Carbohydrates all consist of carbon, hydrogen and oxygen (CnH2nOn), yet not all forms of carbohydrate can be metabolised. The primary example of a carbohydrate that is used almost universally within living organisms is glucose, which is a monosaccharide. However, larger molecules (disaccharides, oligosaccharides and polysaccharides) are also metabolised within our bodies. Other examples include fructose and galactose.