Q. Define High Density Lipoproteins ?
High density lipoproteins (HDL) are the smallest of the lipoprotein species and transport approximately 20 to 30 per cent of plasma cholesterol. Nascent HDL in the form of bilayer discs containing apoproteins A and phospholipid is secreted by the liver and intestine. Cholesterol ester formed on HDL transfers to other lipoproteins via cholesterol ester transfer protein (CETP) in exchange for triglyceride. Mature HDL consists of two principal subclasses, HDL2 and HDL3.