Lipids III: Lipoprotein Complexes and Cholesterol Transport

Question 1

What is a Lipoprotein Complex? What are its constituents? What are the different Lipoprotein Complexes? What gives them their specificity?

Answer 1

a

Question 2

Overview of Lipoprotein Complexes

Answer 2

Question 3

This Lipoprotein Complex delivers dietary TGs from Intestine to peripheral tissues

Answer 3

Chylomicrons

Source: Small Intestine epithelial cells

“Core” Contents: dietary TGs (mainly), with small amounts of Cholesterol Esters and Cholesterol

Function: deliver dietary TGs and fat-soluble vitamins (A,D,E,K) from Small Intestine to peripheral tissues,

Apolipoproteins:

ApoB-48 - essential for assembly and secretion of Chylomicrons in Small Intestine epithelial cells

(source is Small Intestine)

ApoC-II - activates Lipoprotein Lipase, which hydrolizes TGs –> FFAs in peripheral capillaries

(added to Chylomicron from HDL when Chylomicron is in bloostream; once Chylomicron leaves capillaries, ApoC-II falls off Chylomicron and is returned to HDL)

ApoE - allows Chylomicron to bind to Liver after it has delivered its contents to capillaires

(added to Chylomicron from HDL; remains attached to Chylomicron so it can enter the Liver)

Question 4

This Lipoprotein is produced in secreted form liver

Answer 4

VLDL (Very Low-Density Lipoprotein)

Source: Liver (produced from remnant of Chylomicron that returned to Liver

“Core” Contents: TGs (added in Liver) and Cholesterol (added in Liver)

Function: deliver TGs to

Apolipoproteins

ApoB-100 - essential for synthesis and packaging of VLDL; is ALSO a ligand for LDL receptor

(source is Liver)

ApoC-II - activates Lipoprotein Lipase in tissues

(added to VLDL from HDL when VLDL is secreted from Liver; once VLDL has delivered TGs to peripheral tissue, ApoC-II is returned to HDL)

Apo-E

(added to VLDL from HDL; remains attached to VLDL so it can enter Liver)