Polysaccharide structure can be varied by differences in

monomers of MONOSACCHARIDES

Explanation:

Polysaccharides are large molecules formed from chains of POLYMERS linked together by glyosidic bonds. MONOMERS are small sub units that formed polymers, they are therefore the building block of a polysaccharides.  The monomers of polysaccharides are called monosaccharides (1 sugar molecule.) when two of these are joined together they formed disaccharides (two sugars.)

Polysaccharides are fromed by joining  together condensation, (loss of water molecules,)  of mutiple monosaccharides units and the reversal of this to add water molecules to sepate them to monosaccharies is  sugar Hydrolysis.

Example of polysaccharides are starch, glycogen cellulose

Example of monosaccharides are glucose, galactose.

Disaccharides are common table sugar, sucrose, maltose, lactose  

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.