The structure of starch is more complex than that of cellulose. It is insoluble in cold water, but grinding and soaking makes them form a colloidal solution. Partial hydrolysis of starch and glycogen produces the disaccharide maltose and a low molecular weight dextran. Starch is but not a linear polymer. Hydrolysis of starch yields of two fractions. About 20% of the hydrolyzed product is a water-soluble material called amylose. Amylose is a linear chain of several thousand glucose units joined by alpha C-1 to C-4 glycoside bonds. Amylose solutions are colloidal dispersions of hydrated micelles. The majority of the starch is of much higher molecular weight substance, consisting of nearly a million glucose units, and called amylopectin. Molecules of amylopectin is a branched network of glucose units in addition to the linear chain connected by C-1 to C-6 glycoside links, and are essentially water-insoluble.