VIDEO: Understanding Cell Structure and Organelles

In this video we're going to take a little tour of the cell and talk about the function of the various organelles that are found in the cell. And to do that we're actually going to build sort of a picture of a cell as we go and identify the various organelles and their function along the way. And so I kind of encourage you, I mean you don't have to have amazing art skills here, but I would encourage you to kind of try to replicate what I'm doing here in your notes so that you have it available to you. So kind of first and foremost let's start with the boundary that separates the cell from the other external environment. So if this is a multicellular organism, this is what divides one cell from another. Or if this is a single cell organism, this is simply what's going to divide, keep that one cell separate from all of the outside world. So that barrier that is present in all types of organisms is something called a plasma membrane. So this plasma membrane, you can think about this just simply as, you know, the barrier. This is what separates the cell from everything else and allows it to control what's going on internally versus everything around it. Okay, so we have a plasma membrane that's present, and then in eukaryotic organisms another main feature is the presence of a nucleus. Okay, so a nucleus is also by a similar type of membrane. I'm kind of drawing mine as a dashed line because there's little holes in this membrane that allow for things to go in and out. Okay, but this right here is our nucleus and the nucleus's claim to fame is that this is where the DNA is stored, so the genetic information is stored in eukaryotic organisms. And so in eukaryotic organisms, this DNA is going to be present in the form of either a chromosome or chromatin. We'll talk about that in a later chapter. Right now we're just gonna go ahead and we're gonna draw ours as a chromosome, so put that right there. The chromosome is the structure that has the DNA bound on it. And another structure that is present on the inside is something called a nucleolus. And that's gonna be kind of drawn as a little bit darker. And our nucleolus on the inside is going to possess the information that we need to make ribosomes, which are one of our organelles that we'll identify in a minute. Okay, so in eukaryotic organisms on the interior of this plasma membrane we have an organelle called the nucleus. whose job is to store the DNA and keep it safe. And the DNA stays inside of the nucleus at all times. These little pores allow different molecules to come in and out to make copies of the DNA, so that the information that's coated on it can be used to build things like proteins. But the actual DNA stays safe inside of the nucleus. I mean, if you think about it, that's the master set of instructions for making all of these really important molecules. And so to ensure that it doesn't get damaged, we keep it kind of in this protective organelle. Now continuous with the nucleus is a very sort of long thin organelle, kind of goes back and forth, but as you can see is is one with the nucleus, the interior of the nucleus and those pores kind of open up to this structure. This structure is called the endoplasmic reticulum, and we'll identify that in a second, but really there's sort of two components to the endoplasmic reticulum. Some of the endoplasmic reticulum looks rough and is studded with these little tiny organelles called ribosomes. So ribosomes can exist sort of in two states. Ribosomes can either be free-floating or they can be bound to the surface of something. Okay, so here I'm drawing my ribosomes as these little blue circles. I'm gonna draw them off over here, and I've drawn both some free and bound ribosomes, but the function of a ribosome is that this is where proteins are manufactured. So that's just kind of the general function of a ribosome in general is that this is where we build proteins. Now, like I said, there's two different kinds of ribosomes. There are the free ribosomes. Those are the ones that are not attached to anything, right? So that would be these guys right here. And the free ribosomes are where proteins that stay in the cell are mainly built. So the individual cells are going to need proteins to complete their functions, and where the proteins that the cell is going to use are mainly built are in these free floating ribosomes. And then the bound ribosomes, and they can either be bound to the surface of the nucleus or they can be bound to the endoplasmic reticulum, the bound ribosomes, right, these are going to be where the proteins for export are mainly built. So these are going to be the proteins that the cell secretes, and then in a multicellular organism they're going to go to somewhere else in that organism. So now that then kind of leads to two different sections of the endoplasmic reticulum. The endoplasmic reticulum is this red structure that I've drawn, but you can see that part of the endoplasmic reticulum has these ribosomes attached, and we have some endoplasmic reticulum that is lacking, right? So in general, they are both collectively called the endoplasmic reticulum, and we call that the ER, okay, as short. So the general function of the endoplasmic reticulum is manufacturing. This is where a whole bunch of different types of molecules are built that are either going to stay in the cell or, like I said kind of earlier, they're going to be exported to somewhere else in the body. And so we have two different types of the endoplasmic reticulum. That's kind of our... we'll do this in both so that we can kind of keep track of what's going on here. We have the rough ER. the rough endoplasmic reticulum. So that is going to be the studded part. These are the ones that possess ribosomes that are attached. And again, kind of what we said, the claim to fame here is that this is where proteins that will be excreted are built. So the this is where the proteins that are eventually going to be sent somewhere else are made. And then for the smooth endoplasmic reticulum, these would be, this is the ER that is lacking ribosomes. This is going to be where lipids are produced, right? So that's going to include things like the sterols, the hormones, phospholipids, even fats, okay, potentially, some fatty acids will be produced, okay? So think, like, cells that produce a lot of hormones would have a lot of smooth ER. This is also responsible for sort of detox of harmful substances. So for instance, there's a lot of smooth ER in the liver, whose job is to break down harmful things that you might consume and sort of turn them into a safer, more soluble version. So the smooth ER would do this by tacking on different kinds of functional groups, like for instance, adding on a hydroxide group to a molecule, and that hydroxide group might make it more soluble in water, which might make it easier for the body to flush out. Okay, so Both of them are kind of in the business more or less of manufacturing. It's kind of like a very broad word for what they do, but they're making different kinds of things. The rough ER is really sort of in the business of making proteins, specifically proteins that are generally going to be sent to somewhere else. And then the smooth ER is responsible for making lipids. And kind of its other big claim to fame is that it's helping break down things that are harmful so that they can be excreted by the body. And I'm actually gonna I'm going to scooch over this line just a crisp midget so that I have a little more room here to add in. my next organelle. So the next organelle that we're going to talk about here is something called the Golgi apparatus. Let's do that in like an orangish color. At some point we're going to run out of colors here, but we'll keep with it for now. So the Golgi apparatus kind of looks like, I don't know, the way that I've seen it described in books is it looks like a stack of pita bread or pancakes that are kind of like in a row. Okay, so this right here is our Golgi apparatus. The function of the Golgi apparatus is to, I guess, think about if the endoplasmic reticulum is in charge of manufacturing, then the Golgi apparatus is in charge of basically like shipping and handling. Okay, so what it's going to do is it's going to receive the products of the ER, whether that's the smooth ER or the rough ER. It's going to modify those products as needed. So it might add on different functional groups, right? Not all that different than after a good has been manufactured. A lot of times tags and different kinds of warning labels will be added on. Kind of think that... the Golgi apparatus is kind of doing that by adding on different functional groups. And then ultimately, it might store those products temporarily, and then sort of ship them to their final destination. And that final destination could be somewhere within the cell, or it could be somewhere out of the cell. And it does that by using these little membrane-bound vehicles called vesicles. So these little membrane-bound vesicles are basically just little, I guess, compartments that they use to move things around throughout the cell. And so this particular vesicle, right, if we're kind of outlining the the pathway through which things could move, we could have something coming either from the rough ER or from the smooth ER. Heck, we could even have something come from a bound ribosome if we wanted. And that product is going to transgress through the Golgi apparatus and at the end it will pinch off into this vesicle. And that vesicle could then either go to the cell membrane and fuse with it, and if it does, then whatever that product is is going to be released from the cell and from there can go somewhere else in the body. Or it could go to another organelle where those products might be needed. Okay, so it just depends. Ultimately what we just described, that pathway, is something called the endomembrane system. So the endomembrane system sort of outlines the pathway through which items are manufactured, molecules are manufactured in the cell, and then ultimately sent to their destination. So remember, manufacturing happens in either the smooth ER generally or in the rough ER. This is the one main component of the endoplasmic reticulum. So this part is in charge of manufacturing. And then those manufactured goods, regardless of what we're making and where it's made, those are going to the Golgi apparatus. The Golgi apparatus will store, modify, and then ultimately a vesicle. is going to print off the Golgi apparatus and travel to the final destination. That final destination could be to somewhere in the cell. So it could be going to an organelle within the cell, or it could go to the cell membrane. the plasma membrane, and if it goes to the plasma membrane, then it is going out of the cell to somewhere else in the organism. But the various things that the cell produces generally follow sort of that pathway. All right, so let's kind of keep moving on along. So one other function that's pretty critical is the ability to break things down. So we have sort of two different, we have two different entities. in an animal cell that can do this. And the first one that we're going to look at is something called a lysosome. Let's pick kind of like a dark blue for this. It's kind of just a nice circular organelle. We'll bring it out over here. So the lysosome, the job of the lysosome is that, you know, it contains enzymes that are going to digest molecules. And kind of as a rule of thumb, the interior of the lysosomes is usually a pretty acidic interior. So kind of think almost like a similar type of function to your stomach. Your stomach is also a very acidic environment. And one of the jobs of your stomach is to help digest and break down the various macromolecules that you eat. So I guess the lysosome is kind of like a stomach of your cell, if you want to think about it that way. It's digesting some macromolecules with enzymes that are held within it. And actually, some single-celled organisms basically utilize this like their stomach. For instance, some amoebas, what they'll do is they will engulf something via something called phagocytosis. And when they engulf it, the thing that they wrap around merges with this lysosome, and that's where it sort of dissembles the food and digests it, again, like a stomach. Likewise, within our body, we have white blood cells who are trolling around and looking for foreign material that might be harmful to us. And similarly, if a white blood cell engulfs something foreign, like a bacterium or something else, then it can fuse with this lysosome to break that down and dissemble it. So the lysosome is kind of like the stomach, I guess, of the cell. It's breaking down some of these macromolecules, kind of along the lines of breaking down. And we're not going to go into as much detail because the function of this is a lot broader, and so it's kind of hard to just give like a very unified description of what it does. But another similar looking organelle is something called a peroxisome. The peroxisome is likewise kind of in the business of breaking down things, especially things that might be harmful. I guess one thing that kind of differentiates itself is that in the process of breaking down, it's also producing peroxide. So a lot of the times the way that it's breaking down or neutralizing something particularly something that could be harmful is by transferring one of the hydrogens from that molecule to some oxygens to create peroxide. So if you just know that it breaks down things and that along the way it produces peroxide, that will be enough for our class. All right, so let's kind of go up here now as we continue our tour. We're almost done kind of looking at few features that would be sort of Somewhat similar between types of cells. Everything that we've shown here would be present in both an animal or a plant cell except the lysosome. So maybe make a little note to yourself, right? The lysosome is found only in animal cells. But so far everything else that we have highlighted would likewise be found in a plant cell. And we'll add some features that are exclusive to plant cells in a minute, okay? All right, so kind of continuing on our tour, the next one that we are going to add, and if it helps you, by the way, if it helps you kind of put like brackets around here of similar types of functions, I mean basically lysosomes and peroxisomes are similar because they both are breaking down substances. All right. The next really important organelle that's present in both plants and animals is something called a mitochondria. So mitochondria have two membranes, an inner membrane which is highly folded, that's what I'm drawing right now. We'll talk about this in chapter five. And then an outer membrane that's a little bit smoother. So this is our mitochondria. The mitochondria's job, this is where cellular respiration occurs. And what that's going to do for the cell is cellular respiration is going to convert energy in macromolecules that we eat, or in the case of a plant that they fix via photosynthesis, they're going to convert the molecule that are stored in the macromolecules into ATP. So basically what it's going to do is it's going to generate ATP. usable energy from molecules. It's not creating energy, so kind of note the word convert. There is energy stored in the various molecules that we consume. And so what this little organelle is doing is it's converting that stored energy into a usable form of energy, which is ATP, which is really critical to survival. And then there's just one last organelle that we are going to look at and then we'll kind of look at the plant and see if the features that are unique to it, and that is the cytoskeleton. So the cytoskeleton is kind of throughout this whole deal. Think of it like as a network of embedded fibers. And if you read the book, there's all different kinds of fibers that make up the cytoskeleton that differ in size and their specific function. But we're just going to very generally label the cytoskeleton. The cytoskeleton is, you can think of it as a whole sort of web of fibers, and those fibers have some specific functions. One of them is structure, so kind of think of them almost like as rebarb, I guess. They're help providing some structure to the organism, and they can also help with movement. Some organisms will have... cytoskeleton fibers on the exterior in the form of flagella or cilia, which helps them like literally swim around in water. But even within the cell, you can think of these as almost like train tracks for the organelles. So essentially, organelles can travel along these cytoskeleton fibers, kind of like train tracks or a rail. and move throughout the cell. And all of this, by the way, is floating around in a fluid called the cytoplasm. So there's really no way to draw that because it's everything that this is in, but I guess if you kind of want to put that off to the side, the cytoplasm, that is the fluid on the interior of the cell. And that ultimately is what all of these things are embedded in. Okay. All right. So with that in mind, now that we have some pretty good notes on those organelles, let's kind of go down to our plant cell. And I already have in the plant cell a lot of the features that we have up here, right? Notice that one feature that I did not draw was there is no lysosome, right? Because there aren't lysosomes in plant cells. But there are some additional features that are present in here. that are not present in the animal cell that we've talked about kind of already, but we're going to go ahead and add them and talk about their function. One of them is an organelle called a chloroplast. So the chloroplast has an outer membrane and then it has these little tiny membrane-bound sacs on the inside. The job of the chloroplast is to convert light energy into stored chemical energy. So, and this is stored in sugars. So this is where photosynthesis occurs. That's the process that we're talking about here. One minute, it's a little messy. Give me a second. So the chloroplast is unique to plant cells and some protists, but they're not found in animal cells, and it has sort of a similar type of function to the mitochondria. These two organelles together are kind of in the business of energy conversion. So they're kind of like the electric plants of your cells. We can't create energy, that's something we're going to talk about in a later chapter, but we can convert energy from one format to another, and that's what these two organelles do. The mitochondria is found in both plants and animal cells. The chloroplast is only found in animal cells and some protists. Another organelle that we find in Plant cells but not so much in animal cells is a very large vacuole called the central vacuole. There are some types of vacuoles in animal cells but there isn't a central vacuole. The central vacuole has a couple of different jobs. This is where some things are stored, so storage is kind of one function. A lot of water is going to be in here. The plant will break down some wastes in the central vacuole. And also, this is basically helping with the structure of the cell, something we'll talk more about later in this chapter when we talk about osmosis. Okay, so what ends up happening is that when this central vacuole gets big, and when it fills with water, the water pressure on the inside is high enough against it that it actually pushes on the sides of the cell, and that's what helps kind of provide structure to non-woody plants so that they can stand upright. So that's one reason why your plants wilt when you don't water them. If you fail to water them, then the amount of water in this central vacuole decreases and it loses some of that pressure and therefore some of the structure, and so that's what causes the wilting in the non-woody plants. And then finally, the last structure that we're going to focus on that's kind of unique to the plant cell is that they have a rigid exterior on the outside of their plasma membrane, and this rigid exterior is called the cell wall. So let's go ahead and add it here. It has usually very angular edges. It's made up primarily of a polysaccharide called cellulose. There we go. So we have this cell wall and the cell wall's function is structure. So it provides structure to the plant and is a lot more robust than the cell membrane. Note that the animal, the plant cell, also has a plasma membrane, right? So the plasma membrane is present in both. The difference is that the plants also have at least one cell wall on the exterior of that plasma membrane. And we'll actually talk in class sometimes they have more than one cell wall, but at the very minimum they have one cell wall on the exterior of the plasma membrane that sort of gives them rigidity and structure. So I guess structures that we see only in plants that we're focusing on because we we have up here the the only in animals, right? So the only implants that we're focusing on here would be the chloroplast, the central vacuole. Just make a note that you can have vacuoles in animal cells, but they don't have central vacuoles. And then the cell wall. But the other components are common between the two types and have the same general functions. So those are all of the organelles that we are focusing on. Make sure that you sort of know what organelles participate in the endomembrane system, and that you know the function of the various organelles that we outlined in this video.

So kind of first and foremost let's start with the boundary that separates the cell from the other external environment. So if this is a multicellular organism, this is what divides one cell from another. Or if this is a single cell organism, this is simply what's going to divide, keep that one cell separate from all of the outside world. So that barrier that is present in all types of organisms is something called a plasma membrane. So this plasma membrane, you can think about this just simply as, you know, the barrier.

This is what separates the cell from everything else and allows it to control what's going on internally versus everything around it. Okay, so we have a plasma membrane that's present, and then in eukaryotic organisms another main feature is the presence of a nucleus. Okay, so a nucleus is also by a similar type of membrane. I'm kind of drawing mine as a dashed line because there's little holes in this membrane that allow for things to go in and out. Okay, but this right here is our nucleus and the nucleus's claim to fame is that this is where the DNA is stored, so the genetic information is stored in eukaryotic organisms.

And so in eukaryotic organisms, this DNA is going to be present in the form of either a chromosome or chromatin. We'll talk about that in a later chapter. Right now we're just gonna go ahead and we're gonna draw ours as a chromosome, so put that right there. The chromosome is the structure that has the DNA bound on it.

And another structure that is present on the inside is something called a nucleolus. And that's gonna be kind of drawn as a little bit darker. And our nucleolus on the inside is going to possess the information that we need to make ribosomes, which are one of our organelles that we'll identify in a minute.

Okay, so in eukaryotic organisms on the interior of this plasma membrane we have an organelle called the nucleus. whose job is to store the DNA and keep it safe. And the DNA stays inside of the nucleus at all times. These little pores allow different molecules to come in and out to make copies of the DNA, so that the information that's coated on it can be used to build things like proteins.

But the actual DNA stays safe inside of the nucleus. I mean, if you think about it, that's the master set of instructions for making all of these really important molecules. And so to ensure that it doesn't get damaged, we keep it kind of in this protective organelle. Now continuous with the nucleus is a very sort of long thin organelle, kind of goes back and forth, but as you can see is is one with the nucleus, the interior of the nucleus and those pores kind of open up to this structure. This structure is called the endoplasmic reticulum, and we'll identify that in a second, but really there's sort of two components to the endoplasmic reticulum.

Some of the endoplasmic reticulum looks rough and is studded with these little tiny organelles called ribosomes. So ribosomes can exist sort of in two states. Ribosomes can either be free-floating or they can be bound to the surface of something. Okay, so here I'm drawing my ribosomes as these little blue circles.

I'm gonna draw them off over here, and I've drawn both some free and bound ribosomes, but the function of a ribosome is that this is where proteins are manufactured. So that's just kind of the general function of a ribosome in general is that this is where we build proteins. Now, like I said, there's two different kinds of ribosomes. There are the free ribosomes. Those are the ones that are not attached to anything, right?

So that would be these guys right here. And the free ribosomes are where proteins that stay in the cell are mainly built. So the individual cells are going to need proteins to complete their functions, and where the proteins that the cell is going to use are mainly built are in these free floating ribosomes. And then the bound ribosomes, and they can either be bound to the surface of the nucleus or they can be bound to the endoplasmic reticulum, the bound ribosomes, right, these are going to be where the proteins for export are mainly built.

So these are going to be the proteins that the cell secretes, and then in a multicellular organism they're going to go to somewhere else in that organism. So now that then kind of leads to two different sections of the endoplasmic reticulum. The endoplasmic reticulum is this red structure that I've drawn, but you can see that part of the endoplasmic reticulum has these ribosomes attached, and we have some endoplasmic reticulum that is lacking, right? So in general, they are both collectively called the endoplasmic reticulum, and we call that the ER, okay, as short.

So the general function of the endoplasmic reticulum is manufacturing. This is where a whole bunch of different types of molecules are built that are either going to stay in the cell or, like I said kind of earlier, they're going to be exported to somewhere else in the body. And so we have two different types of the endoplasmic reticulum. That's kind of our... we'll do this in both so that we can kind of keep track of what's going on here.

We have the rough ER. the rough endoplasmic reticulum. So that is going to be the studded part. These are the ones that possess ribosomes that are attached. And again, kind of what we said, the claim to fame here is that this is where proteins that will be excreted are built.

So the this is where the proteins that are eventually going to be sent somewhere else are made. And then for the smooth endoplasmic reticulum, these would be, this is the ER that is lacking ribosomes. This is going to be where lipids are produced, right? So that's going to include things like the sterols, the hormones, phospholipids, even fats, okay, potentially, some fatty acids will be produced, okay?

So think, like, cells that produce a lot of hormones would have a lot of smooth ER. This is also responsible for sort of detox of harmful substances. So for instance, there's a lot of smooth ER in the liver, whose job is to break down harmful things that you might consume and sort of turn them into a safer, more soluble version.

So the smooth ER would do this by tacking on different kinds of functional groups, like for instance, adding on a hydroxide group to a molecule, and that hydroxide group might make it more soluble in water, which might make it easier for the body to flush out. Okay, so Both of them are kind of in the business more or less of manufacturing. It's kind of like a very broad word for what they do, but they're making different kinds of things.

The rough ER is really sort of in the business of making proteins, specifically proteins that are generally going to be sent to somewhere else. And then the smooth ER is responsible for making lipids. And kind of its other big claim to fame is that it's helping break down things that are harmful so that they can be excreted by the body. And I'm actually gonna I'm going to scooch over this line just a crisp midget so that I have a little more room here to add in. my next organelle.

So the next organelle that we're going to talk about here is something called the Golgi apparatus. Let's do that in like an orangish color. At some point we're going to run out of colors here, but we'll keep with it for now. So the Golgi apparatus kind of looks like, I don't know, the way that I've seen it described in books is it looks like a stack of pita bread or pancakes that are kind of like in a row.

Okay, so this right here is our Golgi apparatus. The function of the Golgi apparatus is to, I guess, think about if the endoplasmic reticulum is in charge of manufacturing, then the Golgi apparatus is in charge of basically like shipping and handling. Okay, so what it's going to do is it's going to receive the products of the ER, whether that's the smooth ER or the rough ER.

It's going to modify those products as needed. So it might add on different functional groups, right? Not all that different than after a good has been manufactured.

A lot of times tags and different kinds of warning labels will be added on. Kind of think that... the Golgi apparatus is kind of doing that by adding on different functional groups. And then ultimately, it might store those products temporarily, and then sort of ship them to their final destination.

And that final destination could be somewhere within the cell, or it could be somewhere out of the cell. And it does that by using these little membrane-bound vehicles called vesicles. So these little membrane-bound vesicles are basically just little, I guess, compartments that they use to move things around throughout the cell. And so this particular vesicle, right, if we're kind of outlining the the pathway through which things could move, we could have something coming either from the rough ER or from the smooth ER. Heck, we could even have something come from a bound ribosome if we wanted.

And that product is going to transgress through the Golgi apparatus and at the end it will pinch off into this vesicle. And that vesicle could then either go to the cell membrane and fuse with it, and if it does, then whatever that product is is going to be released from the cell and from there can go somewhere else in the body. Or it could go to another organelle where those products might be needed.

Okay, so it just depends. Ultimately what we just described, that pathway, is something called the endomembrane system. So the endomembrane system sort of outlines the pathway through which items are manufactured, molecules are manufactured in the cell, and then ultimately sent to their destination. So remember, manufacturing happens in either the smooth ER generally or in the rough ER. This is the one main component of the endoplasmic reticulum.

So this part is in charge of manufacturing. And then those manufactured goods, regardless of what we're making and where it's made, those are going to the Golgi apparatus. The Golgi apparatus will store, modify, and then ultimately a vesicle.

is going to print off the Golgi apparatus and travel to the final destination. That final destination could be to somewhere in the cell. So it could be going to an organelle within the cell, or it could go to the cell membrane.

the plasma membrane, and if it goes to the plasma membrane, then it is going out of the cell to somewhere else in the organism. But the various things that the cell produces generally follow sort of that pathway. All right, so let's kind of keep moving on along. So one other function that's pretty critical is the ability to break things down.

So we have sort of two different, we have two different entities. in an animal cell that can do this. And the first one that we're going to look at is something called a lysosome.

Let's pick kind of like a dark blue for this. It's kind of just a nice circular organelle. We'll bring it out over here.

So the lysosome, the job of the lysosome is that, you know, it contains enzymes that are going to digest molecules. And kind of as a rule of thumb, the interior of the lysosomes is usually a pretty acidic interior. So kind of think almost like a similar type of function to your stomach. Your stomach is also a very acidic environment. And one of the jobs of your stomach is to help digest and break down the various macromolecules that you eat.

So I guess the lysosome is kind of like a stomach of your cell, if you want to think about it that way. It's digesting some macromolecules with enzymes that are held within it. And actually, some single-celled organisms basically utilize this like their stomach. For instance, some amoebas, what they'll do is they will engulf something via something called phagocytosis. And when they engulf it, the thing that they wrap around merges with this lysosome, and that's where it sort of dissembles the food and digests it, again, like a stomach.

Likewise, within our body, we have white blood cells who are trolling around and looking for foreign material that might be harmful to us. And similarly, if a white blood cell engulfs something foreign, like a bacterium or something else, then it can fuse with this lysosome to break that down and dissemble it. So the lysosome is kind of like the stomach, I guess, of the cell. It's breaking down some of these macromolecules, kind of along the lines of breaking down.

And we're not going to go into as much detail because the function of this is a lot broader, and so it's kind of hard to just give like a very unified description of what it does. But another similar looking organelle is something called a peroxisome. The peroxisome is likewise kind of in the business of breaking down things, especially things that might be harmful.

I guess one thing that kind of differentiates itself is that in the process of breaking down, it's also producing peroxide. So a lot of the times the way that it's breaking down or neutralizing something particularly something that could be harmful is by transferring one of the hydrogens from that molecule to some oxygens to create peroxide. So if you just know that it breaks down things and that along the way it produces peroxide, that will be enough for our class. All right, so let's kind of go up here now as we continue our tour. We're almost done kind of looking at few features that would be sort of Somewhat similar between types of cells.

Everything that we've shown here would be present in both an animal or a plant cell except the lysosome. So maybe make a little note to yourself, right? The lysosome is found only in animal cells.

But so far everything else that we have highlighted would likewise be found in a plant cell. And we'll add some features that are exclusive to plant cells in a minute, okay? All right, so kind of continuing on our tour, the next one that we are going to add, and if it helps you, by the way, if it helps you kind of put like brackets around here of similar types of functions, I mean basically lysosomes and peroxisomes are similar because they both are breaking down substances. All right. The next really important organelle that's present in both plants and animals is something called a mitochondria.

So mitochondria have two membranes, an inner membrane which is highly folded, that's what I'm drawing right now. We'll talk about this in chapter five. And then an outer membrane that's a little bit smoother.

So this is our mitochondria. The mitochondria's job, this is where cellular respiration occurs. And what that's going to do for the cell is cellular respiration is going to convert energy in macromolecules that we eat, or in the case of a plant that they fix via photosynthesis, they're going to convert the molecule that are stored in the macromolecules into ATP. So basically what it's going to do is it's going to generate ATP.

usable energy from molecules. It's not creating energy, so kind of note the word convert. There is energy stored in the various molecules that we consume. And so what this little organelle is doing is it's converting that stored energy into a usable form of energy, which is ATP, which is really critical to survival.

And then there's just one last organelle that we are going to look at and then we'll kind of look at the plant and see if the features that are unique to it, and that is the cytoskeleton. So the cytoskeleton is kind of throughout this whole deal. Think of it like as a network of embedded fibers.

And if you read the book, there's all different kinds of fibers that make up the cytoskeleton that differ in size and their specific function. But we're just going to very generally label the cytoskeleton. The cytoskeleton is, you can think of it as a whole sort of web of fibers, and those fibers have some specific functions. One of them is structure, so kind of think of them almost like as rebarb, I guess. They're help providing some structure to the organism, and they can also help with movement.

Some organisms will have... cytoskeleton fibers on the exterior in the form of flagella or cilia, which helps them like literally swim around in water. But even within the cell, you can think of these as almost like train tracks for the organelles. So essentially, organelles can travel along these cytoskeleton fibers, kind of like train tracks or a rail. and move throughout the cell.

And all of this, by the way, is floating around in a fluid called the cytoplasm. So there's really no way to draw that because it's everything that this is in, but I guess if you kind of want to put that off to the side, the cytoplasm, that is the fluid on the interior of the cell. And that ultimately is what all of these things are embedded in.

Okay. All right. So with that in mind, now that we have some pretty good notes on those organelles, let's kind of go down to our plant cell.

And I already have in the plant cell a lot of the features that we have up here, right? Notice that one feature that I did not draw was there is no lysosome, right? Because there aren't lysosomes in plant cells.

But there are some additional features that are present in here. that are not present in the animal cell that we've talked about kind of already, but we're going to go ahead and add them and talk about their function. One of them is an organelle called a chloroplast.

So the chloroplast has an outer membrane and then it has these little tiny membrane-bound sacs on the inside. The job of the chloroplast is to convert light energy into stored chemical energy. So, and this is stored in sugars.

So this is where photosynthesis occurs. That's the process that we're talking about here. One minute, it's a little messy.

Give me a second. So the chloroplast is unique to plant cells and some protists, but they're not found in animal cells, and it has sort of a similar type of function to the mitochondria. These two organelles together are kind of in the business of energy conversion.

So they're kind of like the electric plants of your cells. We can't create energy, that's something we're going to talk about in a later chapter, but we can convert energy from one format to another, and that's what these two organelles do. The mitochondria is found in both plants and animal cells. The chloroplast is only found in animal cells and some protists.

Another organelle that we find in Plant cells but not so much in animal cells is a very large vacuole called the central vacuole. There are some types of vacuoles in animal cells but there isn't a central vacuole. The central vacuole has a couple of different jobs.

This is where some things are stored, so storage is kind of one function. A lot of water is going to be in here. The plant will break down some wastes in the central vacuole. And also, this is basically helping with the structure of the cell, something we'll talk more about later in this chapter when we talk about osmosis.

Okay, so what ends up happening is that when this central vacuole gets big, and when it fills with water, the water pressure on the inside is high enough against it that it actually pushes on the sides of the cell, and that's what helps kind of provide structure to non-woody plants so that they can stand upright. So that's one reason why your plants wilt when you don't water them. If you fail to water them, then the amount of water in this central vacuole decreases and it loses some of that pressure and therefore some of the structure, and so that's what causes the wilting in the non-woody plants. And then finally, the last structure that we're going to focus on that's kind of unique to the plant cell is that they have a rigid exterior on the outside of their plasma membrane, and this rigid exterior is called the cell wall. So let's go ahead and add it here.

It has usually very angular edges. It's made up primarily of a polysaccharide called cellulose. There we go.

So we have this cell wall and the cell wall's function is structure. So it provides structure to the plant and is a lot more robust than the cell membrane. Note that the animal, the plant cell, also has a plasma membrane, right? So the plasma membrane is present in both. The difference is that the plants also have at least one cell wall on the exterior of that plasma membrane.

And we'll actually talk in class sometimes they have more than one cell wall, but at the very minimum they have one cell wall on the exterior of the plasma membrane that sort of gives them rigidity and structure. So I guess structures that we see only in plants that we're focusing on because we we have up here the the only in animals, right? So the only implants that we're focusing on here would be the chloroplast, the central vacuole. Just make a note that you can have vacuoles in animal cells, but they don't have central vacuoles.

And then the cell wall. But the other components are common between the two types and have the same general functions. So those are all of the organelles that we are focusing on.

Make sure that you sort of know what organelles participate in the endomembrane system, and that you know the function of the various organelles that we outlined in this video.

Transcript for:VIDEO: Understanding Cell Structure and Organelles

Transcript for:
VIDEO: Understanding Cell Structure and Organelles