Oxygen Everybody knows how important oxygen is to our lives. We can go on without any food for months and without any water for days. But no one can survive more than 5 minutes without oxygen (That is because the brain cells cannot tolerate the hypoxia condition or the condition which the oxygen level in the blood vessels is low, more than 5 minutes without paralyzing the brain cells. However, reports stated that there was a drowning person who had been in the water for more than an hour but his brain cells were not yet damaged. But who would be that lucky?)

But why is the oxygen that we breathe in every second poisonous? It can be so just like what an eastern saying, "everything has 2 sides; one is valuable, one noxious." This is the way nature keeps things in balance.

Scientists have discovered that the molecule of the oxygen is quite eccentric. That is there are 2 electrons in the 2 p orbital and that the moment also moves in the same direction, causing the oxygen to seem like it lacks 2 pairs of electron. That further gives the oxygen the possibility to react to all other biomolecules, resulting in free radicals, as in the following chemical equation;

A Free Radical is an atom or a molecule of any substances that have unpaired electrons, causing it to have rapid reactions and to be very poisonous. The only one remaining electron in the electron layer will not be stable. Therefore, it needs to seize the electrons from the molecules next to it. That consequently brings about chain reactions. If this occurs with the biomolecules or in the cells, the cells will function abnormally or will eventually be annihilated. This effect is a self-defense system created by the body in order to prevent germs and other unusual substances coming in the body through the oxygen. Nevertheless, if there are too many free radicals just like in our daily life where we consume contaminated food and are surrounded by pollution, the oxygen will be stimulated and changed into poisonous substances in order to get rid of atypical matters. If such substances are excessively produced, more tissues will gradually be destroyed which causes chain reactions. In consequence, the body will be aged and infected by numerous illnesses.