Free radicals are chemicals containing an unpaired electron. They are of immense pathological importance due to their considerable reactivity; they may:
- attack and modify any cellular chemical:
- peroxidation of lipids to damage membranes
- cross-linking of proteins by the formation of disulphide bonds
- induce mutations in DNA
- catalyze the formation of more radicals
They are the final common pathway of a number of cellular insults. Aside from the natural tendency for free radicals to decay spontaneously, there are a number of physiological defence mechanisms to prevent free radical propagation.