Hello students. We're going to be talking about active transport in this lecture. So, we've already covered passive transport. If you haven't looked at that yet, make sure you go back and look at the passive transport before you cover active transport because that will be important. Right now, we're going to go over active transport. And there are different active transport processes, but they all have something in common. The one thing they have in common is that they require energy. And the second thing they have in common is that they're always moving things against their concentration gradient. So we're us we're going from we're moving things from low concentration to high concentration. So we're usually setting up a concentration gradient in some way. And so that's very important. And so we always require ATP if it's active transport. This might be indirect or direct but it requires ATP at some point. This will require the the use of protein pumps. So this is always occurring across the membrane because you have to have a membrane to separate the two areas to create the gradient and then you have to have pumps carrying this out. Okay. So these pumps can move one thing. They can move multiple things. They can move multiple things in the same direction or they can move multiple things in opposite directions. Um so we'll take we'll look at some examples of this. One main example that we're going to talk about pretty much every day and Sunday in this class is going to be the sodium potassium pump. You've heard probably heard of the sodium potassium pump. This is very important. You have to know what the sodium potassium pump does. It's very important. You're going to have to describe this in electrophysiology and resting membrane potential. It's important in understanding the the concentration gradients that we have within the cell. So where we have high concentrations of sodium and where we have high concentrations of potassium. It's important in this week when we're talking about the digestion and absorption and the movement of molecules and how they're going to get where they're going to go. So the sodium potassium pump creates these gradients that's going to allow for our absorption. Okay. So um this is going to be very important. So sodium potassium pump is a form of primary active transport meaning we're using ATP directly. Okay. And sodium potassium are being pumped against their gradients and they're being pumped in opposite directions. So it's an antiport pump. So it's opposite directions. Sodium is being pumped out. Three sodium ions go out and two potassium ions get pumped in. And this this uses up an ATP every time. Okay? So we use ATP. So, it's an enzyme with a pump with a channel or a carrier more more more correctly. Okay, so it's an enzyme with a carrier and it's going to move three sodiums out and two potassiums in and use up ATP at the same time. Okay, so how does this work? Sodium um this is outside. Okay, this is inside. sodium gets moved out, ATP gets broken down and potassium gets moved in. And this creates a high sodium gradient outside and a high um potassium gradient inside. Note this also puts more positive ions outside just along the membrane. Overall, we're all equal because of all other ions and everything else going on. But along the membrane, it's slightly more positive outside and slightly relatively more negative inside. And this creates our negative resting membrane potential. Okay, this let me say that again. This creates our negative resting membrane potential. potassium leak channels will will um in in what's the word for it increase that negative membrane potential or make it more negative but they do not set it up. The sodium potassium pump is what sets that up. So when we get to electrophysiology we need to know this. This creates a sodium gradient high sodium oxide. It creates a potassium gradient, high potassium inside, and it creates an electrical gradient, negative inside, positive outside along the membrane. Okay? Super important. You must know this. And this sets up your negative resting membrane potential. Okay? And this is a this is primary active transport because we're using ATP directly right then and there setting up this gradient. Okay. Secondary active transport little bit more complicated but not too much. Secondary active transport uses ATP indirectly. So we used a pump previously to establish a gradient. So let's say we use the sodium potassium pump and we establish a sodium gradient. Right? So we pump a bunch of sodium outside, we pump potassium inside. So now we have high potassium inside, we have high sodium outside. That means we have low sodium in the cell. Yes. Okay. So if there's low sodium in the cell and I open a sodium I open I put a channel in the membrane for sodium where does sodium want to go naturally? It's high outside, it's low inside. Where does it want to go? It wants to go inside. So if it goes inside, it's going to go down its gradient. Yes. So I created that sodium gradient with the sodium potassium pump. And now sodium wants to move down its gradient. So let's say that sodium channel that I put in also moves something else against its gradient. Maybe that something else is glucose. So we're talking about digestion this week. This is how we absorb glucose or amino acids or galactose. So and glucose and glactose can actually use the same transporter. So if glucco if sodium moves in it actually that transporter can bind to glucose as well and move glucose against its gradient. So glucose is going in against its gradient. There's high glucose in the cell and it goes against its gradient. That's secondary active transport. Sodium moves down its gradient established previously by the sodium potassium pump. Okay. And it carries glucose against its gradient. That's secondary active transport. Okay. So, one is moving down its gradient pre previously established by a pump. The second one is moving against its gradient. That's the secondary active transport. Okay, there we go. So, another type of a of of ATP or active transport is vicular transport. Meaning, we're using we're creating vesicles to move things. This is big stuff. like we're just like taking our membrane and surrounding something and pulling it in. And that might be um solutes and everything in there like the fluid outside the cell and the solutes there and kind of gripping it and and pulling it in in a vesicle. Um we might also have a vesicle of stuff that we've made. So, we're secretreting something and we're going to like have that vesicle merge with our membrane and release the contents and also remember this is a way that we change the membrane because we're actually adding to that membrane when we do that. So, we expose those contents. So, we exocytose or we endoccytose. We take it in or exocytose. This is vicular transport and we can do that all the way you know on both sides of the cell. This requires energy to do that because you've got it takes a lot of energy to take your membrane and engulf something or release it. And so this is another type of vicular transport uh active transport. So endoccytosis is cell eating big stuff like if I'm eating cells or or or large particles this is fagocytosis. If I'm doing more solutes um fluidl like stuff it's pinoytosis. how I remember the difference between the two. Um, pino is like wine, right? There's a it's a type of wine. So, pino is drinking cell drinking. So, that helps me remember make the connection that that is the drinking the fluid one. And fo um is like mouth or eating. And so, that's the big chunky stuff. And receptor mediated endoccytosis is where like specific things bind to receptors that are on the membrane and that initiates that process. So in the presence of those solutes, they bind and then we can now take that in. Okay? And that's really important for like cholesterol and hormones and iron and certain things to get taken into the cell. And so this allows um for things to come in and they'll be taken in in a vesicle or and then we'll talk about the exocytosis piece. An exocytosis is the expulsion of these contents. So the me so you've got a vesicle and that fuses with the membrane and exposes those contents. And you could take stuff in on one side and have it transport across the cell and then expose it on the other side. This is transcytosis. So we're transporting across the cell and doing both processes. So this is an example of exocytosis. You've you've probably remember exocytosis when we talked about the neuromuscular junction and the release of acetylcholine at the neuromuscular junction in um muscle cell contraction. So that was exocytosis. Okay. And so here's an example of the secrettory vessels, the pancre pancreatic acner cells. Remember they release digestive enzymes and we're talking about that in in class this week. And they release digestive enzymes that are then go into the duct and then travel down to the intest small intestine and will be there ready to digest to be activated and break down the intestinal contents. So, our next topic is going to be the cell cycle and cell division. Please contact me if you have any questions on what we've covered so far. I hope to see you there.