Definition: Free radicals are destructive particles that form when oxygen reacts with certain molecules. Free radicals are defined as any atom or molecule that has a single unpaired electron in an outer shell.
Example: Because Free Radicals are so reactive they can cause unwanted reactions that result in cell damage and with a large amount can result in cell injury or death. Excessive amounts of free radicals may contribute to serious diseases such as cancer, myocardial infarction, diabetes, stroke, and other major disorders. Free radicals may contribute more to alcohol induced liver damage than alcohol itself. Free radicals from cigarette smoke has been implicated in triggering the process that promotes the development of emphysema.