lipid transport

Question 1

How are lipids transported in the blood

Answer 1

2 percent bound to albumin but limited capacity

98 percent bound to lipoproteins particles consisting of cholesterol, phospholipid, cholesterol esters, proteins and TAG

Question 2

What is the total plasma lipid concentration

Answer 2

4000-8500 mg/L

Question 3

how is cholesterol transported around the body

Answer 3

cholesterol ester

Question 4

where is cholesterol synthesised

Answer 4

liver

Question 5

describe the structure of the lipoprotein

Answer 5

peripheral (apoC apoE) and integral (apoA apoB) apolipoproteins, phospolipid monolayer with a small amount of cholesterol, inner cargo (cholesterol, cholesterol ester and fat soluble vitamins)

Question 6

name the 5 classes of lipoproteins

Answer 6

Chylomicrons
VLDL
IDL
LDL
HDL

each consists of variable content of apolipoprotein, triglyceride, cholesterol and cholesterol ester

Question 7

describe the relationship between density and diameter of a lipoprotein

Answer 7

particle diameter inversely proportional to density.

more dense means higher percentage of protein

Question 8

describe the classes of apolipoproteins

Answer 8

6 classes A-H
can be integral or peripheral
structural role ( packaging water insoluble lipid)
functional role (co-factor for enzymes, ligands for cell surface receptors)

Question 9

summarise chylomicron metabolism

Answer 9

1. chylomicrons packed into small intestine in high quantity, apoB-48 combined before chylomicron enter lymph
2. enters blodstream via thoraxic duct, now in the left subclavian vein
3. apoC and apoE then combine to the chylomicrons
4. apoE LDL receptor binds it to hepatocytes
5. apoC LDL receptor on adipocytes, fatty acids unloaded into adipocytes until 20% left, then unbinds to LDL enzyme, apoC dissociates and chylomicron reminant returned to liver taken up by receptor mediated endocytosis

Question 10

where can lipoprotein lipase be found

Answer 10

capillary walls of the muscles and the adipocytes

Question 11

describe VLDL metabolism

Answer 11

VLDL role to transport trigycerol TAG to other tissues

does the standard LDL binding triglyceride release etc

Question 12

talk to me about VLDL, IDL, LPL

Answer 12

VLDL dissociates more than 30 percent TAG left and returns to liver

if depletes to around 30 percent particle becomes a short lived IDL particle, which can detach and return or continue bound

if depleted to around 10 percent, IDL loses apoC and apoE and becomes an LDL particle

Question 13

LDL function

Answer 13

provide cholesterol from liver to peripheral tissues

peripheral cells express LDL receptor and take up LDL via process of receptor mediated endocytosis

LDL no apoC or apoE so not cleared by the liver as efficiently

Question 14

characteristics of LDL in the blood

Answer 14

half life much longer, hence LDL more susceptible to oxidative damage

oxidised LDL taken up by macrophages that can transform to foam cells and contribute to formation of atherosclerotic plaques.