Transcription
Okay, so in this video, we're going to talk about the slide here that reviews various different functions that proteins um play or jobs they they have in cells. So we're going to go through each diagram in turn and talk about what this cartoon is showing. Obviously, these are kind of cartoon diagrams. They're they're kind of showing simply what a protein does. This isn't an actual picture of a protein, obviously, this purple blob, but we now know that that purple blob is really a folded up chain of amino acids to create that shape.
Okay, so we'll start with this one here. So, uh, diagram A. Uh, in this example, take a quick look, see what you think is going on here. So if we think that this area here is a phospholipid bilayer, this would be our cell membrane. And you can look at the colors here, and that might make you think that this is the inside of the cell and this is the outside of the cell. And the outside the cell is watery, that's why it's kind of blue colored. Let me write that more clearly. Right. So I think in all these diagrams, we can assume the same kind of um convention is being used. This purple, this um yellow color down here is showing the in inner part of the cell, and then this is the phospholipid bilayer, the cell membrane. And then up here, this is the outside of the cell. All right.
So in this diagram A, we have a protein that is embedded in the membrane. And, uh, because you can see the purple is in sort of smooshed in here between the phospholipids. And this um protein seems to be transporting these yellow circles, whatever they might be, from the outside of the cell to the inside of the cell. Right, so we see them going through. So this protein is a transport protein or a channel. Right, we we we've looked at this before about how things cross the membrane. So one role of proteins is as, uh, transport proteins, uh, to move molecules across the membrane. And sometimes we call them channels, right?
Um, now a couple of things to notice on here. Number one is, um, this channel is obviously seems to be transporting yellow circles, whatever those yellow circles might be. Um, this channel would not work if it was blue squares, for example, or purple hexagons or something like that, right? So these channels are specific. They only work for the thing that they're designed for. There might be another channel that has a different shape opening here, maybe the opening is like this, and that would be able to transport blue squares, you know? But this is a so these protein channels or um transport proteins are specific. They allow, um, only one type of molecule in and out. And they can be, um, opened and closed. There there's control over, um, when the molecule can move in and when the molecule can move out. And you should know some of the molecules that would need transport because if you go back to that list that we learned earlier on in this unit, what molecules can and cannot cross the membrane with and without help? This would be the molecules that can't cross on their own. They need help. So things that have charges, like ions, or things that have that are larger with partial charges, like glucose molecules, that kind of stuff, they would all need this a transport protein. So this yellow circle could maybe be a potassium ion, or maybe it could be representing a glucose molecule. There's many things it could be, um, that that need help getting into the membrane. So that's a, um, acting like a transporter.
Let's do this one here. So if we look at B down here, what's going on here? Well, we can see a phospholipid membrane here. We can see another phospholipid membrane here. And we see, uh, an inside of a cell here and an inside of a cell here. And there's a little bit of blue sneaking in there, you can see. So this looks like it might be two cells, one cell like this and one cell like this. And they're coming up against each other. And the protein embedded in one cell membrane is talking or interfacing right here with the protein embedded in the neighboring cell membrane. And so that these proteins look like they're kind of locked together. This could be an example of proteins in in cell membranes acting like glue to, um, attach two cells to each other, like a connection between cell A and say cell B, kind of thing. So we could say that proteins might act a little bit like glue, maybe, or connectors, like, uh, jigsaw puzzle pieces. They're kind of connecting two cells together. This is the top cell goes around like this. The bottom cell is like this. And these two cells are kind of glued together by their interaction between their proteins.
Let's look at, uh, C, diagram C here. Uh, okay. So what have we got going on here? One, again, always, always stop and logically think through what you can see. So we can see cell membranes right here. This is the inside of the cell, and this is the outside of the cell because of the blue water we see. And, uh, we also see these yellow fibers. We should already know that this these are the fibers of the cytoskeleton. And then up here, we've got this long, all this stuff up here, feathery bits and long purpley bits. So from other diagrams, you should remember these. These are the cytoskeleton fibers down here, and this is the extracellular matrix, all this stuff up here. And this purple protein, it looks like it's connecting to the both the cytoskeleton and the extracellular matrix fibers. So this protein is acting like an anchor, like an anchor, like from a, I can't spell that. Hold on. Let's start, start again. Um, an anchor or an attachment point for these various pieces that are need to hold the cell and shape. So remember the cytoskeleton is like the tent poles inside of a tent. And when you have tent poles, usually they attach into a pocket or a little grommet, right? So they need something for them to attach to. That's what that protein is doing. Or the extracellular matrix, those are the bungee cords that stretch from one cell to the next. And they, and bungee cords need something to hook into. And they're hooking into, um, this protein right here. So this protein is acting like an attachment or anchor point for these various fibers on both the outside and the inside of the cell.
Um, let's look at this protein over here. So we're looking at D next. Uh, D. Okay. So we have our, this is the outside of the cell again, and this is the inside down here. And so, and here's our membrane. And so the proteins, there's one here and there's one here. They're side by side. And they are doing something on the inside of the cell here. So there's a, a yellow triangle. The yellow triangle looks like it slots in here, and then it comes out. If we follow the arrows, and it's turned into a blue square. And then the blue square slots in here, and then it gets spat out as a green circle. This is bizarre. Now, this is something we've not seen yet. We're going to get into this in unit 3 in more detail. But if I was to just, um, ignore these purple arrows and just say they're like turning a a yellow triangle into a blue square, that is how we would show a chemical reaction, right? Um, something turning into something else. And so what we're saying here is a chemical reaction that is being helped by the purple blob here, the protein in the membrane. So on its own, per orange, on its own, yellow triangles don't spontaneously turn into blue squares. But if you slot this yellow triangle into the protein, the protein can act on it in some way, and then it comes out as a blue square. So that protein is helping a chemical reaction to happen. And then the next protein in in the line, the second one here, this is turning a blue square into a green circle. Again, blue squares don't spontaneously turn into green circles. But if you slot them into this protein, the protein can do something and spit it back out differently. So these are proteins that are helping chemical reactions to occur, um, and we call these, uh, enzymes. They have a name, uh, and we're going to get into enzymes in the next unit. So but, um, proteins can act as enzymes, which are basically reaction helpers, molecules that help reactions to happen. So that's another job for enzymes.
I just glanced across and realized I'm running out of room, so I'm going to move myself over here since we're done with those diagrams and we can finish up. All right, so we've done A, B, C, D. Let's do, um, E next. So E is right here. So once again, let's orient ourselves. What are we looking at? Uh, so we've got a phospholipid bilayer here and a phospholipid bilayer here. And we've got an inside part of a cell here and we've got another inside cell here. And then here's the outside right here. All right, right. So once again, we've got a cell here and a cell here, and they're kind of coming together in this diagram. And you can see that we have a glycoprotein right here. Here's our protein part, and here's our glyco part. And it's interacting with this little piece here, like they fit together, right? So this is, um, receptors interacting with each other. Uh, this is the, this is the receptor, and this is its, um, a target molecule, a target that they're trying to talk to each other. So these proteins can act as receptors and signals. So I'm going to put that on there, a receptor and a signal. This is the receptor, and this is the kind of like the signal or what it's receiving, what's what's hooking into it right here. All right.
Um, last, last but not least, we'll do E and here's the la another example of how proteins jobs that proteins do. So this looks a lot like A is over here. Um, once again, we have the inside of the cell and the outside of the cell. And what we are doing is we're moving blue circles from the outside to the inside. Right, so A, this this A is basically the same as this A. It's showing a protein channel that can move a molecule across the membrane. And that blue circle could be lots of different things. We said ions, it could be glucose. Now, the only problem on this diagram, and I suddenly realized this, this arrow is facing the wrong way. So I'm going to put this arrow going this way. So it's not, textbooks don't get it right all the time. Sometimes they screw up, and this is a screw up. So let's focus on what's going on here in this diagram A. The blue circles are going from the outside to the inside. You can see the arrow is moving them this way, right? Okay. Um, and if we look at their concentration, there is more blue circles here, and there's less blue circles here. So the laws of diffusion would tell us that these blue circles, they want to go in this direction. They want to spread out. They want from where they're concentrated together, they want to spread to where there's less of themselves. And so this is an okay thing. They're going to want to go in this direction on their own. They don't have to be pushed. They just, this is just what they're naturally going to do because of diffusion. Now, that's all well and good in diagram A. But what if your body didn't want them to go in that direction? What if your body actually wanted to accumulate blue circles on the outside of the cells? All right, so they don't want it, they don't want them to come this way. They want them to go that way, to the outside. Now, they're not going to want to go that way on their own. That's opposite than what they want to do. They don't want to crowd together, they want to spread apart. But you want them to crowd together. And so in this diagram here, in part B, what we see here is this protein being used as a pump. It's actually forcing the blue circles out of the cell to to where they don't want to go. There's already a lot of blue circles on the outside, but we want to push even more there. We want to get them all out, kind of like bailing a boat, let's get it all out, right? So that's what this is symbolizing here. ATP means energy. So you can see this kind of flash of of energy here to make the mole, the blue molecules move in this direction. You have to force them. You've got to push them to go that way. And so this is, this B is different to this A. A doesn't have need any energy. They, these molecule, these blue circles will just go that direction on their own. So you don't have to force it. B is acting more like a pump, forcing the blue molecules where they don't want to go. So that's our last example of how proteins work. They can work as a pump, going against diffusion, forcing molecules to accumulate in a place.
So we got a long list here. Proteins can be transport proteins or channels. They can act like glue. They can be connectors or anchoring points. They can help reactions as in enzymes. Can be receptors. They can be signals. And they can act like a pump. All these are tools. And like I said before, we're trying to start thinking about proteins as tools that do jobs.