An acetylgalactosamine is the N-acetyl derivative of galactosamine which is a repeat unit in glycosaminoglycans.

An acetylgalactosaminyl is the univalent radical derived from acetylgalactosamine.

Glycoproteins are the proteins covalently attached to carbohydrates such as glucose, galactose, lactose, fructose, sialic acid, N-acetylglucosamine, N-acetylgalactosamine, etc. Glycolipids are carbohydrate-attached lipids. Their role is to provide energy and also serve as markers for cellular recognition.The antigens which determine blood types belong to glycoproteins and glycolipids

There's five; glucose, fructose, galactose, xylose and ribose.

Type O red cells do not contain the terminal sugars on the RBC membranes that distinguish type A (N-acetylgalactosamine), type B (galactose) or type AB (both). Additionally, the plasma of a type O individual contains naturally occurring anti-A, anti-B and anti-AB antibodies (unique to type O individuals) that are directed against non-self RBC ABO antigens.