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Fundamentals of Nutrition > Fatty Acid Metabolism > Flashcards

Fatty Acid Metabolism Flashcards

1
Q

where does synthesis of fatty acids occur?

A

liver, adipose tissues and mammary glands are the main sites

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2
Q

Can all fatty acids be synthesized?

A

All except C18:2 and C18:3

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3
Q

what is the substrate for synthesis of fatty acids?

A

acetyl CoA

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4
Q

What is acetyl CoA carboxylated to? what is this catalyzed by?

A

Malonyl CoA, catalyzed by acetyl CoA carboxylase

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5
Q

the step wise addition of 2- carbon molecules to a growing chain is catalyzed by what?

A

multifunctional enzyme “fatty acid synthase”

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6
Q

what are the steps in synthesis of fatty acids?

A
  1. glucose enters liver cells and is converted to pyruvate (glycolysis)
  2. pyruvate enters the mitochondria and is converted to acetyl- CoA by pyruvate dehydrogenase and to oxaloacetate by pyruvate carboxylase
  3. acetyl-CoA and oxaloacetate condense to form citrate which leaves the mitochondria
  4. in cytosol, citrate is cleaved to oxaloacetate and acetyl-CoA by citrate lyase (requires ATP + induced by insulin)
  5. acetyl CoA is converted by acetyl CoA carboxylase to malonyl CoA
  6. growing fatty acyl chain on the fatty acid synthase complex is elongated, 2-carbons at a time by the addition of the 3-carbon compound malonyl CoA which is decarboxylated
  7. palmitate is converted to other fatty acyl CoAs by elongation and desaturation
  8. the fatty acyl-CoA combines with glycerol-3-p to form triacylglycerols by a pathway in which phosphatidic acid serves as an intermediate
  9. triacylglycerols packaged in VLDL are secreted into blood
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7
Q

which enzyme cleaves citrate to oxaloacetate and acetyl CoA? what does it require?

A

Citrate lyase it uses ATP

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8
Q

which enzyme converts pyruvate to acetyl-CoA?

A

Pyruvate Dehydrogenase

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9
Q

which enzyme converts pyruvate to oxaloacetate?

A

Pyruvate Carboxylase

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10
Q

which enzyme converts Acetyl-CoA to malonyl CoA?

A

Acetyl CoA carboxylase

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11
Q

fatty acid synthase requires _______ to reduce the growing chain

A

NADPH

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12
Q

where does the NADPH come from?

A

from the pentose phosphate pathway

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13
Q

what is the product released by fatty acid synthase complex?

A

Palmitate

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14
Q

fatty acyl CoA combines with what to form triacylglycerols?

A

Glycerol-3-Phosphate

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15
Q

how do triacylglycerols get into the blood?

A

they are packaged in VLDL

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16
Q

what inhibits Fatty acid synthase?

A

Epinephrine, glucagon inhibit PP2A (protein phosphatase 2A)

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17
Q

what reactivates acetyl-CoA carboxylase?

A

Insulin through stimulation of PP2A which reactivates acetyl-CoA carboxylase and citrate stimulates acetyl-CoA carboxylase

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18
Q

What inhibits Acetyl CoA carboxylase?

A

Palmitoyl-CoA

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19
Q

what are the sources of fatty acids?

A
  • de novo synthesis
  • hydrolysis of cellular triglycerides
  • fatty acids from circulation
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20
Q

What pathways synthesizes triglycerides: Fatty acid + ATP –> Fatty acyl CoA + AMP

A

mainly Glycerol-3-phosphate pathway

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21
Q

what mediates fat mobilization?

A

hormone sensitive lipase (HSL)

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22
Q

what process regulates HSL ?

A

phosphorylation-dephosphorylation process

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23
Q

In what state is HSL dephosphorylated by insulin (inactivation)?

A

the fed state

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24
Q

What happens to HSL in the fasting state?

A

HSL is phosphorylated by epinephrine and norepinephrine

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25
Q

HSL changes triacylglycerol to what?

A

triacylglycerol–> glycerol + 3 fatty acids

26
Q

What is another word for catabolism of fatty acids?

A

ß-oxidation

27
Q

where does B-oxidation occur?

A

in the mitochondria to generate energy

28
Q

why do fats generate more energy?

A

because they exist in more reduced form of CHO

29
Q

when is oxidation of fatty acids high? why?

A

During the starvation state due to increased concentrations of fatty acids in blood

30
Q

what is the first step in B-oxidation?

A

synthesis of fatty acyl CoA in the cytosol by fatty acyl CoA synthetase

31
Q

what mediates the transport of fatty acyl CoA into the mitochondria?

A

Carnitine

32
Q

which fatty acids produces more energy? unsaturated fatty acids or saturated fatty acids?

A

Saturated fatty acids produce more energy

33
Q

during what state is acetyl-CoA from B-oxidation, oxidized to CO2 and water in TCA cycle?

A

the well **fed **state

34
Q

what does the liver convert during the starvation state?

A

the liver converts acetyl CoA to ketones (acetoacetate & B-hydroxybutyrate)

35
Q

what are ketone bodies used for?

A

used for fuel source (energy) by extrahepatic tissues (not the liver)

36
Q

which produces more energy: fatty acids or ketone bodies?

A

ketone bodies produce less energy than fatty acids

37
Q

when might a person have high blood concentrations of ketone bodies?

A

diabetes, starvation or very low CHO diet

38
Q

what inhibites carnitine acyl transferase?

A

Malonyl CoA

39
Q

Hypoglycemia (low blood sugar= glucose) _________ lipolysis in some cases ketone body formation

A

STIMULATES

40
Q

HSL is inactivated by what hormone?

A

INSULIN

41
Q

_____ glucose level and ______ insulin level favors lipolysis.

A

**LOW, ** LOW

42
Q

HSL is activated by which hormones?

A

epinephrine and norepinephrine

43
Q

what stimulates synthesis of acetyl CoA?

A

Citrate

44
Q

What is atherosclerosis?

A

it is a degenerative disease of vascular endothelium

45
Q

what happens in atherosclerosis?

A
  • accumulation of cholesterol and cholesterol esters blocks capillaries causing them to tear up,
  • recruitment of immune cells: cytokines, macrophages, monocytes and T lymphocytes accumulate.
  • LDL is uptaken by phagocytic cells and an increased deposition of lipids in blood vessels (fatty plaque)
46
Q

what is associated with a high amount of LDL ?

A

high fat diet + high cholesterol+ cholesterol esters

47
Q

what are the main lipid risk factors for Cardiovascular disease?

A
  • Cholesterol
  • Saturated and Unsaturated fatty acids
  • Trans fatty acids
48
Q

how can risk of CVD be reduced?

A

by maintaining a low LDL : HDL ratio

49
Q

Apo A: Apo B can be a measure of what?

A

Cardiovascular disease risk ApoB= LDL ApoA=HDL

50
Q

What type of fatty acids are HYPOcholesterolemic (low lvls)?

A

Unsaturated fatty acids (double bonds)

51
Q

what type of fatty acids are HYPERcholesterolemic (high lvls)?

A

Saturated fatty acids

52
Q

which fatty acid is neutral?

A

C18:0

53
Q

Plant PUFA are ____ effective than marine PUFA

A

LESS

54
Q

why can saturated fatty acids be associated with a high risk of cardiovascular disease?

A
  • they suppress bile acid excretion
  • increase synthesis of choleserol + LDL
  • reduce uptake of LDL
55
Q

trans fatty acids come from partial hydrolysis of what?

A

Polyunsaturated fatty acids (PUFA)

56
Q

what is the most abundant trans fatty acid?

A

Elaidic acid (C18:1 FA) and isomers

57
Q

trans fatty acids are ______ cholesterolemic

A

HYPER = high levels of cholesterol

58
Q

which one is more detrimental, saturated fatty acids or trans fatty acids?

A

Trans fatty acids

59
Q

Trans is _______ than Cis

A

WORSE

60
Q

as LDL + total cholesterol increases, HDL ________.

A

decreases

Fundamentals of Nutrition (14 decks)

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