So this is where our filtrate is actually found. So as the filtrate moves this way, we have the passive and active transport of different types of molecules and ions. So the first transport that we should discuss is found on this protein membrane. So this is an ATPase. It basically uses one ATP molecule and transforms that into an ATP. At the same time, it pumps three sodium ions basically against its electrochemical gradient and into the lumen of the proximal convolute tubule.