John Neustadt

The cellular environment is sensitive to the presence of free radicals, which are molecules with unpaired electrons. The most common types of free radicals are formed from the elements oxygen, nitrogen, carbon, sulfur, and chlorine. Cells continually need to balance redox potential (the tendency to gain or lose electrons). This potential can be skewed toward oxidation (a tendency to lose electrons), called oxidative stress, or reduction (a tendency to gain electrons), called reductive stress.