Answer:
C. glycoproteins
Explanation:
Glycoproteins are proteins containing glycans (oligosaccharide carbohydrates) attached to amino acid side chains. These oligosaccharides are attached to the amino acid chain by a posttranslational modification referred to as glycosylation, a modification generally found in extracellular regions. Glycosylation refers to the chemical reaction in which a glycosyl donor (i.e., the carbohydrate) is attached to a functional group in the protein. The glycosylation sites play distinct functional roles for both cell interactions and cell recognition. Moreover, glycosylation sites are also essential for substrate recognition by an enzyme. For example, secreted cytokines are glycosylated, which is required for their binding to receptors.
