<unk>  is a generic term to designate any group of yellow-brownish fatty substances occurring in animal and plant tissues composed of phosphoric acid, choline, fatty acids, glycerol, glycolipids, triglycerides, and phospholipids (e.g., phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol).<unk>  was first isolated in 1846 by the French chemist and pharmacist Theodore Gobley. In 1850, he named the phosphatidylcholine<unk> e. Gobley originally isolated<unk>  from egg yolk—λέκιθος lekithos is "egg yolk" in Ancient Greek—and established the complete chemical formula of phosphatidylcholine in 1874; in between, he had demonstrated the presence of<unk>  in a variety of biological matters, including venous blood, bile, human brain tissue, fish eggs, fish roe, and chicken and sheep brain.<unk>  can easily be extracted chemically (using hexane, ethanol, acetone, petroleum ether, benzene, etc.) or mechanically. It is usually available from sources such as soybeans, eggs, milk, marine sources, rapeseed, cottonseed, and sunflower. It has low solubility in water, but is an excellent emulsifier. In aqueous solution, its phospholipids can form either liposomes, bilayer sheets, micelles, or lamellar structures, depending on hydration and temperature. This results in a type of surfactant that usually is classified as amphipathic.<unk>  is sold as a food supplement and for medical uses. In cooking, it is sometimes used as an emulsifier and to prevent sticking, for example in nonstick cooking spray.
Lecithin
Muconic acid
Heparan sulfate
Dermatan sulfate
Pectin
Phospholipid
Glycosaminoglycan
Glycerophospholipid