Glycoprotein

A glycoprotein is a membrane-bound protein that has a carbohydrate attached to its extracellular surface. The carbohydrate is a oligosaccharide chain that is covalently bonded to the amino acid side chain of the protein. The chain can be of various lengths.  Glycoproteins and glycolipids make up a carbohydrate-rich region of the plasma membrane called the glycocalyx, and serve to protect the cell