'What if oxygen is a poison?'
The first part of chocolotteyoghurt's ask is a typical request that I overlook. Cellular respiration is a fundamental process in biology, we can easily find an answer in any biology textbook or through the huge quantity of material available on web.
The last part, however, is more interesting because it’s often ignored that oxygen is a potential poison for us.
If our body is subjected to prolonged exposure to high partial pressures of oxygen — for example, in underwater diving and hyperbaric medicine— our lungs and our central nervous system may be damaged depending on the pressure and the time exposure, due the excessive concentration of oxygen in the blood.
Oxidant molecular oxygen.
During the cellular respiration process, oxygen produces intermediates known as ‘reactive oxygen species’ (ROS). These intermediates are free radicals —that is, molecules having an unpaired electron in the outer orbital— so they are highly unstable. To achieve a greater state of stability through the acquisition of an electron, they have a high level of reactivity with other molecules. In turn, the molecules that react with the free radicals become unstable and seek an electron, triggering a chain mechanism.
The formation of free radicals is a physiological process and a healthy body is properly equipped to fight them through an antioxidant system.
However, if the balance between pro-oxidants and antioxidants breaks, the cells can suffer serious damage such as DNA’s deterioration and structural modification of proteins.
To respond to fuzzy-cactus, the theory on the pathophysiology of aging derives from this oxidative stress, but nothing is demonstrated and, at the moment, miraculous cures anti aging are ineffective (eg, enzymatic antioxidants added to diet are destroyed during digestion, while vitamins antioxidants added to cells reduces the production of our “natural” antioxidants, leaving unchanged the level of free radicals).