Living beings are made of organic and inorganic substances. According to the complexity of their molecules how can each of those substances be classified?
Inorganic substances such as water, mineral salts, carbon dioxide and molecular oxygen, are small molecules made of some atoms. Organic substances, in general, like glucose, fatty acids and proteins, are much more compound molecules made of sequences of carbons bound in carbon chains. The capacity of carbon to form chains is one of the major chemical facts that allowed the emergence of life on the planet.