And if somehow complex four releases either this molecule or this molecule they can cause damage to the components of our cells because of their reactivity. So they can react with things like nucleic acids, so DNA molecules or they can react with other proteins and enzymes and they can disrupt their functions and that can cause damage to our cells. So we see that in complex four, on the normal conditions, when a total of four electrons are transferred to diatomic oxygen we form two water molecules which are harmless to the cell. But if oxygen only gains one or two electrons this can lead to the production of molecules such as superoxide ions or peroxide ions. And if these are released by complex four, that can cause damage to our cells. And because of that, we call these reactive oxygen species.