And it also happens when this copper A gains an electron. Now, notice in the diagram we actually have two of these cytochrome C molecules in their reduced form. And that's because what happens is first a single cytochrome binds onto this section, giving off an electron. The electron ultimately ends up reducing this copper B. Then that oxidized, cytochrome C leaves and a second reduced cytochrome C binds and gives off an electron. So ultimately, we have two of these cytochrome C molecules, in their reduced form, being oxidized, give off two electrons.