Carbohydrates are of special importance because they are direct products of photosynthesis and are therefore the primary energy storage compounds and the basic organic substances from which most other organic compounds found in plants are synthesized.

In organic chemistry, a carbohydrate is a biomolecule consisting of carbon ©, hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula Cm(H2O)n (where m may or may not be different from n).