Oxygen radicals arise in the body in four main ways. 18.104.22.168 Reoxidation of reduced flavins
Oxygen radicals may be generated by normal oxidative metabolism, and especially reactions involving the reoxidation of reduced flavin coenzymes (sections 22.214.171.124 and 126.96.36.199). During the reoxidation of flavins a number of radicals are generated as transient intermediates. If the whole sequence of reactions continues then there is no problem. However, by their very nature, radicals are unpredictable, and there will always be some escape of radicals from the reaction sequence. Overall, some 3—5% of the 30 mol of oxygen consumed by an adult each day is converted to oxygen radicals rather than undergoing complete reduction to water in the mitochondrial electron transport chain (section 188.8.131.52). There is, thus, a total daily formation of some 1.5 mol of reactive oxygen species that are potentially able to cause damage to tissues.
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