They play huge role in organisms, every living organism needs proteins. - enzymatic role ( they build enzymes which lower an activation energy in reactions and increase reaction speed) - hormonal role (they build hormons) - structural role (for example keratin) - transport role ( for example hemoglobin) - energetic role ( for example aleurone grains in plant cells or they are used to gain energy in human organism when it's out of lipids and carbohydrates)