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Biochem Take 2. > Essential Fatty Acids, TAG Metabolism and the Carnitine Shuttle. > Flashcards

Essential Fatty Acids, TAG Metabolism and the Carnitine Shuttle. Flashcards

1
Q

What 2 factors about fatty acids will lead to an increase in melting point?

A

Chain length.

Degree of unsaturation (double bonds).

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2
Q

How many carbons and double bonds does palmitate have and what is its melting point?

A

16 carbons.

No double bonds.

63C.

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3
Q

How many carbons and double bonds does stearate have and what is its melting point?

A

18 carbons.

No double bonds.

70C.

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4
Q

How many carbons and double bonds does oleic acid have and what is its melting point?

A

18 carbons.

1 double bond.

13C.

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5
Q

How many carbons and double bonds does linoleic acid have and what is its melting point?

A

18 carbons.

2 double bonds.

-9C.

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6
Q

How many carbons and double bonds does alpha lonoleic acid have and what is its melting point?

A

18 carbons.

3 double bonds.

-17C.

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7
Q

How many carbons and double bonds does arachidonic acid have and what is its melting point?

A

20 carbons.

4 double bond.

-50C.

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8
Q

How many carbons and double bonds does EPA have and what is its melting point?

A

20 carbons.

5 double bonds.

-54C.

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9
Q

How many carbons and double bonds does DHA have and what is its melting point?

A

20 carbons.

6 double bond.

-45 to -50C.

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10
Q

What lipids are usually found at position 1 on the glycerol backbone in phospholipids?

A

Palmitate and stearate.

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11
Q

What is formed when animals introduce a double bond into palmitate and stearate?

A

Palmitoleate and oleate.

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12
Q

What end of a fatty acid will carbon 1 be at?

A

The carboxyl end.

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13
Q

Where can animals introduce double bonds in fatty acids?

A

9 carbons away from the carboxyl end.

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14
Q

What carbons is the double bond placed at when palmitoleate and oleate are formed?

A

Between carbons 9 and 10.

This is written as Δ9.

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15
Q

Can animals place double bonds in fatty acids near the methyl end?

A

No, only 9 carbons away from the carboxyl end.

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16
Q

What kind of double bonds will always be formed by animals?

A

Cis double bonds.

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17
Q

How can animals obtain fatty acids with bonds beyond Δ9?

A

From the diet.

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18
Q

What are essential fatty acids?

A

Fatty acids with bonds beyond Δ9 that are obtained in the diet.

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19
Q

What organisms form essential fatty acids?

A

Plants.

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20
Q

Can animals alter essential fatty acids?

A

They can elongate them but they cannot change the location of the double bond.

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21
Q

How can animals form bonds that are beyond carbon 9 in an essential fatty acid?

A

By elongating the fatty acid.

They can never move the bond.

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22
Q

How is the family of an essential fatty acid is determined?

A

By counting backwards from the methyl end until the 1st double bond is reached.

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23
Q

The methyl end of an essential fatty acid is known as what carbon?

A

The ω carbon.

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24
Q

What determines the family of an essential fatty acid?

A

The number of carbons between the methyl end and the 1st double bond will determine the family.

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25
Q

What family of essential fatty acid is linoleic acid?

A

Omega-6.

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26
Q

What family of essential fatty acid is α linolenic acid

A

Omega-3.

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27
Q

At what end will carbons be added when animals are elongating an essential fatty acid?

A

To the carboxyl end.

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28
Q

Why does the family of essential fatty acid not change after elongation?

A

Because the number of carbons between the methyl end and the 1st double bond does not change.

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29
Q

Can animals introduce any double bonds into an essential fatty acid?

A

They can introduce double bonds between the carboxyl end and Δ9.

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30
Q

If animals introduce double bods to an EFA will it change the family?

A

No because animals introduce them at the carboxyl end and not at the methyl end.

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31
Q

Arachidonic acid is what family of EFA?

A

Omega 6.

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32
Q

Linoleic acid is elongated to form what fatty acid in humans?

A

Arachidonic acid.

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33
Q

What will humans use arachidonic acid for?

A

To make eicosanoids.

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34
Q

How many carbons do eicosanoids have?

A

20 carbons.

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35
Q

Where do we get omega 3 fatty acids from?

A

From fish who get them from the consumption of algae.

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36
Q

How do fish store alpha linolenic acids?

A

As eicosapentaenoic acid, 20:5, (EPA).

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37
Q

How do humans alter EPA when they obtain it from fish?

A

They elongate it to docosahexaenoic acid, 22:6, (DHA).

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38
Q

Where is DHA usually found?

A

In phospholipids in the brain.

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39
Q

DHA is important for what in humans?

A

Brain and retina function.

It will protect against heart disease.

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40
Q

Why are TAGs synthesised?

A

To store free fatty acids so that they do not damage cells

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41
Q

What is the structure of a TAG?

A

A glycerol backbone that is bound to 3 fatty acids.

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42
Q

What group is removed from fatty acids when they are placed into TAGs?

A

The hydroxyl group.

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43
Q

What is the common intermediate that is formed during TAG synthesis?

A

Phosphatidic acid.

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44
Q

How is phosphatidic acid formed?

A

When a glycerol 3-phosphate molecule from glycolysis is combined with 2 fatty acyl CoAs.

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45
Q

What can phosphatidic acid be used to form?

A

Phospholipids, DAGs and TAGs.

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46
Q

Where does TAG synthesis occur?

A

In the liver, intestinal mucosal and fat cells.

47
Q

When does the liver synthesise TAGs?

A

When blood sugar levels are high.

48
Q

What happens to TAGs that are synthesised in the liver?

A

They are placed inside a VLDL transport protein and released into the blood to be delivered to fat cells.

49
Q

What does VLDL stand for?

A

Very low density lipoprotein.

50
Q

What hormone activates TAG synthesis in the liver?

A

Insulin.

51
Q

When are TAGs synthesised in the intestinal mucosal cells?

A

When the intestinal mucosal cells will join a MAG to 2 free fatty acids to form a TAG.

52
Q

TAGs formed in the intestinal mucosal cells are transported in what transport molecule?

A

A chylomicron.

53
Q

When is insulin present in the body?

A

When blood glucose levels are high.

54
Q

Will the TAGs that are stored in adipose tissue ever leave the fat cell?

A

No.

55
Q

Why will TAGs be degraded?

A

To provide energy for the body when glucose levels are low.

56
Q

When will TAGs be degraded?

A

During fasting and in fight or flight scenarios.

57
Q

What enzyme degrades TAGs?

A

Hormone sensitive lipase.

58
Q

When is HSL active?

A

When it is phosphorylated.

59
Q

What activates the phosphorylation of HSL?

A

Epinephrine or low levels of insulin.

60
Q

What is formed when TAGs are broken down?

A

3 free fatty acids and glycerol.

61
Q

What parts of a TAG are used for energy?

A

The fatty acids.

62
Q

What happens to glycerol when it is released from a TAG?

A

It is recycled or excreted.

63
Q

What is the difference in site of synthesis for hormone sensitive lipase and pancreatic lipase?

A

Hormone sensitive lipase = Fat cells.

Pancreatic lipase = Pancreatic cells.

64
Q

What is the difference in site of action for hormone sensitive lipase and pancreatic lipase?

A

Hormone sensitive lipase = Fat cells.

Pancreatic lipase = Lumen of small intestine.

65
Q

What is the difference in mode of action for hormone sensitive lipase and pancreatic lipase?

A

Hormone sensitive lipase = Cleaves TAGs to 3 free fatty acids and glycerol.

Pancreatic lipase = Cleaves TAGs to MAGs and 2 free fatty acids.

66
Q

What is the difference in mode of activation for hormone sensitive lipase and pancreatic lipase?

A

Hormone sensitive lipase = Phosphorylation, low insulin levels, epinephrine and high cortisol.

Pancreatic lipase = Conjugated bile salts and procolipase.

67
Q

Cleaved fatty acids will bound to what in the blood?

A

They will be non-covalently bound to albumin.

68
Q

Where are cleaved fatty acids transported to once they are in the bloodstream?

A

To the liver and other tissues.

69
Q

What happens when cleaved fatty acids arrive at cells from the bloodstream?

A

They will be taken up for beta oxidation.

70
Q

What happens to glycerol that is formed by TAG cleavage during fasting?

A

It will be used by an enzyme to make glycerol 3-phosphate that can be used in gluconeogenesis.

71
Q

What enzyme converts cleaved glycerol to glycerol 3-phosphate in the fasting state?

A

Glycerol kinase.

72
Q

Can gluconeogenesis and beta oxidation occur at the same time?

A

Yes.

73
Q

What gives the liver enough energy to carry out gluconeogenesis?

A

The beta oxidation of fatty acids.

NADH.

ACoA.

74
Q

What is the hearts preferred fuel?

A

Fatty acids.

75
Q

What is done to reduce the detergent characteristics of fatty acids before they are released to give energy to cells?

A

They are converted to fatty acyl CoA and then esterified.

76
Q

What enzyme will activate and esterify free fatty acids?

A

Fatty acyl CoA synthase.

77
Q

What will fatty acyl CoA synthase use as its substrates?

A

A free fatty acid.

ACoA.

ATP.

78
Q

Where will fatty acyl CoA synthase activate and esterify free fatty acids?

A

In the outer mitochondrial membrane.

79
Q

Is the reaction that is catalysed by fatty acyl CoA synthase reversible?

A

No.

It is irreversible.

80
Q

Why is the activation and esterification of fatty acids irreversible?

A

So that free fatty acids cannot be randomly formed as they would damage the cell.

81
Q

The activation and esterification depends on the availability of what molecule?

A

CoA.

82
Q

Where does the CoA used for fatty acid activation come from?

A

The rapid turnover of activated fatty acids mean that CoA can be recycled and re-used for fatty acid activation.

83
Q

What happens to fatty acyl CoA molecules?

A

They can be used for energy.

To create phospholipids or sphingolipids.

They can be re-syntheised as TAGs.

84
Q

What happens when fatty acyl CoA reaches adipose tissue or a cell membrane?

A

They can be esterified and the CoA can be removed and recycled.

85
Q

Can long chain fatty acids enter the inner mitochondrial membrane?

A

No.

86
Q

Where does the beta oxidation of fatty acids occur?

A

In the mitochondrial matrix.

87
Q

What fatty acids can cross the inner mitochondrial membrane?

A

Medium and short chain fatty acids.

88
Q

What is the carnitine shuttle used for?

A

To transport long chain fatty acids across the inner mitochondrial membrane.

89
Q

What organ is the carnitine shuttle particularly important in?

A

The heart.

90
Q

What fatty acid is used to power the heart?

A

Palmitoyl CoA.

91
Q

The oxidation of Palmitoyl CoA will generate how much ATP?

A

131 ATP.

92
Q

How will the heart gain TAGs after a meal?

A

From TAGs that are found in lipoproteins.

93
Q

How will the heart gain TAGs in the fasting state?

A

From the breakdown of TAGs in fat cells.

94
Q

What will the liver use as an energy source during fasting?

A

Only fatty acid oxidation.

95
Q

The NADH and ACoA that are produced in the beta oxidation of fats will are used by the liver for what?

A

As allosteric regulators of gluconeogenesis.

96
Q

What happens if the carnitine shuttle in the liver is inhibited?

A

It will result in severe hyperglycaemia.

97
Q

What happens in step 1 of the carnitine shuttle?

A

Fatty acyl CoAs cross into the intermembranous space and are joined to a carnitine molecule to make fatty acylcarnitine and free CoA.

98
Q

Where are fatty ACoAs synthesised?

A

In the outer membrane of the mitochondria.

99
Q

What enzyme joins fatty acyl CoA and carnitine in the intermembranous space?

A

Carnitine palmitoyl transferase-1.

100
Q

Where is carnitine palmitoyl transferase-1 found?

A

In the intermembranous space bound to the outer membrane.

101
Q

What is the susbtrate of carnitine palmitoyl transferase-1 found?

A

Fatty acyl CoA and carnitine.

102
Q

What is the product of carnitine palmitoyl transferase-1 found?

A

Fatty acylcarnitine and free CoA.

103
Q

What happens in step 2 of the carnitine shuttle?

A

A translocase enzyme takes fatty acylcarnitine across the inner mitochondrial membrane and delivers it into the mitochondrial matrix.

104
Q

What is the translocase enzyme in step 2 of the carnitine shuttle called?

A

Carnitine acyl carnitine translocase.

105
Q

How is free carnitine removed from the matrix?

A

As carnitine acyl carnitine translocase returns to the inter-membranous space it will transport free carnitine out of the matrix.

106
Q

What does carnitine acyl carnitine translocase do?

A

It transports free carnitine into the inter membranous space.

107
Q

What happens in step 3 of the carnitine shuttle?

A

An enzyme uses CoA to form fatty acyl CoA and free carnitine.

108
Q

What enzyme is used in step 3 of the carnitine shuttle to form fatty acyl carnitine and free CoA in the mitochondrial matrix?

A

Carnitine palmitoyl transferase 2 (CPT-2).

109
Q

What will fatty acyl CoA used for when it is in the mitochondrial matrix?

A

Beta oxidation.

110
Q

What is the substrate for CPT-7?

A

Fatty acylcarnitine and free CoA.

111
Q

What is the product for CPT-7?

A

Fatty acyl CoA and free carnitine.

112
Q

What must be inhibited when fatty acids are being synthesised?

A

The carnitine shuttle.

113
Q

What will inhibit the carnitine shuttle?

A

The presence of manolyl CoA in the cytosol.

114
Q

The presence of manolyl CoA in the cytosol will lead to what?

A

Fatty acid synthesis.

Biochem Take 2. (24 decks)

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