A polysaccharide consisting of various proportions of two glucose polymers, amylose and amylopectin. It occurs widely in plants, especially in roots, tubers, seeds, and fruits, as a carbohydrate storage product and energy source. Starch is therefore a major energy source for animals. When digested it ultimately yields glucose. Starch granules are insoluble in cold water but disrupt if heated to form a gelatinous solution. This gives an intense blue colour with iodine solutions and starch is used as an indicator in certain titrations.