 We're going to talk about both proteins that carry out facilitated diffusion or enable facilitated diffusion. We're going to talk about them with this same picture. So all the notes are going on this one page. But we're going to start out talking about channels. And there are channels and carriers illustrated in this diagram. So take a second, push pause if you need to, to make a guess. Which one of these is a channel or are channels? And hopefully you look at this and you go, like, dude, doesn't it kind of look like a little tunnel through the cell membrane? That's what a channel is. It is a tunnel, but it's a really specific tunnel. So channels only allow certain molecules through. An example of a channel that, oh my goodness, the sodium channel and the potassium channel. These are examples. We have calcium channels. We have glucose channels. We have iodine channels. We have bajillions of different kinds of channels. Potassium channels and potassium channels, I think, are super interesting. They enable neural function. So I'm talking to you right now because of the amazing capacities of my sodium and potassium channels. Channels let their specific molecule through down a concentration gradient. In this case, we have little pink dots. Do you see all my little pink dots? And I don't know, we could count up to determine the concentration gradient, but I'm just going to tell you that the concentration gradient of pink dots is into the cell. There are more pink dots outside of the cell than inside of the cell, which means there's a concentration gradient to the pink dots are going to want to move in. How are they going to get through? For whatever reason, they can't get through the cell membrane. So they need that channel to provide the route. The channel, because of its magical properties, not magical chemical, it's 100%, the protein is structured in a way that only allows that certain pink molecule to travel through it down its concentration gradient. You can have gated channels where the gate will open in certain circumstances. Sometimes a gated channel is a mechanical channel, so if you push on the channel or apply pressure, that will pop the channel open and then the ions can move. Other channels are voltage gated, so an electrical shock can cause the channels to open. That allows the cell to pick and choose when and how stuff is going to get through. I think what I'll just say is that the qualities of these channels are really, really, really specific, and I think that's it. Let's talk about the carriers next.