Oxidation reactions
<p>Oxidation reactions can produce <a href="http://en.wikipedia.org/wiki/Radical_(chemistry)" title="Radical (chemistry)" >free radicals</a>. In turn, these radicals can start <a href="http://en.wikipedia.org/wiki/Chain_reaction" title="Chain reaction" >chain reactions</a>. </p>
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Although oxidation reactions are crucial for life, they can also be damaging; plants and animals maintain complex systems of multiple types of antioxidants, such as <a href="http://en.wikipedia.org/wiki/Glutathione" title="Glutathione" >glutathione</a>, <a href="http://en.wikipedia.org/wiki/Vitamin_C" title="Vitamin C" >vitamin C</a>, and <a href="http://en.wikipedia.org/wiki/Vitamin_E" title="Vitamin E" >vitamin E</a> as well as <a href="http://en.wikipedia.org/wiki/Enzyme" title="Enzyme" >enzymes</a> such as <a href="http://en.wikipedia.org/wiki/Catalase" title="Catalase" >catalase</a>,<a href="http://en.wikipedia.org/wiki/Superoxide_dismutase" title="Superoxide dismutase" >superoxide dismutase</a> and various <a href="http://en.wikipedia.org/wiki/Peroxidase" title="Peroxidase" >peroxidases</a>. </p>