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Free Radicals, Types, Sources and Damaging Reactions

Submitted by Dr. Tamer Fouad, M.D.

Types of Free Radicals in the body (continued)

Hydrogen peroxide:

Hydrogen peroxide is not a free radical but falls in the category of reactive oxygen species. It is an oxidising agent that is not particularly reactive but its main significance lies in that it is the main source of hydroxyl radicals in the presence of transition metal ions (Cheeseman and Slater, 1993). It is also involved in the production of HOCl by neutrophils.

Hydrogen peroxide can be generated from the two electron reduction of oxygen. In biological systems hydrogen peroxide is generated by the production of superoxide: two superoxide molecules can react together to form hydrogen peroxide and oxygen:

                             2O2?⁻+ 2H⁺? H2O2 + O2

    The above reaction is called a dismutation reaction as the radical   reactants produce nonradical products.

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