Glutathione. Computer-generated molecular model of the antioxidant chemical glutathione (C10.H17.N3.O6.S), a peptide thiol. This molecule prevents damage to important cellular components caused by reactive oxygen-containing chemicals such as free radicals. Free radicals are reactive atoms and molecules which occur naturally in metabolic processes, but may cause damage when present in excess. Atoms are colour-coded: carbon (white), hydrogen (small white), nitrogen (blue), oxygen (red) and sulphur (yellow).