So this is the inner mitochondrial membrane, this is the mitochondrial matrix and this is the intermembrane space that exists between the two membranes of the mitochondrion. So protein complex one is also known as NADH dehydrogenase or NADH oxidoreductase. And that's because this is the protein complex that actually accepts those high energy electrons from the NADH molecules which were produced in glycolysis as well as the citric acid cycle. Now, this complex is actually a very large complex. In fact, it consists of about 46 individual polypeptide chains. And if we examine the shape of protein complex one, we'll notice that it looks like the letter L. So the letter L, which basically looks like this, contains a horizontal component and a vertical component.