Carbohydrates are a major source for living organisms. Our mitochondria break down carbohydrates and use the chemical energy released from its bonds to live. Carbohydrates have four functions, which include energy metabolism, structural components, and cell-to-cell contacts and recognition. The basic unit or monomer for carbohydrate is monosaccharide or simple sugars. An example of monosaccharide would be glucose, fructose, and galactose. Carbohydrates are composed of thousands of monomers are called polysaccharides. Some examples of polysaccharides would be starch, cellulose, and glycogen.