In this video, we're going to talk about a classic example of primary active transport in the sodium-potassium pump. And so once again, the sodium-potassium pump is a classic example of primary active transport. As its name implies, the Sodium-Potassium Pump is going to pump or move sodium and potassium ions across the plasma membrane. But more specifically, the sodium-potassium pump is going to move the sodium and potassium ions in opposite directions across the plasma membrane, which means that the sodium-potassium pump is an antiporter, which recall from our previous lesson videos just means that some molecules will be pumped across the membrane towards the outside of the cell whereas other molecules are going to be pumped across the membrane to the inside of the cell in opposite directions, and so that is what makes this an antiporter. Now it turns out that 3 sodium ions are going to be exported towards the outside of the cell, whereas 2 potassium ions are going to be imported towards the inside of the cell.

It has the n, it has the a, and it has the plus. And so this, because it has 3 characters can remind you that it's actually 3Na⁺ ions that are going to be exported towards the outside of the cell. And the Potassium symbol here has only 2 characters. So it has the k and it has the plus, and so that can help remind you that it's 2K⁺ ions that are being imported towards the inside of the cell. Now what can also help you remember that, Potassium are going to be imported towards the inside of the cell is to just think of a pumpkin.

Because if you think about a pumpkin, it'll tell you that the sodium-potassium pump is going to pump K⁺ into the cell. And so if you remember pump gen, you'll remember that, hey, potassium ions get pumped into the cell or imported into the cell. So let's take a look at our image down below to clear up some of this and notice that right here in the middle, embedded in this plasma membrane that we see right here, is the sodium-potassium pump right here. And notice that the sodium-potassium pump is going to take 3Na⁺ ions and those 3Na⁺ ions are going to be exported toward the outside of the cell. So notice the outside of the cell is up above on this side of the membrane, whereas the inside of the cell is down below.

So 3Na⁺ ions are going to be pumped or exported towards the outside of the cell. And if that continuously happens over and over again, then there's going to be a low concentration of sodium on the inside of the cell. So, remember the brackets here represent the concentration of sodium ions on the inside of the cell. It's going to be really really low if it keeps pumping them towards the outside, and of course, that means that on the outside over time there's going to be quite a high concentration of sodium ions on the outside of the cell. And as the sodium ions get pumped, of course, we know that potassium i