lipoproteins

Question 1

how are most fatty acids taken up from the body?

Answer 1

from the diet

Question 2

why are TAGs packaged into lipoproteins?

Answer 2

not easily transported in the blood bc they’re hydrophobic

Question 3

what do lipoproteins consist of?

Answer 3

cholesterol and apoproteins

Question 4

what are chylomicrons?

Answer 4

dietary TAG lipoproteins

Question 5

how is liver derived TAG released?

Answer 5

as VLDL

Question 6

what are lipoproteins?

Answer 6

a method of transporting TAG, cholesterol and phospholipids and some vitamins between organs and tissues

Question 7

describe the structure of lipoproteins

Answer 7

hydrophobic core with cholesterol esters and TAG

outer layer of phospholipids, free cholesterol and apoproteins

Question 8

what do apoproteins do?

Answer 8

control fate of lipoproteins, interact with the cellular receptors and activate/inhibit enzymes

Question 9

where are apoproteins found in a lipoprotein?

Answer 9

embedded (e.g. apoB) or loosely bound (e.g. apoC)

Question 10

what is the main component and apoprotein of chylomicron?

Answer 10

TAG

B48

Question 11

what is the main component and apoprotein of VLDL?

Answer 11

TAG

B100

Question 12

what is the main component and apoprotein of IDL?

Answer 12

TAG, cholesterol

B100

Question 13

what is the main component and apoprotein of LDL?

Answer 13

cholesterol

B100

Question 14

what is the main component and apoprotein of of HDL?

Answer 14

protein

AI, AII, C, E

Question 15

what does apoB100 do?

Answer 15

controls metabolism of LDL

Question 16

what does apoB48 do?

Answer 16

controls chylomicrons

Question 17

what does apoE do?

Answer 17

controls receptor binding of particles –> makes the chylomicron a target for disposal

Question 18

what does apoC do?

Answer 18

enzyme inhibitor

Question 19

where is lipoprotein lipase found?

Answer 19

epithelium adjacent to target cells

Question 20

which apoprotein activates LPL?

Answer 20

apoC2

Question 21

what does LPL do?

Answer 21

degrades TAG in chylomicrons and VLDL – releases free fatty acids and glycerol for uptake by adjacent cells

Question 22

where are chylomicrons formed?

Answer 22

in the lumen of the gut

Question 23

what are chylomicrons made up of?

Answer 23

TAG, esterified cholesterol, phospholipids, B48

Question 24

describe the life of a chylomicron?

Answer 24

formed in gut lumen
released by exocytosis into lacteals into the bloodstream
in the blood it exchanges components with high density lipoproteins
HDL donates ApoC-II and ApoE to chylomicron.
ApoC-II activates LPL, which breaks down TAG and unloads FAs.
Gives ApoC-II back to HDL and becomes a remnant. Bc of ApoE - taken up by liver

Question 25

what is cholesterol a precursor to?

Answer 25

steroids and bile acids

Question 26

what regulates the uptake of cholesterol into cells?

Answer 26

HMG-CoA

Question 27

what does transcription factor SREBP do?

Answer 27

regulates expression of HMG-CoA reductase --> regulates how much cholesterol is taken in

Question 28

where is HDL assembled?

Answer 28

liver and intestine

Question 29

where does HDL transport cholesterol?

Answer 29

from peripheral tissues to the liver for disposal via bile

Question 30

how does HDL scavenge free cholesterol and what does it do with it?

Answer 30

via the ABCA1 transporter and esterifies it to cholesterol esters

Question 31

what effect do LDL and HDL have on the risk of heart disease?

Answer 31

LDL - increases CVD risk | HDL - cardioprotective

Question 32

what conditions are caused by high TAG levels?

Answer 32

atherosclerosis --> risk of CHD and stroke

Question 33

what condition is common In diabetes?

Answer 33

dyslipidaemia

Question 34

what do oxidised LDLs promote?

Answer 34

formation of atherosclerotic plaques

Question 35

what causes oxidised LDL formation?

Answer 35

smoking and diabetes

Question 36

how does oxidised LDL lead to plaque formation?

Answer 36

Scavenger receptors aren’t feedback regulated by cholesterol --> macrophages become lipid laden --> foam cells --> fatty streaks in arterial wall --> plaque formation

Question 37

how do statins work?

Answer 37

blocking HMG-CoA reductase inside the cells --> can't make cholesterol themselves so the cells have to meet cholesterol demand by taking cholesterol from the blood

Question 38

what is the mechanism of action of cholestryamine?

Answer 38

bind bile acids in the gut, preventing enterohepatic circulation

Question 39

what are the adverse effects of cholestryamine?

Answer 39

GI adverse effects mainly; nausea, flatulance, abdominal bloating, alteration of bowel habit

Question 40

what are the long term safety considerations of cholestryamine?

Answer 40

not systematically absorbed therefore the safety is good | fat soluble vitamins might be needed