lipoprotein

thumb|250px|Structure of a chylomicron (the largest lipoprotein). ApoA, ApoB, ApoC, ApoE are [[apolipoproteins; green particles are phospholipids; T is triglyceride; C is cholesterol ester.]]

A lipoprotein is a biochemical assembly whose primary function is to transport hydrophobic lipid (also known as fat) molecules in water, as in blood plasma or other extracellular fluids. They consist of a triglyceride and cholesterol center, surrounded by a phospholipid outer shell, with the hydrophilic portions oriented outward toward the surrounding water and lipophilic portions oriented inward toward the lipid center. A special kind of protein, called apolipoprotein, is embedded in the outer shell, both stabilising the complex and giving it a functional identity that determines its role.