What is the monomer (single unit) that makes up the polysaccharides?

monosaccharides

Explanation:

The monomers of polysaccharides are the monosaccharides, otherwise known as the simple sugars. The monosaccharides are linked together by bonds known as glycosidic bonds.

For example; starch, cellulose, and glycogen are polysaccharides whose monomer units are glucose - a monosaccharide. The glycosidic bonds in starch and glycogen are alpha while those in cellulose are beta glycosidic bonds. The latter is formed when the hydroxyl group on the first carbon of the sugar is above the glucose ring while the former is formed when the hydroxyl group is below the ring.