Explain why the level of oxygen increases as the level of exercise increase. (3marks)
During physical exercises, organism’s requirement of oxygen extremely increases. Oxygen is needed to provide muscles with energy, produced by mitochondria. Actually, at the outset, the level of oxygen decreases and the level of CO2 increases. That causes the pH lowering (the amount of H+ increases) of the blood, in other words, acidification. Our respiratory center, which is localized in the brainstem, becomes activated by detecting of H+ increasing and we start breathing faster and more deeply. As the result, blood is enriched by oxygen and its level increases.