So one and two, we form the peroxide molecule. In fact, when we discussed complex four, we said that a peroxide bridge is formed between the copper B atom and the heme A three group. Now, these two types of molecules are very, very reactive. 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.