title: Oxygen--friend and foe.
mesh_terms: D005075:Biological Evolution; D055598:Chemical Phenomena; D002621:Chemistry; D005609:Free Radicals; D006801:Humans; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism* / Q000502:physiology
chemical_list: D005609:Free Radicals; D010100:Oxygen