As a result of accelerated metabolic rates
under stress conditions, elevated levels of free
radicals (in particular reactive oxygen species,
ROS) tend to be formed. ROS can have
beneficial roles, as in phagocytes where they
protect against bacteria and parasites. However,
if natural antioxidant mechanisms are not adequate
to quench excess oxygen radicals then they
can react with cell structures and attack proteins,
lipids, carbohydrates and nucleotides within
the cell, a state referred to as oxidative stress