Polysaccharides are polymers made of many monosaccharide monomers joined by condensation reactions. Each condensation reaction removes a molecule of water and forms a glycosidic bond between two monosaccharides.Starch, glycogen and cellulose are polysaccharides of glucose. Starch and glycogen are made of α-glucose and act as energy stores in plants and animals respectively. Cellulose is made of β-glucose and is a structural polysaccharide in plant cell walls.Polysaccharides are very large molecules and are insoluble in water. This makes starch and glycogen good energy stores, because they do not affect the water potential of the cell and cannot diffuse out of it.Polysaccharides can be broken down by hydrolysis, which adds water to break the glycosidic bonds and eventually releases the monosaccharides. In the body these reactions are catalysed by enzymes, for example amylase hydrolyses starch into maltose.