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MEH > Lipipd Transport > Flashcards

Lipipd Transport Flashcards

1
Q

Why must lipids be transported bound to carried in the blood?

A

They are hydrophobic/insoluble in water

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2
Q

How are the majority of lipids transported in the blood?

A

Via lipoprotein particles

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3
Q

What do lipoproteins usually consist of?

A

Phospholipid
Cholesterol
Cholesterol esters
Proteins
TAGs

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4
Q

What is normal plasma glucose levels?

A

5mmol/L

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5
Q

What is the normal amount of cholesterol in blood plasma?

A

Less than 5mmol/L

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6
Q

Describe the structure of phospholipids

A

2 non polar hydrophobic fatty acid tails
Polar hydrophilic phosphate head

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7
Q

What are the functions of cholesterol?

A

Regulates membrane fluidity
Precursor of corticosteroids (steroid hormones)
Precursor of bile acids

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8
Q

What form is cholesterol transported in around the body?

A

As cholesterol ester

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9
Q

What enzyme catalyses the formation of cholesterol esters?

A

LCAT

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10
Q

Describe the structure of a lipoprotein

A

Phospholipid monolayer with small amount of cholesterol
Peripheral Apolipoproteins on outside of phospholipid monolayer
Integral apolipoproteins embedded in phospholipid monolayer
Cargo inside lipoprotein = TAG, cholesterol ester, fat soluble vitamins

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11
Q

Give 2 examples of integral apolipoproteins

A

ApoA
ApoB

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12
Q

Give 2 examples of Peripheral Apolipoproteins

A

ApoC
ApoE

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13
Q

How are lipoproteins classified?

A

By density

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14
Q

What are the 5 classes of Lipoproteins?

A

Chylomicrons
VLDL
IDL
LDL
HDL

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15
Q

What is the function of Chylomicrons and VLDLs?

A

Transport TAG

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16
Q

Where do Chylomicrons transport Triacylglycerols from and to?

A

Dietary TAG from the small intestine to adipose tissue

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17
Q

Where do VLDLs transport Triacylglycerols from and to?

A

TAGs synthesised in the liver to adipose tissue

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18
Q

What is the function of IDLs, LDLs and HDLs?

A

Transporting cholesterol

19
Q

Where does IDLs and LDLs transport chosterol from and to?

A

Cholesterol synthesised in the liver to tissues requiring cholesterol

20
Q

What is IDL in relation to LDL?

A

A short lived precursor of LDL

21
Q

Where do HDLs transport cholesterol from and to?

A

From cholesterol laden tissues back to the liver to be metabolised to bile salts for excretion

22
Q

What are Apolipoproteins?

A

They are the particular complement of associated proteins to a lipoprotein particle

23
Q

What are the 2 roles of apoproteins?

A

Structural - packaging water insoluble lipids
Functional - act as ligands for cell surface receptors, Co factors for enzymes

24
Q

What Apolipoprotein is added to Chylomicrons containing TAGs before they enter the lymphatic system?

A

ApoB(-48)

25
Q

Once Chylomicrons containing TAGs enter the blood, what 2 apoproteins are added?

A

ApoC
ApoE

26
Q

What is lipoprotein lipase?

A

Enzyme which breaks down TAG in lipoprotein particle to release fatty acids

27
Q

Which Apolipoprotein on Chylomicrons binds to Lipoprotein Lipase on adipocytes and muscle ?

A

ApoC

28
Q

Wha happens to ApoC when the TAG content of a Chylomicron has been reduced to about 20%?

A

ApoC dissociates
Leaves Chylomicron remnant

29
Q

What happens to Chylomicron remnants?

A

Return to liver
ApoE binds to LDL receptor
Chlyomicron remnant taken up by receptor mediated endocytosis

30
Q

What Apolipoproteins are added to VLDL when in the blood?

A

ApoB
ApoC
ApoE

31
Q

What happens to VLDL when it reaches the endothelial cells in muscle and adipose?

A

Binds to lipoprotein lipase
Fatty acids released and are taken up by muscle for energy production, in adipose fatty acids re synthesised into TAG for storage

32
Q

How do cells that need cholesterol obtain cholesterol?

A

Express LDL receptor and when LDL binds it takes it up via receptor mediated endocytosis

33
Q

Why are LDLs not efficiently cleared by the liver? (Have the longest half life)

A

Do not have ApoC or ApoE
Liver LDL receptor has a high affinity for ApoE

34
Q

What is the clinical relevance of high levels of LDL?

A

LDL susceptibility to oxidative damage due to its long half life
Oxidised LDL taken up by macrophages forming foam cells in intima of blood vessel
Foam cells form fatty streaks contributing to the formation of atherosclerotic plaques
Leads to atherosclerosis

35
Q

What are the 6 classes of Hyperlipoproteinaemias?

A

I
IIa
IIb
III
IV
V

36
Q

What are the clinical signs of Hypercholesterolaemia?

A

Xanthelasma
Tendon Xanthoma
Corneal Arcus

37
Q

What happens in hypercholesterolaemia?

A

Cholesterol gets deposited in various areas of the body

38
Q

What is Xanthelasma?

A

Yellow patches on eyelids

39
Q

What is Tendon Xanthoma?

A

Nodules on tendon

40
Q

What is corneal arcus?

A

Obvious white blueish circle around eye

41
Q

What happens when an atherosclerotic plaque grows and then ruptures?

A

Blood flow is reduced
Once ruptured thrombosis occurs causing clotting
Leads to stroke or myocardial infarction

42
Q

How are Hyperlipoproteinaemias initially treated?

A

Diet - reduce cholesterol and increase fibre
Lifestyle - more exercise, stop smoking

43
Q

What is the next step if the initial approach to treating Hyperlipoproteinaemia doesn’t work?

A

Statins - inhibit HMG-CoA REDUCTASE so inhibit cholesterol synthesis

Bile salts sequestants- more bile salts makes liver use up more cholesterol by producing more bile acids

MEH (33 decks)

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