glycolipid

glycolipid, any of a group of molecules consisting of a carbohydrate (sugar) moiety attached to a lipid (fat) backbone. Glycolipids are important components of cell membranes and are particularly abundant in tissues of the nervous system.

Glycolipids are classified based on the structure and complexity of their lipid and carbohydrate components. The two main classes of glycolipids are glycosphingolipids and glycoglycerolipids, each of which are divided into subtypes depending on their chemical composition and biological roles. Glycosphingolipids are the most common glycolipids in animal cells. They are built on a ceramide backbone, in which a sphingosine molecule is linked to a fatty acid. Glyceroglycolipids have a glycerol backbone and at least one fatty acid and a carbohydrate. They are found mainly in plants, algae, and some bacteria.

Glycolipids are amphipathic, wherein the carbohydrate component is hydrophilic (attracted to water) and the lipid tail is hydrophobic (repels water). Thus, glycolipids orient themselves within the lipid bilayer of cell membranes such that the carbohydrate portion of the glycolipid molecule is exposed on the cell surface. This enables the molecule to interact with other molecules in the extracellular environment. In particular, glycolipids appear to have a role in the process of cell-cell recognition and cell adhesion, whereby a carbohydrate-binding protein on one cell binds to a complementary carbohydrate group on a glycolipid or glycoprotein on an adjacent cell.