Glycoproteins  

The name glycoprotein itself describes the molecule. It consists of protein and carbohydrate.

The monosaccharides which are available in the glycoproteins may be glucose, mannose, xylose , N-acetylgulcosamine, galactose, and others.

Addition of sugar to protein is called as glycosylation. Glycosylation may be N-glycosylation or O-glycosylation. The type of glycosylation depends on the addition of the sugar. In N-glycosylation, sugar is added to asparagine. In O-glycosylation, sugar is added to serine, hydroxylysine, hydroxyproline, or theonine.

Mucin is a glycoprotein available in the human body. Sugars are attched to mucins. So mucins are able to hold water . They are also proteolysis resistant to the digestive enzymes.

Antibodies are glycoproteins. These glycoproteins interact with the antigens.  Major Histocompatibility complex or MHC molecules are also glycoproteins. They act with T cells

Some other glycoproteins are zona pellucida components needed for sperm-egg interaction, structural glycoproteins which help in binding tissues. Glycoproteins in egg white and blood plasma.