The Biochemistry of Redox Reactions

Abstract

Redox reactions are present in many physiological processes. Chemical and heat energy are provided by the oxidation of molecules by oxygen in many species. Although necessary to life, oxygen molecules can produce reactive molecules leading to diseases. Other reactive species including free radicals are also responsible for pathological states. The present chapter will only describe the basic redox reactions explaining the formation of reactive oxygen species (singlet oxygen, superoxide anion, hydrogen peroxide, alkoxyl radical, hydroperoxyl radical), of reactive nitrogen species (nitric oxide radical, nitrogen dioxide, peroxinitrite ion, nitrous acid) and of the very important lipid peroxides. The Fenton reaction plays an important role in the formation of reactive species and the mechanisms will be discussed. The organisms are equipped with defence mechanisms; both enzymatic (superoxide dismutase, catalase, peroxidase) and non-enzymatic reactions, some of them including the scavengers are summarized here.