ABSTRACT
A free radical is an atom or molecule with at least one unpaired electron. This property makes free radicals highly reactive towards other molecular species. They are produced:
as a normal product of oxidative phosphorylation
by enzymatic systems (e.g. during the enzymatic synthesis of prostaglandins, NADPH [nicotinamide adenine dinucleotide phosphate] oxidase system of phagocytes)
by non-enzymatic oxidation catalysed by iron or catalytic metals such as copper
by ionising radiation
by photo-oxidation (e.g. ultraviolet [UV] light)
by auto-oxidation of lipids.
