ABSTRACT
The meaning of such a paradox is clear for a biologist interested in oxidative stress: oxygen, although necessary for all forms of aerobic life, is one of the most highly toxic pollutants on the earth (Balentine, 1982). Beyond this “first order” paradox, a second one, less obvious to comprehend, is almost as important and concerns the heart of cellular metabolism. Most of the basic redox reactions involved in either oxygen production, during photosynthesis for example, or oxygen consumption, during mitochondrial respiration, require metalloproteins that contain copper or iron. Although essential, both these transition metals, as discussed below, are major pro-oxidants because of their ability to activate reduced forms of oxygen, which are natural side-products of the basic reactions mentioned above, and also by their interference with antioxidant mechanisms.
