Carbohydrates are made up of smaller units called monosaccharides. These are the simplest form of carbohydrates and cannot be broken down further into smaller sugar molecules. The most common monosaccharides include glucose, fructose, and galactose.
When two monosaccharides join together, they form a disaccharide. Examples of disaccharides include sucrose (glucose + fructose), lactose (glucose + galactose), and maltose (glucose + glucose).
When many monosaccharides or disaccharides link together, they form polysaccharides. These are complex carbohydrates and include substances like starch, glycogen, and cellulose. Polysaccharides serve various functions in living organisms, such as energy storage (starch and glycogen) and structural support (cellulose in plants).