 Now you know this is not going to be super easy, right? All right, so we're talking about intercalated cells. Let's just do this. We're talking about intercalated cells as opposed to principal cells in the collecting duct or the distal convoluted tubule. Okay, so that's where these guys are located. Now, I'm going to go with a lumen on, that's my left. And I'm going to do, there are two flavors of cells here. There are type A cells, and I'm just going to have you visualize blood because then I also have type B cells. And please understand that if I could put them on top of each other, if I had enough room to do that happily, I would. And then we'd have one lumen and one blood cell. I can't help it. I have to draw a bloodstream right here. Look, because that's where we're going to put it all into. And then I'm going to cut my, what is this? My, what's it called? Canvas in half. And here's my bloodstream on the other side. Okay, do you follow what I'm doing here? I hope so. And here's my lumen on the other side. So I'm doing two pictures side by side so you can compare and contrast. And type A cells on one side and type B cells are on the other. But remember, they're all found. They're scattered all around in the collecting duct and the distal convoluted tubule. And their whole goal is to react to, to changes in pH, sorry. And the cool thing is type A cells react to acidosis. And type B cells react to alkalosis. So if you are acedotic, type A cells are going to be the ones who do the job. The other thing that's really interesting, we get to keep track. Obviously, we're going to keep track of hydrogen ions. We're going to keep track of bicarb ions. I need to make them a different color. We're going to keep track of somebody that we haven't kept track of before, chloride ions. We don't see them very much. And we're going to keep track of potassium ions. These are the only guys that are coming to the mix. And we're going to keep track of them. This is the same in both scenarios. We type A's and type B's are actually identical except for where they place their transporters. We only have two flavors of transporters that we're going to look at. I can do this. We have one transporter that trades. It's going to have to be kind of a blue-ish one because this transporter trades bicarbonate ions and it's going to pull bicarbonate ions out HCO3. It's going to exchange them for chloride ions. Okay? Guess what? Exact same transporter. This is in the basolateral membrane of type A's which makes sense. We're too acidic. Let's reabsorb bicarbonate ions. It makes perfect sense, doesn't it? We're too basic. Let's get rid of bicarbonate ions. Exact same transporter just in, oops, it's purple, just on the other side of the cell. And it has, if we stick that same transporter on the luminal side, we're going to secrete bicarb. If we stick it on the basolateral side, we're going to absorb bicarb. It makes sense that we would want it where we would want it. Now, in order to make this happen, we also have a transporter who's left. Hydrogen ions and potassium ions. And so we have a transporter. My notes are over here. We're acidic. Let's go ahead and get rid of hydrogen ions. And you know what? Let's exchange it, the hydrogen ion, for a potassium ion. Okay, do you see what just happened? If you're acidic, you are going to reabsorb potassium. That's going to have an impact. That's going to affect potassium concentrations, which will have consequences. If we are alkalotic, we want to reabsorb the hydrogen ions. But look what's going to happen in exchange. We're going to secrete potassium. And in fact, there are potassium channels that are going to allow us to finish the job. So if your type A's are functioning, you're actually going to increase potassium concentrations in your blood. If your type B's are functioning, you're going to actually decrease potassium concentrations. However, you're going to increase hydrogen ion. You're going to decrease hydrogen ion. Now, it gets way more complicated because guess who is inside here? I don't know if it's more complicated, but guess who lives inside here? My buddy, my buddy, carbonic anhydrase, is in there doing all sorts of magic with hydrogen ions and bicarbonate ions and mixing and matching and switching and swapping and who goes where. And that's cool. We could follow that all along and we don't need to. The thing that I think is interesting and relevant is that we can use the exact same transporters and put them in different places and get two completely opposite outcomes. How are you? That's it, you guys. Kidneys are done. And if this is spring 2015, your exam is next. All right, may the force be with you.