And what this complex does is it goes on to activate two other proteins, as we'll see in just a moment. One of the proteins is known as C Three. And that's exactly why sometimes the C four B C two B complex is known as the C Three convertes. And the other protein that this can activate is the C Five, as we'll see in just a moment. So let's begin with the C Three. So here we have the inactive form of C Three that is moving around, circulating in the bloodstream.