Monosaccharides are the simplest carbohydrates that cannot be broken down further into other forms of carbohydrates. The chemical composition of almost all monosaccharides is of the form Cx(H2O)y where the least value of x is 3. Examples of monosaccharides include glucose, fructose and galactose. Usual monosaccharides are water soluble and colorless compounds that form crystals.
Disaccharides are complex carbohydrates that are created when two molecules of monosaccharide combined in a reaction that eliminates a molecule of water. Sucrose and lactose are examples of disaccharides. Sucrose is formed by the monosaccharide glucose and fructose and lactose is formed by glucose and galactose. The chemical structure of monosaccharides is such that same two monosaccharides can combine in different ways to form several different forms of disaccharides.