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MEH A > Session 2 Lecture 2 > Flashcards

Session 2 Lecture 2 Flashcards

1
Q

Are lipids soluble or insoluble?

A

Insoluble in water (hydrophobic) but are soluble in organic solvents

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2
Q

How many classes of lipids are there?

A

3

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3
Q

What are the different classes of lipids?

A
  • Fatty acid derivatives
  • Hydroxyproline-methyl glutaric acid derivatives
  • Vitamines
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4
Q

Give some examples of fatty acid derivatives

A

Fatty acids
Triacylglycerides
Phospholipids
Eicosanoids

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5
Q

What are fatty acids?

A

Fuel molecules

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6
Q

What are triacylglyerols?

A

Fuel storage and insulation

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7
Q

What are phospholipid function?

A

Component of membrane and plasma lipoproteins

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8
Q

What is eicosanoids function?

A

Local mediators

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9
Q

Give some examples of hydroxyl-methyl acid derivatives

A

Ketone bodies
Cholesterol
Cholesterol esters
Bile acids and salts

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10
Q

What are ketone bodies?

A

Water soluble fuel molecules

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11
Q

What is function of cholesterol?

A

Membrane and steroid hormone synthesis

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12
Q

What is the function of cholesterol esters?

A

Cholesterol storage

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13
Q

What is the function of bile acids and salts?

A

Lipid digestion

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14
Q

What is the major dietary and storage lipid in the body?

A

Triacylglycerols

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15
Q

What is the structure of a triacylglycerol?

A

3 fatty acids esterified to glycerol

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16
Q

Describe some features of triacylglycerols?

A

Triacylglycerols are hydrophobic therefore stored in an anhydrous form.

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17
Q

How are TAGs stored?

A

Adipose tissue

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18
Q

When are TAGs used?

A

Utilised in prolonged exercise, starvation and during pregnancy

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19
Q

What sort of control is the storage of TAGs under?

A

Hormonal control

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20
Q

What is the storage of TAGs promoted by?

A

Insulin

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21
Q

What is storage of TAGs reduced by?

A

Glucagon, adrenaline, cortisol, growth hormone and thyroxine.

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22
Q

What happens when you ingest lipids?

A

The lipid is hydrolysed by pancreatic lipase in the small intestine to glycerol and fatty acids

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23
Q

What does the hydrolysation of lipids require?

A

Bile salts and a protein factor called colipase

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24
Q

What happens to the glycerol from the lipid breakdown?

A

Glycerol enters the blood stream and is transported to the liver where it is metabolised

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25
Q

Describe some features of fatty acids?

A

They are hydrophobic and highly reduced molecules, properties that make them ideal for energy storage

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26
Q

Are saturated fatty acids non essential components of the diet?

A

Yes because they can be synthesised from carbohydrates and certain amino acids

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27
Q

Why are certain polyunsaturated fatty acids essential components of the diet?

A

They can’t be synthesised in the body

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28
Q

Give a n example of an important polyunsaturated fatty acid?

A

Arachidonic acid - it is a starting point for the synthesis of the eicosanoids

29
Q

What are the eicosanoids?

A

They are a family of signalling molecules in the body, including prostaglandins

30
Q

What happens to some of the fatty acids and glycerol in the small intestine?

A

Some is recombined and transported as TAG by chylomicrons and stored as adipose tissue

31
Q

What activated fat metabolism?

A

Stressful situations - aerobic exercise, starvation, lactation. Adrenaline, glucagon, GH, cortisol and thyroxine

32
Q

What inhibits fat metabolism?

A

Insulin

33
Q

What is the first stage in fat metabolism?

A

Adipose tissue TAG are hydrolysed by the enzyme hormone-sensitive lipase to release fatty acids and glycerol

34
Q

What is the first stage of fat metabolism called?

A

Lipolysis

35
Q

How are fatty acids carried to tissues?

A

This is done via the blood stream bound non-cavelently to albumin

36
Q

What are albumin bound fatty acids known as?

A

Non-esterified fatty acids (NEFA) or free fatty acids (FFA)

37
Q

What happens to glycerol in the liver?

A

It may be oxidised, converted to glucose or used in the synthesis of TAGs

38
Q

What is Beta-oxidation?

A

The process by which fatty acids are oxidised to release energy

39
Q

Where does beta-oxidation occur?

A

Mitochondria

40
Q

Why does beta-oxidation not occur in cells of the central nervous system?

A

Fatty acids do not readily cross the blood-brain barrier

41
Q

What needs to happen before fatty acids oxidised?

A

They have to be activated

42
Q

How are fatty acids activated?

A

Link the fatty acids to coenzyme

43
Q

What is required for the activation of fatty acid?

A

ATP and is catalysed by fatty acyl coA synthase

44
Q

Where does the activation of fatty acids occur?

A

Outside of the mitochondrion

45
Q

How does the activated fatty acid cross the inner mitochondrial membrane?

A

Carnitine shuttle

46
Q

What inhibits the transport of activated fatty acids?

A

Malonyl coA - an intermediate in the synthesis of fatty acids

47
Q

What happens if someone suffers from a defective micotchondiral fatty acid transport system?

A

They suffer from poor exercise tolerance and have usually large amounts of TAGs in their muscle cells therefore get lipid droplets in muscle

48
Q

What happens overall in beta-oxidation of fatty acids?

A

Oxidised the fatty acid and removes a C2 unit. The shortening fatty acid is cycled through the reaction sequence repeatedly removing a C2 unit each turn until only 2 carbon atoms remain

49
Q

What does the reaction sequence for beta-oxidation require?

A

Mitochondrial NAD+ and FAD and can;t occur in the absence of oxygen.

50
Q

Is ATP synthesised in b-oxidation

A

No direct synthesis

51
Q

What is special about all the intermediates in the pathway?

A

They are linked to coA and the C atoms of the fatty acid are converted to acetyl coA

52
Q

Which process derives more energy - FA oxidation or glucose oxidation?

A

Fatty acid oxidation

53
Q

What is the main convergence point for catabolic pathways?

A

Acetyl coA

54
Q

How many different ketone bodies are produced in the body?

A

3

55
Q

What are the different ketone bodies produced in the body?

A

Acetoacetate, acetone and b-hydroxybutyrate

56
Q

Where is acetoacetate synthesise?

A

Liver from acetyl coA

57
Q

Where is b-hydroxybutyrate synthesised and where from?

A

Liver from acely coA

58
Q

How is acetone synthesised?

A

Arises from spontaneous (non-enzymatic)

59
Q

When can the concentration of ketone bodies increase?

A

Increases in starvation and untreated type 1 diabetes

60
Q

Where are ketone bodies synthesised?

A

Liver mitochondria

61
Q

What enzymes are responsible for synthesis of ketone bodies in the liver?

A

Lyase and reductase enzymes

62
Q

What controls the lyase and reductase enzymes?

A

Controlled by the insulin/glucagon ration

63
Q

What happens when the insulin/glucagon ration falls?

A

Lyase is activated and reductive is inhibited and ketone body formation is activated

64
Q

What happens when the insulin/glucagon ratio increases?

A

The lyase is inhibited and the reductive is activated and cholesterol synthesis occurs

65
Q

What does the synthesis of ketone bodies require?

A

Fatty acids to be available for oxidation in the liver following excessive lipolysis in adipose tissue. The plasma insulin/glucagon ratio to be low, usually due to a fall in plasma insulin

66
Q

Ketone body function?

A

Important fuel molecules that can be used by all tissues containing mitochondria including the CNS

67
Q

What happens if acetoacetate and b-hydroxybutyrate are present in high concentrations?

A

They may cause acidosis (ketoacidosis)

68
Q

Why do you get the characteristic smell of acetone on someone’s breath if they have untreated type 1 diabetes?

A

Acetone is a volatile substance that may be excreted via the lungs

MEH A (19 decks)

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