38. Considering the structural complexity of carbohydrates, it is not surprising that many of the cell surface molecules are glycoproteins and particular combinations of various glycoproteins can serve as identification of specific cell types. In these glycoproteins the carbohydrate moiety is added to the side chain of which amino acid? (A) Serine via an O-glycosidic bond (B) Tyrosine via an O-glycosidic bond (C) Lysine via an N-glycosidic bond (D) Histidine via an N-glycosidic bond (E) All the above are possible