A class of lipoproteins of small size (18-25 nm) and light (1.019-1.063 g/ml) particles with a core composed mainly of cholesterol esters and smaller amounts of triglycerides. The surface monolayer consists mostly of phospholipids, a single copy of apolipoprotein b-100, and free cholesterol molecules. The main LDL function is to transport cholesterol and cholesterol esters to extrahepatic tissues.