Amino Sugars in Biological Processes

Which monosaccharide serves as a building block for the synthesis of glycosaminoglycans (GAGs) in the extracellular matrix, playing a key role in joint health and cartilage formation?

Which monosaccharide is commonly found in O-linked glycoproteins, where it forms the initial sugar in the O-glycan chain, influencing protein stability and function?

Which monosaccharide is often found at the outermost end of glycan chains in glycoproteins and glycolipids, playing a critical role in cell surface recognition, immune responses, and protection against pathogens, as well as modulating cell adhesion and signaling processes?