Free Radicals in Tissue

Abstract

Evidence supports the idea that free radicals which are contained in detectable amounts in living tissue are essential intermediates in many metabolic pathways. Metabolic processes involve oxidoreduction, and oxidoreduction involves the flow of electrons. This flow may result in the formation of free radicals as intermediates in which two electrons may be transferred, one by one; the functioning of horse-radish peroxidase is a good example of this. On the other hand, a system may simply shuttle between two states differing by one electron as in the photooxidation of a chlorophyll complex in photosynthesis or the functioning of dihydro-orotic dehydrogenase. The study of free radicals is part of a larger problem, one involving shifts of charge whether or not radicals are formed.