Abstract
Reactive molecules and free radicals are used to define the reactive oxygen species that include superoxide, hydrogen peroxide, hydroxyl radical, hydroxyl ion, and nitric oxide. Antioxidants are responsible to eradicate the ROS in the human body. Antioxidant systems of the cell lessen the perturbations whereas oxidative stress is the result of when reactive oxygen species production exceeds the limit and overcome the cellular antioxidants which disturb the cell signaling and gene regulation systems. Only antioxidants can prevent or delay the oxidation of cellular oxidizable substrates. Heavy metals (Pb, Hg, Cd, Cr, Cu, Zn, Mn, Ni, Ag, etc.) are dangerous to human health; they enter into human body via food, drinking water and air. These heavy metals’ toxicity causes serious health issues and causes diseases in human body. High concentration of lead leads towards the complications in the synthesis of hemoglobin, renal effects, gastric and CNS disturbances. Mercury leads to abortion, congenital malformation and development changes in young children. Selenium cause fatigue and irritability, alopecia and fingernail loss, damage the renal, hepatic system. Antimony causes nausea, vomiting and diarrhea and cancer. Two mechanisms are involved in the production of superoxide firstly when ATP is not being produced by mitochondria, simultaneously promotive forces become higher in concentration and decrease in coenzyme Q pool and secondly, the high ratio of NADH/NAD+ in mitochondrial matrix, skeletal muscle, heart and liver using different substrates and inhibitors to determine site for production of reactive oxygen species. NADPH oxidase and mitochondrial electron transport chain is responsible for the formation of cell reactive oxygen species in targeted pancreatic beta cell and other cells for insulin. Reactive oxygen species play many roles in homeostasis and on physiological levels, excess of it causes cellular stress and death. Due to accumulation of heavy metals many types of cancers occur like lung cancer, kidney cancer, brain cancer etc
