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Science for Medicine > Lipids > Flashcards

Lipids Flashcards

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1
Q

What is a lipid?

A

It is an ester of a long hydrocarbon FA that is insoluble in water and is found in all living cells and tissues

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2
Q

What are the functions of lipid?

A

Energy storage, signalling molecules, enzyme cofactors, structural component of cell membranes, synthesis of vitamins and hormones

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3
Q

What are FAs?

A

They are hydrocarbon chains with a carboxylic group at one end, they can be saturated or unsaturated and their nutritional value can vary

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4
Q

What are the 4 types of fats?

A

Essential, good, bad and really bad

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5
Q

What are essential fats?

A

Fats that must be obtained from the diet as we can not produce C=C structures beyond C9 e.g. Linoleic acid

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6
Q

What are good fats?

A

Polyunsaturated e.g. plant oils

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7
Q

What are bad fats?

A

Unsaturated e.g. steric acid

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8
Q

What are really bad fats?

A

Trans fats e.g. margarine

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9
Q

What do gluconeogenic substances not contain?

A

FAs

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10
Q

What does the FA nomenclature of 12:1 and 16:2(2,8) mean?

A

12: 1- 12xC’s and 1xC=C
16: 2(2,8)- 16xC’s and 2xC=C (at C2 and C8)

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11
Q

What are the 3 major classes of lipids?

A

FA, triacylglycercide (TAG) and phospholipid

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12
Q

What are TAGs?

A

Main dietary lipid consisting of esters of FAs and glycerol

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13
Q

What are the properties of TAG?

A

It is anhydrous, highly reduced, combine in to water droplets and are major components of adipose tissue

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14
Q

What are the functions of TAG?

A

Energy storage (best), insulators, and forms depot fat in adipose tissue

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15
Q

What do phospholipids consist of?

A

Glycerol, 2xFA and a phosphate group

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16
Q

What are the properties of phospholipids?

A

Anhydrous

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17
Q

What are the functions of phospholipid?

A

Basic structure of cell membranes

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18
Q

What diseases are lipids involved in?

A

Atherosclerosis and steatorrhea

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19
Q

What is atherosclerosis?

A

Increases blood pressure due to an imbalance in lipid metabolism

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20
Q

What is steatorrhea?

A

Lipid malabsorption which leads to excess fat in pool and causes stool to float due to excess fluid. It has an oily appearance and foul smell

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21
Q

What causes steatorrhea?

A

Problems in bile secretion, pancreatic function and intestinal cell uptake

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22
Q

Where does digestion take place?

A

In the mouth and small intestine (mainly)

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23
Q

What is involved in digestion?

A

All lipids (mainly TAG), pancreatic enzymes, bile salts which cause emulsification and peristalsis

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24
Q

How are TAGs digested?

A

By pancreatic lipase which forms monoacylglycerol and 2xFAs

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25
Q

How are cholesterol esters digested?

A

Broken down to cholesterol and 1xFA

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26
Q

How are phospholipids digested?

A

Hydrolysed to lysphophospholiid and 1xFA

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27
Q

When are FAs releases from fat stores?

A

When energy supply is low

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28
Q

How are lipids absorbed?

A

The products of digestion form mixed micelles with bile salts and their contents are released when a brush border membrane is crossed

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29
Q

Do all FAs need micelles?

A

No, only long chain FAs

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30
Q

What are bile salts?

A

Derivatives of cholesterol that are biological detergents that form emulsions with mixed micelles and prevent lipids from combining in an aqueous environment

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31
Q

What is the brush border membrane?

A

Enterocytes that release the products of lipid into cells via diffusion

32
Q

How are lipids transported?

A

Chylomicrons, lipoprotein and albumin

33
Q

What is the function of chylomicrons?

A

They store TAG, FAs and cholesterol esters which are then releases by exocytosis into the blood via the lymphatic system

34
Q

What happens to TAG after it has been transported?

A

It is hydrolysed to FAs and glycerol by lipoprotein lipase when it reaches tissues

35
Q

What happens to FAs after they are transported?

A

They are used a energy or er-esterfired into TAG for storage

36
Q

What is the most dense out of chylomicrons, HDL and LDL?

A

Most- HDL

Least- Chylomicrons

37
Q

What are lipoproteins?

A

They have hydrophilic surfaces and hydrophobic cores and are transport free FAs

38
Q

Why are lipoproteins in a complex with serum albumin?

A

As serum albumin is the most abundant plasma protein with many binding sites

39
Q

How is cholesterol transported?

A

LDL- liver -> tissue

HDL- tissue -> liver

40
Q

What is VLDL?

A

Very low density lipoprotein

41
Q

What is albumin?

A

A protein which is used to transport unesterified carboxylic acids by binding to them

42
Q

How is excess carbohydrate and C from protein stored?

A

As FA residues and TAG in adipose tissue due to metabolism through acetyl CoA

43
Q

Where are FAs synthesised?

A

Liver, lactating memory gland, adipose tissue and kidney

44
Q

How are FAs synthesised from TAG?

A

They are released by hormone sensitive lipase (HSL) which is activated by adrenaline and inhibited by high plasma glucose and insulin

45
Q

Where does FA synthesis take place?

A

In the cytosol from acetyl CoA which uses ATP and NADPH

46
Q

What is acetyl CoA?

A

It is transported to cytosol by citrate shuttles. It is formed in mitochondria

47
Q

Why are citrate shuttles used to transport acetyl CoA?

A

It can’t cross the mitochondrial membrane, only the acetyl bit can

48
Q

When do citrate shuttles occur?

A

When mitochondrial [citrate] is high

49
Q

What are the products of FA synthesis?

A

Palmitic acid- C16

50
Q

What is elongation and desaturation?

A

The further modification of palmitate (ester of palmitic acid) in the mitochondria by digestive enzymes

51
Q

What is the function of Acetyl carrier protein (ACP)?

A

It links intermediates

52
Q

What is the catalyst involved in FA synthesis?

A

A multi enzyme complex

53
Q

What is the fate of FAs?

A

Acetyl CoA -> FA (in liver) -> TAG -> VLDL -> adipose tissue

54
Q

What is an example of an essential FA?

A

Omega 3, which is derived from linoleic acid and lowers cholesterol

55
Q

What are the effects of deficiencies in essential amino acids?

A

Growth retardation, reproductive failure and chronic intestinal disease

56
Q

What is B-oxidation?

A

The metabolism of FAs, by degrading 2xC at a time in the mitochondria matrix

57
Q

What are the products of B-oxidation?

A

1xacetyl CoA, 1xNADH, 1xFADH2

58
Q

What are the 3 stages involved in B-oxidation?

A

Activation, transport and degradation

59
Q

What is the process of activation in B-oxidation?

A

FAs are activated in the cytoplasm and forms acyl CoA

60
Q

What is acyl CoA?

A

A temporary compound formed when acetyl CoA binds to a long-chain FA

61
Q

What is involved in the transport phase of B-oxidation?

A

Carnitine shuttles

62
Q

What is the process of transport in B-oxidation?

A

Long chain FAs are transported from cytoplasm -> inside the mitochondrion, catalysed by carnitine fatty-acyl transferase

63
Q

What type of amino acid is carnitine?

A

Non-essential

64
Q

What is the function of molnyl CoA?

A

It inhibits carnitine fatty-acyl transferase in FA synthesis

65
Q

Can FA synthesis and degradation occur at the same time?

A

Nope

66
Q

What is the process of degradation in B-oxidation?

A

FA acyl CoA is dehydrogenated to form FADH2 and another intermediate, which is then hydrated and dehydrated to form NADH. Thylosis then occurs

67
Q

What is thylosis?

A

Forms acetyl CoA form dehydrogenated NADH

68
Q

What are steroid hormones?

A

They are chemical substances that serve as chemical messengers. Steroids are major lipid class

69
Q

What is the function of cholesterol?

A

It is the main starting material for steroid hormone synthesis, and is a component of cell membranes

70
Q

Where does cholesterol synthesis occur?

A

Liver

71
Q

What is the structure of cholesterol?

A

27xC and 4x benzene rings

72
Q

What are ketone bodies?

A

Water soluble compounds produced from excess acetyl CoA that are transported through the blood to peripheral tissues

73
Q

What are the functions of ketone bodies?

A

They can be re-converted into acetyl CoA or enter the CAC

74
Q

What is ketosis?

A

Metabolic process that burns stored fats when there is not enough glucose, due to starvation as TAGs aren’t being mobilised. The [ketone body] increases

75
Q

What is ketogenesis?

A

The production of ketone bodies which occurs in the liver and also produces acetone

76
Q

Why must acetone be expelled by respiration?

A

It is too unstable

77
Q

What are the 2 main types of ketone bodies?

A

Actetoacetate and 3-hydroxylbutarate

Science for Medicine (19 decks)

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