Lipoprotein in general

Because lipids, such as cholesterol and triglycerides, are insoluble in water these lipids must be transported in association with proteins (lipoproteins) in the circulation. Large quantities of fatty acids from meals must be transported as triglycerides to avoid toxicity.

The plasma lipoproteins are complexes of lipid and protein which appear as spherical particles when viewed in the electron microscope with negative staining.

These lipoproteins have, in their basic structure, a lipid core to be transported (triacylglycerols (TAG), phospholipids, and cholesterol esters). A hydrophilic layer in which apolipoproteins are embedded thus provides structural stability as well as identity for each type of the lipoprotein.

Plasma lipoproteins are separated by hydrated density; electrophretic mobility; size; and their relative content of cholesterol, triglycerides, and protein into five major classes: from ultra-low-density lipoprotein (ULDL = chylomicrons) to very-low-density lipoprotein (VLDL), intermediate-density lipoproteins (IDL), and high-density lipoproteins (HDL).

Chylomicrons (CM) are the largest in diameter with the lowest density and the highest TAG content. The size of chylomicrons varies depending on the amount of fat ingested.

Lipoprotein lipase (LPL) is an extracellular enzyme that is essential in lipoprotein metabolism.
Lipoprotein in general