5 Lipid transport

Question 1

How do we get cholesterol?

Answer 1

Some dietary
Mainly synthesised in the liver

Question 2

Lipids are hydrophobic, what does this mean?

Answer 2

• insoluble in water
• problem for transporting in blood
• transported in blood by carriers:
  -albumin - fatty acids
  -lipoprotein particles

Question 3

Lipoprotein definition

Answer 3

Sphere of phospholipids used to transport lipid in bloodstream

Question 4

Chylomicron function

Answer 4

Transports dietary TAGs from intestines to tissues

Question 5

VLDL function

Answer 5

Transports liver synthesised TAGs to adipose tissue for storage

Question 6

IDL function

Answer 6

Transports liver synthesised cholesterol from liver to tissues

Question 7

LDL function

Answer 7

Transport of liver synthesised cholesterol to tissues

Question 8

HDL function

Answer 8

Transports excess cholesterol from peripheral tissues to liver for disposal as bile salts

Question 9

Density of lipoproteins order

Answer 9

Least
Chylomicron
VLDL
IDL
LDL
HDL
Most

Question 10

Size of lipoprotein order

Answer 10

Biggest
Chylomicron
VLDL
IDL
LDL
HDL
Smallest

Question 11

When are Chylomicrons present in blood?

Answer 11

4-6 hours after eating

Question 12

What do chylomicrons look like after flotation ultracentrifugation?

Answer 12

Creamy appearance

Question 13

How is density of lipoproteins measured?

Answer 13

Flotation ultracentrifugation

Question 14

Apolipoprotein definition

Answer 14

Peripheral and integral proteins on lipoproteins
Peripheral - on top
Integral - pass through

Question 15

Apolipoprotein function

Answer 15

• structural: packaging water insoluble lipids
• functional: cofactor, ligands for cell surface receptor

Question 16

Lipoprotein lipase function

Answer 16

Hydrolyses TAGs in lipoprotein
Needs ApoC-II as cofactor

Question 17

What is the cofactor of lipoprotein lipase?

Answer 17

ApoC-II

Question 18

When does a Chylomicron become a Chylomicron remnant?

Answer 18

When lipid content drops below 20%

Question 19

Relationship between VLDL,IDL and LDL

Answer 19

VLDL > IDL > LDL
IDL - 30% depletion
LDL - 10% depletion

Question 20

What is bad cholesterol?
Why?

Answer 20

LDL
- Longer half life: more susceptible to oxidative damage
- no apoC/E: no efficiently cleared by liver

Question 21

What happens to oxidised LDLs?

Answer 21

Taken up by macrophages
Foam cells form
Can cause atherosclerosis

Question 22

How do LDLs enter tissues?

Answer 22

Receptor mediated endocytosis

Question 23

What happens in receptor mediated endocytosis?

Answer 23

Receptors for ApoB-100 ligand on LDL allow LDL to be endocytosed
LDL digested by lysosomes

Question 24

What is good cholesterol?
Why?

Answer 24

HDL
- Removes excess cholesterol from peripheral tissues
- Takes to liver or steroidogenic cells to be removed
- Reduced chance of foam cells and forming atherosclerotic plaques

Question 25

Hyperlipoproteinaemia defintion

Answer 25

High levels of 1 or more classes or lipoprotein

Question 26

Causes of hyperlipoproteinanemia

Answer 26

Overproduction Under removal

Question 27

What is type I hyperlipoproteinaemia?

Answer 27

Chylomicron present in plasma even when fasting Due to defective LPL

Question 28

What is type IIa hyperlipoproteinaemia?

Answer 28

- High levels of oLDL > foam cells > risk of atherosclerosis - Due to defective LDL receptor so LDL gets oxidised *familial hypercholesteroaemia*

Question 29

What is type III hyperlipoproteinaemia?

Answer 29

Raised IDL and Chylomicron remnants Due to defective apoE

Question 30

What is the first treatment of hyperlipoproteinaemia?

Answer 30

- DIET : reduced saturated fats and lipids, increase fibre - LIFESTYLE : exercise, stop smoking - reduces cardiovascular risk

Question 31

Second treatment of hyperlipoproteinaemia

Answer 31

- **STATINS** : inhibits HMG-CoA reductase, used in cholesterol synthesis so less cholesterol made - **BILE SALT SEQUESTRANTS** - bind bile salts in GI tract so liver produces more bile acids (uses cholesterol)

Question 32

What is hypercholesteroaemia?

Answer 32

High levels of cholesterol in blood

Question 33

What is the normal cholesterol level in blood?

Answer 33

<5mmol/L

Question 34

Signs of hypercholesteroaemia

Answer 34

- **XANTHELASMA** : yellow patches on eyelids - **TENDON XANTHEMA** : nodules on tendons - **CORNEAL ARCUS** : white/blue circle around eye

Question 35

What is xanthelasma and what it is a sign of?

Answer 35

Yellow patches on eyelids Hypercholesteroaemia - high levels of cholesterol

Question 36

What is tendon xanthema and what is it a sign of?

Answer 36

Nodules on tendon Hypercholesteroaemia- high levels of cholesterol

Question 37

What is corneal arcus and what is it a sign of? Difference in young and older people

Answer 37

White/blue circle around eye Hypercholesteroaemia- high levels of cholesterol Normal in older people Concerning in younger people

Question 38

Process of plaque formation

Answer 38

1) LDL have longer half life so get oxidised 2) oLDL engulfed by macrophages 3) foam cells made + accumulate in intima of blood vessels 4) fatty streak formed 5) evolves into atherosclerotic plaque > angina 6) plaque ruptures 7) thrombosis (clotting) > stoke or myocardial infarction

Question 39

What can a ruptured plaque cause?

Answer 39

Stroke Myocardial infarction