What are the functions of glycoproteins in the plasma membrane ?

Glycoproteins have a range of functions and are used in the recognition of different cell types by cells. Cell signalling also involves glycoproteins whereby they act as receptors or binding sites for hormones or drugs. This may be used to trigger a secondary response within the cell. Additionally, glycoproteins are also used for cell adhesion. As well as stabilising the membrane by binding to water molecules.