Video Transcript: A Tour of the Cell

Hi. It's Mr. Andersen and in this podcast I'm going to take you on a tour of the cell, we're going to talk about the different types of cells and then how the structures inside a cell fit their function. First thing, though, that we need to talk about is why cells are small reason cells are small, is the material moves into a cell through a process called diffusion. So oxygen gets in that way, and carbon dioxide is going to move out in the same way. And so it would take a long time for material to diffuse into a cell. And so what we can do is we can actually make that volume the same, but we can increase the surface area. And now the distance that material has to move is actually relatively small. And you also might think to yourself, Well, why aren't they infinitely small? Why are they really, really tiny? Well, the reason why is that the material inside a cell, the information inside the cell, like the DNA, and the machinery of the cell has to be able to fit inside the cell. And so there's like a perfect sweet spot in size for all the different types of cells that we have. Another thing I want to talk about is cells are not boring. When I grew up, I had this idea that a cell was like a bag of jelly, and you had stuff like a nucleus inside it, and it would essentially float around. This is probably perpetuated by biology teachers always assigning like an edible cell assignment. And if you actually look inside a cell, it's incredibly complex, they have this cytoskeleton it's made up of a number of different macromolecules. It's like a lattice inside the cell, and all the organelles fit within that lattice. And it works almost like a monorail as materials moved around on this monorail using these motor proteins. And I'm not joking, they literally walk like that on the on the monorail. And so they're incredibly complex cells are, but they're oftentimes misunderstood. And they were totally invisible to scientists until we invented the microscope. In other words, we couldn't see them. If you look at your hand, you can't see the cells. And scientists couldn't see me there. So they didn't know what was going on until they discovered and invented the microscope. The microscope comes in two different types. You basically have optical microscopes and then electron microscopes. Optical microscopes use light and lenses to magnify the image if you've ever used by an oculars. And then you turn it upside down and hold it close to your hand, you actually have a real simple microscope. And so that's the way that they work. If it's an electron microscope, what they're using is a number of magnets. And those magnets will be used to focus electrons, either through an image or bouncing it off an image. So we've got transmission and scanning electron microscopes.

How does this work? Well, a quick demo would be to take a big magnet and hold it really close to an old television or your computer screen, don't do this, if you were to do it, it would permanently ruin your monitor or your computer screen. But basically what it's doing is the magnet is changing the path of the electrons. And by doing that, we can actually increase the magnification on the specimen. So here's some pictures that were taken with these, this would be paramecium. With an optical electro optical microscope, one that you'd have in a typical biology classroom, these ones are taken by a transmission electron microscope, these are little viruses, or this would be an ant that you're looking at. Now these two are dead because of the material in order to look at it, the process is actually going to destroy it, in fact, and here you have to put a thin layer of metal on it that we can bounce it off on a scanning electron microscope. And so the future is electron microscopes, but it's also what are called fluorescent optical microscopes. So we're coming up with these beautiful fluorescent dyes, you saw one on the first page in this podcast, and that we can stain material that can stay alive. I even saw one stain this last summer that was a live dead stain. And so you would stain it and it would show you all the cells that were alive at that point and dead at that point. So really cool, we're getting some great visualized visualization of the cell.

First thing you should know is there are two major types of cells. We have what are called prokaryotic cells. And then eukaryotic cells. Prokaryotic cells are going to lack a nucleus. So there's going to be no nucleus. Eukaryotic cells are going to have a nucleus. What types of things are prokaryotic? Really only two things, bacteria are going to be prokaryotic. And then the Archaea bacteria are going to be prokaryotic. Eukaryotic are going to be things that you think of as alive that aren't microscopic. Things like plants, animals, fungus produce, things like that, that are really, really large. And the scale is bad here because if I were to scale it, right, the produce or excuse me, the bacteria would be about the size of this mitochondria. So these are really, really small, but there's some similarities between the two. In other words, all cells are going to have nucleic material. So they're gonna have DNA. All cells are going to have a cell membrane around the outside some form of cytosol on the inside, and they're also going to have ribosomes, man, they may differ, but all cells are going to have those things as we move to eukaryotic cells.

Let me go back again. Then we're going to have organelles. So we're going to have organs within the cell that you're familiar with, like a mitochondria would be an example of that. And so basically prokaryotic cells are simpler. I'll talk more though about them when I talk about bacteria. But most of the time in this podcast, I'm going to talk about eukaryotic cells. This would be an animal cell, I can tell right away. And so let's kind of look through an animal cell. So basically, these are the major organelles that are found within a cell, from the nucleus all the way down to the centriole. And so what I'm going to do is go through it, show you where they are, talk about what they do, and then you probably want to review at the end and go through all of them and see how much of the information that you actually picked up. So let's start with number one. And that's the nucleus. The nucleus is going to be found within the nucleus. And I used to be confused on how this actually works, what they do is all the chromosomes that are within the nucleus, what they do is they put all of their genes to make ribosomes in one area within the nucleus. And that as a result, since we have a lot of proteins inside here, is going to be a little darker when it gets stained. And so this is an area where the chromosomes are all producing ribosomal RNA to make the ribosomes gonna be right there.

It's kind of a two-step process. So basically, what happens is, in this area, they're going to produce ribosomal RNA, it'll roll out here to actually build some of the proteins using ribosomes outside of the cytoplasm, then those proteins will move back where we assemble the building blocks of proteins, which are going to be ribosomes. And so I talked about a lot of different things. But what did I mean to talk about? Well, the nucleolus is an area where the ribosomes are assembled inside the nucleus, if we go to the next one, next one is going to be the nucleus. And that's one of the first organelles that was ever discovered. There's a beautiful fluorescent dye on the nuclei. So what's the function of the nucleus? Well, when I grew up, I always heard it was like the brain of the cell, that's really over oversimplifying it, what's inside here, basically, we've got DNA, so the genetic material of the cell is going to be found inside the nucleus. And that's going to determine you know what kind of a cell it's going to become. But it also is going to control the cell. In other words, we're going to make proteins, we're going to make enzymes at a certain time. And as a result of that cell is going to do something. And so if you still want to think that it's the control center of the cell, that's okay. But a better way to think about it is just where the genetic material is. And it's also going to have little pores on the outside, that will become important when we start talking about transcription and translation, so there are going to be little holes on it. And that's how material can move out, and material can move in through those little holes.

Okay, next we get to the ribosomes, ribosome. Generally growing up, I represented those as little dots inside the cell; it's a little more complex than that, the two parts of it, you're gonna have a small subunit on the bottom, you're gonna have a large subunit on the top, and the messenger RNA is going to move through that. And then on the top, we're going to bring in the transfer RNA, and we're actually going to build our protein off of it. And so the function of the ribosomes is going to be to build proteins and prokaryotic. And eukaryotic have different ribosomes. And that's how some of our antibiotics actually work. vesicle is a broad term. vesicles basically means a membrane bound container. And they're really, really small. And sometimes they're really, really big. So a vacuole, the example of a vesicle. And they move material around depending on what they do like a transport vesicle would move material around, that's we get to the level of the rough ER, the rough endoplasmic reticulum, it's actually a membrane that's that is continuous with the nucleus.

And so we've got this folded membrane that comes out from the nucleus, you then have ribosomes that are sitting on the outside of it, and that's why it's called rough ER, I like to think of this as the factory inside of a cell. And so basically, what you're gonna have is this membrane, so you've got a membrane like this, and then you're just gonna have a ribosome that sits on the top of it. And so basically, what you can do is, as the messenger RNA comes through, we can make the proteins that we want to make. So it's like a factory, it's going to be where we make the material. It also produced the membranes that are going to be used within the cell.

Next, we get to the level the golgi body, I like to think it looks kind of like pita bread that is folded on top of itself. So if we were to say, where are these proteins going, they're going to be created in the endoplasmic reticulum. They'll then be packaged in a little transport vesicle and move to the Golgi apparatus. At the Golgi apparatus, we're going to modify that we're going to add things like carbohydrates to those proteins, we're going to snap them up a little bit, and then we're going to send them on their way. So another way to think about that is it's like a UPS. In other words, it is the shipping part of the cell. Things come in as a transport vesicle, they're gonna go out as a transport vesicle and they're gonna go where they need to go within the cell.

Next we got the cytoskeleton. The cytoskeleton is the structure inside the cell, it actually gives it that physical structure as it moves. If a cell were to move around, that's going to have to be like an amoeba that's going to do too, with the cytoskeleton as well. The way I like to think about this is through analogy, so it's kind of like a bridge. So on a bridge, you're going to have two things. Those are going to be supporting the bridge but then you're going to have these really thin wires that attach it up, like on the Golden Gate Bridge. And so basically inside a cell, we have those two things, we have the big things, those are called micro tubules. And they're made from protein called tubulin. And then we have these really thin things. And those are called micro filaments. And what the big things though microtubules do is they provide compressional support, just like the weight of the bridge is supported by them. And then those thin micro filaments are going to provide tensional support. And so if you think of a cell, like the Golden Gate Bridge, but kind of inverted inside it, that's a good way to think about what a cytoskeleton is.

Next, we get to the smooth endoplasmic reticulum; what's it missing ribosomes, what's it producing, it's going to produce a lot of the lipids, cholesterol, things like that in the cell. It also is really, really important in detoxification, so breaking down toxins. And so if you're an alcoholic, (hopefully not!) but if you're an alcoholic, basically, the more you drink, the more your body is going to build up smooth ER inside itself. So you're going to have to drink more and more and more and more.

Next, we've got the mitochondria. Mitochondria, you know, is the area where we're going to generate energy, what is really generating, that's going to be in the form of ATP. It basically has a folded membrane inside a membrane, it looks a lot like a bacteria. And that's because scientists think that they became parts of ourselves through endosymbiotic theory. In other words, they became parts of the cell, they produce ATP for that cell, and then they get a place to live. What's some evidence for that? Well, they have their own DNA they reproduce on their own through binary fission. And so it's pretty much accepted as biological fact.

Now we have the vacuole. The vacuole is going to be something that we find inside plants, not in animals, generally, large vacuoles. And in this plant cell here, what it's doing is it's, it's storing water. And so it stores that balance and pressure, that turgor pressure that keeps us out, properly inflated, some produce will actually have a contractile vacuole, that can pump water out when they're living in a freshwater environment as well. We've got vacuoles, but they're really small in general, and animals. And they're used for like endo- and exocytosis.

Next, we got the cytosol, the cytosol, you can think of as like the dissolve material. So it's the fluid, but it actually contains solutes inside it, we used to think that was about it. But what we're finding is they're concentration gradients within the cell. And so even the cytosol itself is pretty complex.

Next we go to the level of the lysosome. The lysosome is going to be sometimes it's been coined as like the suicide sack, what does it really have inside it, it has these digestive enzymes inside it, and it's contained within this membrane. And so basically, what we can do is we could have that go next to another vesicle, that has material that we want to break down. And those digestive enzymes will go in there and it'll break it down, or where it gets his name from as if we were to pop this lysosome. Basically, what happens is those digestive organ, digestive enzymes that go throughout the cell and would kill the cell, dissolve the cell. And so the process of apoptosis, where it cell kills itself is a product of lysosomes.

And finally, we have the centriole. centrioles part of what's called the central zone. And basically, it's important in positioning within the cell. So dependent upon where the centriole is, it's also going to set up where's the nucleus going to be and where the other parts of the cell going to be. It's also important as the cell divides, it's going to be as it migrates either side, it's going to initiate the formation of the spindle and the spindle is going to be attached to the chromosomes and you're going to pull it to either side. And so we have those, but if you're looking to higher plants, that's why they don't have centrioles. And their role is somewhat undefined. And I think we could say the same thing for all of these, that we really have an idea of what they do, but they probably do lots of other things that we're really not familiar with. And so this is where the podcast becomes scary. I'm going to make all those terms disappear. And basically, if you hit pause, could you go through at the beginning and list you know, what is number one? What is number two? What is the number three? What is the number four? What is number one do and if you can't do that you really don't understand it. And working with kids in class what I found that when you're trying to learn the parts of the cell, sometimes it's easier to just build some flashcards and go through the flashcards because if you can't get it right now then you don't got it. And so that's a tour of the cell and I hope it was fun. And I hope that was helpful.