So these complexes, these enzymes which basically reduce things like oxygen molecules, actually hold on to these molecules very tightly and they only let go under certain conditions. So we see that complex four holds the oxygen and its derivatives very tightly. It only releases it upon the conversion of these molecules into safer molecules as in this case, into water. But for the few ros molecules that are released in the process or for instance, when we form the peroxide in complex four, if the complex four accidentally releases the peroxide, we do have certain methods that our cells use to actually help us remove these harmful molecules from our body. And these methods includes using these special protective enzymes to find, to locate these ros molecules and to basically convert the ros molecules into something that are safer. So let's discuss two very important types of protective enzymes used by our human cells and many other eukaryotic cells.