Q

Malonyl CoA is the key regulator of _________ and _________

A

FA oxidation; ketone body formation

48
Q

What is a short term allosteric activator of acetyl-coA carboxylase?

A

Citrate

49
Q

What is a short term allosteric inhibitor of acetyl-CoA carboxylase?

A

palmitoyl-CoA (long chain fatty acyl CoA, C16-C18) and AMP (via AMPK)

50
Q

What is a short-term hormonal activator of acetyl-CoA carboxylase?

A

insulin (dephosphorylation)

51
Q

What is a short-term hormonal inhibitor of acetyl-CoA carboxylase?

A

Glucagon, epinephrine (promote covalent modification/phosphorylation)

52
Q

What are the long term regulations that increase Acetyl-CoA carboxylase synthesis?

A

High carbohydrate diet, insulin, thyroid hormone, fat free diet

53
Q

What are the long-term regulations that decrease Acetyl-CoA carboxylase synthesis?

A

High fat diet (via low insulin, high glucagon), fasting, glucagon

54
Q

The Fatty Acid Synthase (FAS) complex catalyzes the formation of ___________ from ___________ and ___________.

A

fatty acids (palmitate); 1 acetyl-CoA; 7 malonyl-CoA

55
Q

How many reaction cycles does FAS complex catalyze?

A

7

56
Q

What is the first major step in forming a C16 compound?

A

Condensation

57
Q

What step does acetyltransferase perform?

A

Acetyl CoA –> butyryl acetyl carrier protein + CoA

58
Q

What step does malonyltransferase perform?

A

malonyl CoA –> Malonate + CoA

59
Q

What electron carrier is used in the reduction steps?

A

NADPH

60
Q

What is the starting molecule in fatty acid elongation?

A

butyryl CoA

61
Q

Where in the cell does acetyl CoA carboxylase work?

A

Cytoplasm

62
Q

What are the 6 enzymes of the fatty acid synthase complex

A
  1. acetyl transacylase
  2. malonyl transacylase
  3. ketoacyl carrier protein synthase (acyl-malonyl-ACP-reductase)
  4. Ketoacyl ACP reductase
  5. 3-hydroxyacyl ACP dehydratase
  6. enoyl ACP reductase
63
Q

What is the full reaction catalyzed by acetyl-CoA carboxylase?

A

Acetyl-CoA + HCO3- + ATP –> Malonyl CoA + ADP + Pi + H+

64
Q

What is the full reaction catalyzed by acetyl transacylase?

A

Acetyl-CoA + ACP –> acetyl-ACP + CoA

65
Q

What is the full reaction catalyzed by malonyl transacylase?

A

Malonyl-CoA + ACP –> Malonyl-ACP + CoA

66
Q

What is the full reaction catalyzed by ketoacyl-carrier-protein synthase (Acyl-Malonyl-ACP-reductase)?

A

Acetyl-ACP + malonyl-ACP –> acetoacetyl-ACP + ACP + CO2

67
Q

What is the full reaction catalyzed by ketoacyl-ACP reductase?

A

acetoacetyl-ACP + NADPH + H+ –> D-3-hydroxybutyryl-ACP + NADP+

68
Q

What is the full reaction catalyzed by 3-hydroxyacyl-ACP dehydratase?

A

D-3-hydroxybutyryl-ACP –> Crotonyl-ACP + H20

69
Q

What is the full reaction catalyzed by Enoyl-ACP Reductase?

A

crotonyl-ACP + NADPH + H+ –> butyryl-ACP + NADP+

70
Q

What is the short term allosteric activator of the FAS complex?

A

Fructose-1,6-bisphosphate

71
Q

When would the allosteric activator of the FAS complex be expressed most?

A

When blood glucose concentrations are high

72
Q

What are 2 ways to increase enzyme synthesis to increase FAS complex function?

A
  1. high carbohydrate diet via insulin

2. Fat free diet

73
Q

What are 3 ways to decrease enzyme synthesis to decrease FAS complex function?

A
  1. Glucagon
  2. High fat diet via low insulin and high glucagon
  3. Fasting
74
Q

Why would fasting decrease FAS complex function?

A

Fasting mobilizes fatty acids

75
Q

What do you get if you elongate palmitate?

A

Stearate

76
Q

What do you get if you desaturate palmitate?

A

Palmitoleate

77
Q

What do you get if you desaturate stearate?

A

Oleate

78
Q

What do you get if you desaturate oleate?

A

Linoleate (18:2)

79
Q

What do you get if you desaturate linoleate?

A

Linolenate

80
Q

What do you get if you elongate and desaturate linolenate?

A

Arachidonate

81
Q

What 3 main things are fatty acids ultimately esterified to?

A
  1. Triacylglycerols
  2. Phospholipids
  3. Cholesterols
82
Q

What are the required cofactors for the reaction palmitate –> palmitoyl-CoA?

A

ATP + CoA –> AMP + PPi

83
Q

What does esterification of palmitoyl-CoA result in?

A
  1. acylglycerols - TAGs

2. Cholesterol Esters

84
Q

What does chain elongation/desaturation of palmitoyl-CoA result in?

A

Acyl-CoA

85
Q

What percent of fatty acids mobilized in the fasting state are redeposited in fatty tissue?

A

60%

86
Q

What is endogenous synthesis of TAGs primarily regulated by?

A

substrate availability

87
Q

PPARs (peroxisome proliferator-activated receptors) promote or inhibit TAG deposition?

A

Promote

88
Q

TAGs synthesized in the liver are packaged into _____

A

VLDLs

89
Q

Glycerol-3-phosphate is a precursor for _____

A

TAGs

90
Q

Dietary TAGs and synthesized TAGs are packaged into __________ for transport in the circulation

A

Lipoproteins

91
Q

Dietary TAGs are incorporated into __________

A

Chylomicrons

Biochem Loyola (14 decks)

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