Starch is the reserve substance in plant cells whereas cellulose is the most important structural component of the cell wall of plants. Both starch and cellulose are polymers of glucose. Starch is a branched polymers of α-D glucose units which are linked by α-1, 4 glycosidic bonds (but at branching, by α-1, 6 glycosidic bonds). Cellulose is a linear polymer of β-D- glucose units connected through β-1, 4 glycosidic bonds. In contrast to starch and glycogen, cellulose is insoluble in ordinary solvents and is not hydrolysed by boiling dilute acids. It gives no colour with iodine.