noun, plural: glycolipids
A carbohydrate, usually an oligosaccharide, that is covalently linked to a lipid molecule, such as those found in the cell membrane
Glycoconjugates are carbohydrates that are covalently linked to another biomolecule via glycosylation and the carbohydrate constituent of the complex is called a glycan. Examples of glycoconjugates are glycoproteins, glycopeptides, peptidoglycans, glycosides, glycolipids, and lipopolysaccharides.
A glycolipid is a carbohydrate that is covalently linked to a lipid. Glycolipids are biomolecular structures in the phospholipid bilayer of the cell membrane whose carbohydrate component extends to the outside of the cell.
Glycolipids are essential in providing stability of the plasma membrane. Furthermore, they are also associated with cell to cell interactions, e.g. cell adhesion to form a tissue. They also facilitate cellular recognition, which is important in immunologic functions.
An example of a glycolipid is a glycosphingolipid. It is comprised of a carbohydrate and a sphingolipid linked together by a glycosidic bond. Hydrolysis of the glycosphingolipid, thus, yields sugar, fatty acid, and sphingosine (or dihydrospingosine). The glycosphingolipids are part of the cell membrane and are involved in cell-cell interactions.
Another example of glycolipid is a glyceroglycolipid. It is comprised of a glycerol backbone and at least one fatty acid. It includes the galactolipids and sulfolipids.
Human blood types (A, B, AB, O) are based on the glycolipids on the surface of erythrocytes. The oligosaccharide component of the glycolipid determines the blood group antigen. For example, blood type A has N-acetylgalactosamine, blood type B has a galactose. Blood type AB has both antigens whereas blood type O lacks these antigens.