ABSTRACT
When they hear the term respiration, most people immediately think of breathing. Furthermore, most people know that we breathe to get enough oxygen, which of course is absolutely necessary for us to survive. Far fewer, however, know exactly why we need oxygen. We have already alluded to the answer. Many living things, including animals and many microorganisms, use oxygen to oxidize biological molecules in order to obtain the energy these biological molecules contain. Not all organisms, however, use oxygen for this purpose. As we will see, many microorganisms use other molecules precisely the way we use oxygen-to oxidize biological molecules. No matter which molecules are used, the slow incremental breakdown of biological molecules necessary for ATP production is called cell respiration. Essentially, breathing is simply the way animals get the oxygen needed to produce ATP. And without ATP, life is impossible.
