Lipids - HDLS,LDLS,Classification (Aug/23/2005 )

Hi everybody, I am reading a book on Physiology. I have gathered that Lipids are digested and eventually transported through the lymphatic system before being drained off into the bloodstream. However, they travel in the bloodstream as lipoproteins. Hence, I would like to know where do the lipids combine with proteins and what is the process that determines whether lipids are transported as HDL (High density lipoproteins) or LDLs ?

I sincerely hope you could enlighten me in this regard.
Thanks

Okay, once a lipid crossed into the enterocyte, it is packaged as a chylomychron (ApoB 48, lots of triglyceride, some cholsterol ester in the center and a 'shell' of phopholipid. Into the lymph duct it goes and thence to venous system. Before it hits the liver, it dumps off a lot of triglyceride into cells. Once it hits the liver, it is repackaged as an LDL particle with ApoB 100, some triglyceride and a lot more cholsterol ester. It deposits triglyceride and cholesterol ester into the cells (lots of the cholsterol ester gets deposited in arterial wall cells, this is where we get heart disease).
HDL is secreted via ABCA1 with no cholesterol ester and triglyceride, but has Apo A1 and A2 as protein. It gets lipids and cholesterol ester from peripheral tissue via LCAT and takes them back to the liver where they are processed for storage or converstion to bile acids.