It breaks up ATP into ADP and a phosphate group. So we say that sodium ions already have a higher concentration outside, but it keeps pumping them out. The sodium having a high, it establishes, it pumps sodium ions out of the cell against its concentration gradient. The sodium potassium pump, super important for establishing resting membrane voltage, I guess you could say resting membrane potential, but the concentration gradients it establishes are also very important. And the best case of this, if we're talking about animal cells, is the sodium potassium pump. So first let's talk about primary active transport, 'cause this might be a little bit more easy to think about. In active transport, we're either directly using energy to make something go against its gradient, or we're using some energy from a previous active transport to help facilitate something else going against this gradient. It's just about things flowing down their gradient. So passive transport doesn't require any energy to make this stuff happen. Here the sodium is high concentration outside, low concentration inside, and this happened because of the sodium potassium pump, but we're allowing it to now flow down its concentration gradient. ![]() You can see here, the sodium is going in, I'm sorry, the potassium is going in the direction of its concentration gradient, it's high concentration inside, low concentration outside, so we're allowing it to flow down the concentration gradient. But both of these, this is considered passive transport, it's facilitated diffusion, passive transport, we're allowing things to flow down their concentration gradient. Once the voltage hits a certain amount, then the channel opens, and then the sodium that has a higher concentration outside, can flow down its concentration gradient inside. And we see that when we talk about signals going down a neuron voltage gated channel. It's only going to be open if a certain trigger is hit. It's gonna be put in check because of its charge and its more positive outside and we'll talk about in other videos, but it's just a simple tunnel. We saw that with the potassium ion channels, where potassium builds up on the inside of the cell because of the sodium potassium pump, let me just be clear, down here this is the inside, this is the outside of the cell, and then but then these channels allow the potassium to flow down their concentration gradient. And one form of facilitated diffusion, Hey, just open up a tunnel and let things flow down their concentration gradient. We have a whole video on facilitated diffusion. Now the first type of help is just help to allow things to flow down their concentration gradient. But as we start to talk about things with more charge or things that might be larger then we're going to need some help. That will be able to diffuse down its concentration gradient through the cellular membrane. It's small, it doesn't have any charge, it has no polarity. And if you have a small enough molecule, let's say this is molecular oxygen. So perhaps the most basic, the most passive of the passive transports would be straight up diffusion. So let's talk about all of the different ways that molecules can be transported across a cellular membrane. I don't know if that is very clear, but here are some places where you can learn more about how cells perceive, integrate, and transmit information: For instance, a protein on the surface of the cell may detect signals from the surroundings and create a change in the inside of the cell, which generates a response such as activation of a transporter. ![]() Instead, cells have networks of molecules (mostly proteins) whose activity changes in response to cues. The way that cells perceive and regulate events around and inside them is not by conscious decision-making. They may even produce or not produce the transporter proteins (from the templates "written" in their DNA) depending on conditions. For instance, cells may activate or inactivate transporters depending on the conditions inside or outside of the cell. However, cells do have mechanisms to sense what is going on around and inside them and to regulate their internal processes. Cells don't have consciousness in the sense that you or I do.
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