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radical

Synonyms:
  • free radical
Chemistry. Molecule or part of a molecule bearing unpaired electrons. They may have strong chemical reactions which can damage cellular material, especially DNA (oxidative stress). Hydrogen peroxide is a well-known radical. Radicals which can be essential to enzymatic reactions occur in cells as the result of metabolic processes and from external physical or chemical influences. Radicals are rapidly eliminated within cells by molecular scavengers.