According to the BioTopics website, a disaccharide forms when two monosaccharides are joined. An example of this is two glucose molecules that are combined when using condensation reactions and water removal.
When disaccharides are dehydrated, they join more rings and form what are known as polysaccharides, according to Sue Eggling of Clackamas Community College. In D-glucose, polysaccharides that are formed include glycogen and starch. Polymers can be hydrolyzed, which then form monosaccharides and disaccharides. Through these types of reactions, glucose molecules are stored and used up when energy is needed. Plants convert glucose into a starch, while animals convert glucose into a glycogen.