Carbohydrates are composed of polymers of sugars. Where the carbonyl group is, determines whether the sugar is an aldose or ketose. The monomers of carbohydrates are Carbon, Hydrogen and Oxygen, these monomers are held together by covalent bonds. Since the polymer is made up of monomers, the structure of these determine the function of the polymer. The polymer must have the right bonds with the monomers so that the carbohydrate can do everything it needs to. Disaccharides are bonded together by a condensation reaction. This is because a disaccharide is composed of two monosaccharides. Carbohydrates can have a dehydration synthesis reaction, when this happens water is being lost. Glycosidic linkages are formed between two monosaccharides and is caused by the dehydration synthesis. Cellulose is a polysaccharide and can be found in the walls that enclose plant cells. Starch is also a polysaccharide of plants and is made up of only glucose monomers. In a cellulose molecule the OH molecules alternate down and up. In the starch molecule the OH molecules are facing down. Carbohydrates give our bodies energy, provide nutrients and help regulate metabolism.