So this is the matrix, this portion, and this is the intermembrane space, this space between the inner membrane and the outer membrane. So the outer membrane is somewhere right here. So, as we can see from the diagram, our electron transport chain is located on the inner mitochondrial membrane and it consists of these special types of proteins as we'll discuss in a future lecture. So we have protein complex one, protein complex two, protein complex three and four, as well as other proteins, as we'll see in a future lecture. And we have this final protein molecule known as ATP synthase. So ultimately, what happens is protein complex one is responsible for accepting those high energy electrons from NADH molecules produced in glycolysis and the citric acid cycle.