Lipoproteins

       Lipids are insoluble in water. However they must be transported from the tissue of origin to tissues in which they will be stored or consumed. They are carried in blood plasma from one tissue to another as plasma lipoproteins, macromolecular complexes of lipids and a specific carrier protein called apolipoprotein or apoprotein.

Structure of Lipoprotein:

       Lipoprotein have a central hydrophobic core of triacylglycerols (TAG) and cholesterol esters. The outer layer contains the more polar lipids (phospholipids, and free cholesterol) and the proteins (apoprotein). Lipoproteins are spherical except newly secreted HDL from liver or intestine. Nascent HDL is discoidal and requires the action of lecithin acyl cholesterol transferase (LCAT) in plasma to expand their core of neutral lipid and become spherical.