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Biochemistry > Biochem Exam 3: Lipid Metabolism > Flashcards

Biochem Exam 3: Lipid Metabolism Flashcards

1
Q

What is a major source of carbon for fatty acid synthesis?

A

Dietary carbohydrates

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2
Q

Where does fatty acid synthesis primarily occur?

A

Liver;

It can also occur in adipose tissue, brain, kidneys, & lactating mammary glands

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3
Q

What is a precursor molecule for fatty acid synthesis?

A

Acetyl CoA

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4
Q

What is phase 1 of FA synthesis?

A

Cytosolic entry of acetyl CoA (made in mitochondria but needed in cytoplasm)

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5
Q

What is phase II of FA synthesis?

A

Generation of Malonyl CoA (acetyl CoA is carboxylase to malonyl CoA)

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6
Q

What is phase III of FA synthesis?

A

Fatty acid chain formation. ( the enzyme fatty acid synthase catalyzes 7 reactions that incorporate acetyl CoA and malonyl CoA into plamitate (C16))

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7
Q

What is the most important phase of FA synthase?

A

Phase II; Rate limiting step

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8
Q

How does acetyl CoA leave the mitochondria?

A

As citrate using the citrate shuttle

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9
Q

What enzyme breaks citrate down into oxaloacetate and acetyl CoA?

A

ATP citrate lyase

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10
Q

What is a positive regulator for ATP citrate lyase?

A

Glucose, insulin

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11
Q

What is a negative regulator for ATP citrate lyase?

A

PUFA, Leptin

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12
Q

How can malate be transported into mitochondria?

A

Malate alpha ketoglutarate transporter or being converted to pyruvate

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13
Q

How is acetyl CoA converted into malonyl CoA?

A

Acetyl CoA carboxylase (ACC)

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14
Q

What cofactor is needed for acetyl CoA carboxylase to function?

A

Biotin (B7)

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15
Q

What does ACC do?

A

Adds a CO2 to acetyl CoA

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16
Q

When ACC is dimeric it is ___________

A

Inactive

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17
Q

When ACC is polymeric it is ____________

A

Active

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18
Q

ACC is positively regulated by:

A

Citrate, insulin

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19
Q

ACC is negatively regulated by:

A

Glucagon, epinephrine, high AMP, palmitate, PUFA

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20
Q

What inhibits carnitine acyltransferase (rate limiting step in FA degradation) ?

A

Malonyl CoA

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21
Q

Where does the reactions of fatty acid synthesis occur ?

A

Fatty acid synthase complex

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22
Q

What is a positive regulator on the fatty acid synthase?

A

Insulin, glucocorticoid hormones

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23
Q

What is a negative regulator of fatty acid synthase?

A

PUFA

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24
Q

What is the FA synthase composed of?

A

2 identical dimers

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25
Q

How many active enzymes does each dimer have in a FA synthase?

A

7 enzymes

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26
Q

How many proteins does a FA synthase dimer carry?

A

1: acyl carrier protein (ACP)

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27
Q

How does the reaction catalyzed by fatty acid synthase organize itself using:
Condensation
Reduction
Dehydration

A
  1. Condensation
  2. Reduction
  3. Dehydration
  4. Reduction
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28
Q

T/F

Gene expression fo the enzymes is induced by low fat, high carb diets

A

True

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29
Q

When ATP citrate lyase is phosphorylated, is it active or inactive?

A

Active

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30
Q

What enzyme does insulin change in ACC to potivitvely regulate it?

A

Protein phosphatase

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31
Q

What enzyme does epinephrine alter to negatively regulate ACC?

A

Protein kinase A

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32
Q

What enzyme does glucagon alter to negatively regulate ACC?

A

Protein kinase A

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33
Q

What enzyme does AMP alter to negatively regulate ACC?

A

AMP kinase (energy sensor)

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34
Q

When ACC is phosphorylated it is active or inactive?

A

Inactive

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35
Q

With FA synthase, the presence of phosphorylated sugars increase or decrease activity?

A

Increase

36
Q

Palmitate converted to longer chain fatty acids in smooth endoplasmic reticulum or mitochondria is known as _____________

A

Elongation

37
Q

Which organ needs longer fatty acids?

A

Brain

38
Q

What is used as a reducing power when synthesizing FA?

A

NADPH

39
Q

The smooth endoplasmic uses ______________ as a carbon donor

A

Malonyl CoA

40
Q

The mitochondria uses ______________ as carbon donor

A

Acetyl CoA

41
Q

The introduction of double bonds in FA is known as ___________

A

Desaturation

42
Q

Desaturation occurs in the SER, uses NADPH and oxygen, catalyzed by _________________

A

Acyl CoA Desaturases

43
Q

Humans have _________ desaturases

A

4 (4,5,6,9)

44
Q

Double bonds between carbons can be introduced inbetween _______, _______, _______, ________

A

4,5,6,9

45
Q

FA cant be synthesized past _______ in humans

A

Carbons 9 & 10

46
Q

Omega 3 and omega 6 are known as _______________. They need to be ingested as the precursors: ____________ & _____________

A

Essential fatty acids

Linoleic Acid & linoleic acids

47
Q

Triacylglycerols (TAGS) contain about _____________ times as much energy as carbs

A

6.75

48
Q

TAG packaged with ________ to form VLDL and secreted into blood

A

Apoproteins

49
Q

Glucose, glycerol, and fatty acids are ______________ for TAG

A

Precursors

50
Q

____________ is used as backbone for TAG synthesis

A

Glycerol-3-phosphate

51
Q

Intestinal enzymes called _________ digest TAGS

A

Lipases

52
Q

Breakdown depends on __________ of fatty acids in TAG

A

Length

53
Q

Suspension into small particles in the aqueous enviroment

A

Emulsification

54
Q

Fats are emulsified by _______ in the small intestines

A

Bile salt

55
Q

T/F

Bile salts are amphipathic

A

True

56
Q

T/F

Emulsification decreases surface area of fats

A

False

It increases

57
Q

What enzyme digest all lengths of FA in TAGs?

A

Pancreatic lipase

58
Q

The biles salts breaks down fats into FFA and _____________

A

2 monoacylglycerol (2MAG)

59
Q

In the synthesis of chylomicrons the FFA and MAGs are condensed to form _______

A

TAG

60
Q

The TAGs are packaged to form _________

A

Lipoprotein called “chylomicrons”

61
Q

Chylomicrons contain:

A

Apoproteins, phospholipids, cholesterol, and fat soluble vitamins

62
Q

A major apoproteins is

A

APO B 48

63
Q

Nascent chylomicrons are released into the ________ then then the blood stream

A

Lymph

64
Q

Nascent chylomicrons secreted by intestinal epithelial cells by ____________

A

Exocytosis

65
Q

Chylomicrons enter the blood via the ________

A

Thoracic duct

66
Q

Accept proteins from HDL within lymph and blood convert into ________________

A

Mature chylomicrons

67
Q

ApoE is found in the _______

A

Liver cells

68
Q

ApoCII is found in the ________

A

Muscle and adipose tissue

69
Q

T/F

Breakdown of TAGS stored in adipose tissue

A

True

70
Q

In fatty acid oxidation, how many phases are there?

A

2

Phase I and phase II

71
Q

In phase I of fatty acid oxidation, what happens?

A

Fatty acid activation

-occurs in cytosol

72
Q

In phase II of fatty Acid oxidation, what happens?

A

Beta-oxidation

-primarily occurs in mitochondrial matrix

73
Q

What are the four steps of beta oxidation of fatty acids?

A
  1. Acyl CoA dehydrogenase (ACAD)
  2. Enoyl CoA hydratase
  3. B hydroxy acyl CoA dehydrogenase
  4. Acyl CoA Acyl transferase (ketothiolase)
74
Q

What is the order of reaction in beta oxidation:
Oxidation
Hydration
Thiolysis

A 
Oxidation 
Hydration
Oxidation
Thiolysis 
(Repeat 7 times)
75
Q

How much ATP does FADH2 generate?

A

1.5 (times 7= 10.5)

76
Q

How much ATP does NADH generate?

A

2.5 (time 7 = 17.5)

77
Q

How much ATP does Acetyl CoA generate?

A

10 (time 8 =80)

78
Q

The net production of ATP from catabolism of palmitic acid is _______

A

106 ATP

79
Q

Odd numbered double bonds in fatty acids are handled by __________

A

Isomerase

80
Q

Even numbered double bonds are handled by ___________ & ___________

A

Isomerase & reductase

81
Q

Odd chains give rise to prpionyl CoA and acetyl coa, propionyl coa is converted to ____________ and then enters the TCA cycle.

A

Succinyl CoA

82
Q

The conversion of propionyl CoA to succinyl CoA requires __________ vitamin

A

B12 (cobalamin)

83
Q

Water soluble and transportable form of acetyl CoA

A

Ketone bodies

84
Q

Acetoacetate
Beta hydroxybutyrate
Acetone
Are all what type of ketone?

A

Acidic

85
Q

In what order do these go for diabetic ketosis?

  • No Glucose
  • blood pH drops
  • coma and death
  • free fatty acids are released
  • ketone bodies formed
  • oAA levels drop
  • CAC slows
A
  1. No glucose
  2. OAA levels drop
  3. CAC slows
  4. Free fatty acids are released
  5. Ketone bodies form
  6. Blood pH drops
  7. Death

Biochemistry (9 decks)

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