So this is the matrix side. This is the intermembrane of the mitochondria. We have complex three, and this is the intermembrane space. And this protein carrier molecule, Cytochrome C, when it actually attaches a single electron, when the oxidized version is reduced, the Cytochrome C will actually detach itself. And because it's diffusible in water, it basically travels through the fluid and eventually attaches onto complex four found on the intramembrane side of complex four, as we'll see in the next lecture. So let's begin by summarizing what takes place in the first mini cycle, the first half cycle of the Q cycle.