Cellulose is a polymeric polysaccharide consisting of only one type of monosaccharide, i.e., glucose. Cellulose is a homopolymer. Starch is a variant of this but is present as a storehouse of energy in plant tissues. Starch forms helical secondary structures, and it can hold iodine molecules in the helical portion. The starch-iodine is blue. Cellulose does not contain complex helices and hence cannot hold iodine.