Carbohydrates are one of the most widely occurring types of organic compounds. The carbohydrates include sugars, starches, and celluloses. They all contain carbon, hydrogen, and oxygen following a general formula of C_x(H₂O)_y, the ratio of hydrogen to oxygen is always 2:1. It must be stressed that while all carbohydrates fit this formula not all organic compounds which fit this formula are carbohydrates, for example ethanoic acid C ₂H₄O₂, is classified as an acid, not a carbohydrate. On combustion carbohydrates produce carbon dioxide, water, and energy. Plants manufacture simple carbohydrates from carbon dioxide and water by photosynthesis. It is estimated that some 2 x 10¹¹ ton of carbohydrate are manufactured by plants each year. The most abundant form of carbohydrate is glucose, a simple sugar with the chemical formula C₆H₁₂O₆.

The relationship between the carbon atoms and the groups of atoms attached to them controls...