text: Peroxides play important roles in biology.  Hundreds of peroxides and hydroperoxides are known, being derived from fatty acids, steroids, and terpenes. The prostaglandins are biosynthesized by initial formation of a bicyclic peroxide ("endoperoxide") derived from arachidonic acid.
  Many aspects of biodegradation or aging are attributed to the formation and decay of peroxides formed from oxygen in air.  Countering these effects, an array of biological and artificial antioxidants destroy peroxides.
  In fireflies, oxidation of luciferins, which is catalyzed by luciferases, yields a peroxy compound 1,2-dioxetane. The dioxetane is unstable and decays spontaneously to carbon dioxide and excited ketones, which release excess energy by emitting light (bioluminescence).