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Science for Medicine > LIpids > Flashcards

LIpids Flashcards

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1
Q

Which Vitamin is not derived from a lipid?

A

Vitamin C

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2
Q

Describe fatty acids

A

They have polar heads and fatty acids chain tail

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3
Q

Describe Triacylglycerides

A

esters of glycerol and 3 FA

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4
Q

Describe a phospholipid

A

Polar phosphate head and non-polar lipid tail

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5
Q

What is mainly composed of phospholipids?

A

The cell membrane

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6
Q

Describe a glycolipid

A

A lipid with a carbohydrate attached

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7
Q

Describe a steroid

A

Ring like structure

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8
Q

What are unsaturated FA?

A

When there is one or more double bonds meaning they cannot stack correctly and have low mp due to weak intermolecular forces

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9
Q

What are saturated FA?

A

When there are no C=C double bonds meaning they have a high mp due to strong intermolecular forces between them

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10
Q

If a FA had 18 carbon atoms and 0 double bonds what would be its nomenclature?

A

18:0

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11
Q

What is the nomenclature of lipids?

A

Ratio of Carbons:C=C double bonds

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12
Q

What is a good fatty acid?

A

One that is high in polyunsaturated

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13
Q

What is a bad fatty acid?

A

One that is high in saturated fatty acids (clogs up arteries)

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14
Q

What is a very bad fatty acid?

A

A trans fatty acid - one that comes from the hydrogenation of vegetable oils

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15
Q

What is an essential fatty acid?

A

One that cannot be synthesised by the body so must be obtained from our diets

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16
Q

Beyond what double bond can human not introduce beyond?

A

Carbon 9

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17
Q

is TAG charged?

A

No - its is neutral

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18
Q

What is the main dietary lipid?

A

TAG

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19
Q

What is the lipid used for insulation?

A

TAG

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20
Q

What is omega 3 derived from?

A

Linolenic Acid

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21
Q

How many FA groups do phospholipids have?

A

2

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22
Q

Why is a phospholipid known as amphipathic?

A

Because it has both a polar and non-polar part

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23
Q

What are phospholipids a component of?

A

The plasma membrane

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24
Q

Where is the main site of lipid digestion?

A

Small intestine

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25
Q

What enzyme breaks down lipids?

A

Pancreatic lipase

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26
Q

What do bile salts do to lipids?

A

Act as a detergent forming emulsions

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27
Q

What does lipase break TAG down to?

A

Monoacylglycerol and 2FA

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28
Q

What can cross the microvilli?

A

Short and medium FA

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29
Q

What is steatorrhea?

A

Lipid malabsorption

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30
Q

What is steatorrhea cause by?

A

Defects in bile, pancreatic or intestinal function

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31
Q

What does steatorrhea cause?

A

Excess fat in faeces

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32
Q

Once the FA have been absorbed the the small intestine what happens?

A

They are resynthesised back to TAG

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33
Q

What are lipids transported in the blood in?

A

Chylomicrons

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34
Q

Where are chylomicrons released?

A

Into lymph then into the blood stream

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35
Q

Why does bile break down larger fats?

A

To make smaller fragments

Create a larger surface area for lipase enzymes

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36
Q

What happens in the chylomicrons?

A

TAG is hydrolysed to FA and glycerol

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37
Q

What enzyme hydrolyses TAG in the chylomicrons?

A

Lipoprotein lipase

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38
Q

Where do the remnants of the chylomicrons go?

A

To the liver

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39
Q

Where does the glycerol eventually go?

A

Back to the liver to be converted to G-3-P

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40
Q

What is the nature of the core of a lipoprotein?

A

Hydrophobic

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41
Q

What is the nature of the surface of a lipoprotein?

A

Hydrophilic

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42
Q

What does HDL do?

A

Transports cholesterol from tissues to liver

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43
Q

What does LDL do?

A

Transports cholesterol from liver to tissues

44
Q

What do chylomicrons do?

A

Transport TAG from intestine to tissue

45
Q

What does VLDL do?

A

Transport TAG from liver to tissue

46
Q

Can unlimited LDL be taken up by tissues?

A

No only a certain amount can

47
Q

What can too much LDL cause?

A

Athersclerosis

48
Q

How does too much LDL cause atherosclerosis?

A

It wont be taken up by cells
Is deposited in vessels
Forms plaques

49
Q

What are the 3 stages of beta oxidation?

A

Activation
Transport
Degradation

50
Q

Where are FA in beta oxidation activated?

A

In the cytosol

51
Q

What are fatty acids activated to form?

A

Acyl CoA

52
Q

Why can’t Acyl CoA just enter the mitochondria?

A

Too big

53
Q

How does Acyl CoA enter the mitochondria?

A

Carnitine shuttle

54
Q

Describe the carnitine shuttle

A 
Acyl CoA replaces CoA with carnitine
Becomes Acyl carnitine 
Acyl carnitine can enter the mitochondrial matrix
Converted back to Acyl CoA
Carnitine leaves the matrix
55
Q

What can inhibit the carnitine shuttle?

A

Malonyl CoA

56
Q

How many steps does degradation of B oxidation occur in?

A

4

57
Q

What are the 4 steps of degradation in B oxidation?

A

Dehydrogenation
Hydration
Dehydrogenation
Thiolysis

58
Q

What does the 1st dehydrogenation of degradation produce?

A

FADH2

59
Q

What does the 2nd (but 3rd step of degradation) dehydrogenation produce?

A

NADH

60
Q

What is produced in the 4th step of degradation in B oxidation?

A

Acetyl CoA

61
Q

How many ATP is formed from B oxidation?

A

15 ATP

62
Q

Where does the Acetyl CoA from B oxidation enter?

A

The CAC

63
Q

Why can the Acetyl CoA form beta oxidation not be converted back to glucose?

A

Because of the irreversible pyruvate to acetyl CoA step

64
Q

What forms ketone bodies?

A

Excess Acetyl CoA

65
Q

How many Acetyl CoA combine to form Ketone bodies?

A

2

66
Q

What does the brain use as a source of energy?

A

Ketone bodies

67
Q

Where uses ketone bodies as an energy source?

A

Skeletal muscle
Cardiac muscle
Brian

68
Q

Where are ketones formed?

A

In the liver

69
Q

Where can ketones not be used as an energy source?

A

The liver

70
Q

What does excess ketones do to blood pH?

A

Drops the pH as it is acidic

Can lead to coma then death

71
Q

What is the effect of diabetes ketosis?

A

Cells really need glucose
Breakdown fats
Causes an excess of acetyl CoA
Causes an excess of ketones

72
Q

Where does FA synthesis occur?

A

Liver
Lactating mammary gland
Adipose Tissue

73
Q

Where do we get our FA?

A

From our diet

From synthesis of excess carbohydrates and protein

74
Q

Where is acetyl CoA formed?

A

Mitochondria

75
Q

Where are FA formed?

A

Cytosol

76
Q

How is Acetyl CoA shuffled into the cytosol?

A

Using the citrate shuttle

77
Q

What enzymes are required for FA synthesis?

A

Acetyl CoA carboxylase

Fatty Acid Synthase

78
Q

When does the citrate shuttle work?

A

When Citrate conc. is high

Meaning no more Acetyl CoA is needed

79
Q

What enzyme is needed to form malonyl CoA?

A

Acetyl CoA carboxylase

80
Q

What is the committed step in the synthesis of FA?

A

The formation of Malonyl CoA

81
Q

Malonyl CoA stops…. but is needed for….?

A

Stop degradation

But is needed for synthesis

82
Q

What activates Acetyl CoA carboxylase?

A

High conc. of citrate

Insulin

83
Q

What deactivates acetyl CoA carboxylase?

A

High conc. of palmitoyl CoA (the end product)

Glucagon, epinephrine

84
Q

Why does glucagon and epinephrine inhibit acetyl CoA carboxylase?

A

Suggests the body is quickly needing energy- doesn’t want to waste energy synthesising FA

85
Q

What is the first reaction in FA synthesis?

A

Elongation

86
Q

What are the 3 opposite reaction from FA degradation in FA synthesis?

A

Reduction
Dehydration
Reduction

87
Q

What is used instead of NADH in FA synthesis?

A

NADPH

88
Q

How many times is the elongation cycle repeated?

A

6 more times

89
Q

What is the end product of the elongation cycle?

A

Palmityl-ACP

90
Q

What happens after the elongation cycle?

A

The palmityl CoA is cleaved from the ACP

91
Q

Where does the ACP come into play?

A

The intermediates in FA synthesis are covalently linked to this protein

92
Q

How many enzymes is fatty acid synthase composed of?

A

7

93
Q

What is fatty acid synthase the enzyme a good example of?

A

Quaternary structure

94
Q

Where does most of the NADPH for FA synthesis come from?

A

The pentose phosphate pathway

95
Q

Why do FA synthesis and degradation not run at the same time?

A

Why create something to just destroy it again

96
Q

What is cholesterol?

A

The starting material for the synthesis of steroid hormones

97
Q

How many carbons are eicosanoids derived from?

A

20

98
Q

What is cholesterol a component of?

A

The cell membrane

99
Q

Where is cholesterol synthesised mainly?

A

In the liver

100
Q

How do statins work?

A

They interfere with the reductase enzyme to stop cholesterol being made

101
Q

What do statins lower?

A

LDL levels

Risk of developing atherosclerosis

102
Q

What are eicosanoids precursors for?

A

Prostaglandins
Thromboxanes
Leukotrienes

103
Q

What is cholesterol a precursor for?

A

Steroids

104
Q

What cleaves the ACP from the Palmityl CoA?

A

Thioesterase

105
Q

Where does most of the NADP for the synthesis of Palmitoyl-coA come from?

A

Pentose phosphate pathway

106
Q

What is a storage fate after the synthesis of FA?

A

Storage

Science for Medicine (13 decks)

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