In this video we're going to do a basic review of the cell and the things inside of the cell like the organelles, the tiny organs of the cell. So first we have the nucleus which is right there and the nucleus is basically the command and control center of the cell. It tells the cell what to do, how to grow, what proteins to make, what lipids to produce and things like that. Now in the nucleus in this region you have long strands of DNA known as chromatin.
And the DNA is basically the instruction manual or the blueprint of the cell. It stores the genetic information of the cell. And so within the DNA you have the instructions on how to make the proteins, how to make the individual organelles of the cell, and what they need to do. Now inside of the nucleus we have this base, this bar right here, and that is the nucleolus. Now the nucleolus, it creates ribosomal RNA to make ribosomes.
And ribosomes, you can see these little spheres floating in the cytosol. And the ribosomes, they make proteins. Now the ribosomes consist of ribosomal RNA and proteins. But they manufacture proteins. Now the way the nucleus makes proteins is that...
It sends mRNA or messenger RNA which carries the instructions to the ribosome to make the specific type of protein that's needed for the cell. Now the nucleus is surrounded by a membrane known as the nuclear envelope and on this membrane you'll find these holes on it which are known as nuclear pores and they allow stuff to go into and out of the cell. So the messenger RNA comes out of the nucleus through those nuclear pores.
Now let's talk about the ER, the endoplasmic reticulum. There are two types. The first one is the rough ER, which is all of this in that region.
And the second is the smooth ER, which is right here. Now, what do you notice about these two? What is the difference between them? The rough ER contains ribosomes.
The smooth ER does not contain any ribosomes. So the rough ER, it assists in the production of proteins because ribosomes, that's what they do, they make proteins. Because the smooth ER doesn't have any ribosomes, it does not make any proteins. However, it does produces lipids, cholesterol, and hormones.
It also assists in detoxification. which means it breaks down toxins. And the way it does so is by making these molecules more water-soluble so that they can be easily removed from the body or excreted through the urine.
Now let's go back to the rough ER. So once the rough ER, by means of the ribosomes, once they make the proteins, the proteins are enclosed in a vesicle and those vesicles get transported to the Golgi body, which is right there. Now, the Golgi body, it receives the vesicles, and it modifies the proteins that are in the vesicles.
And the way it does so is by adding lipids and carbs to the proteins, and it can also fold the protein. It can give it the proper shape, because the function of a protein is dependent on its shape. So once it modifies and processes the proteins, it exports the proteins out of the cell. So here is a visual illustration of what happens to a protein in a cell. Now granted, my drawing is not the best.
This is an educational video and not an artist or a how-to-draw video. And so the protein, it begins at the rough ER because that's where the ribosomes are. And remember, ribosomes, their job is to make proteins.
So the protein, it leaves the rough ER by means of a transport vesicle. And you can see the protein inside of this vesicle, and it goes to the Golgi body for processing and modification. So looking at the protein now, you can see that it has a different shape. At the same time, you can see different colors added to it.
So this represents the lipids and the carbs added to the protein. So once the protein has been tagged with those extra molecules, it gets exported out of the cell. So it travels to the cell membrane. where it leaves the cell to perform the function that it needs to do. Now the transport vesicle that surrounds the protein, it fuses with the cell membrane and so it becomes part of the cell membrane, causing the membrane to expand, or basically causing the cell to grow.
Now let's talk about some other organelles that you need to know. The next one is the mitochondria. Now the mitochondria has its own separate DNA.
It's different from the DNA of the cell. and its job is to perform cellular respiration. In that process, it takes the energy stored in fats and carbohydrates and converts it to a molecule known as ATP, adenosine triphosphate.
Next up, we have the lysosome. Now, the lysosome, which is here, its purpose is to break down food. It contains digestive enzymes, and in white blood cells, it can also destroy pathogens.
When a white blood cell engulf a pathogen in a process known as phagocytosis, the lysosomes in those white blood cells, it can break down those pathogens or disease-causing agents into smaller stuff that could be used or recycled by the cell. Next up, we have the cytoplasm. The cytoplasm is basically the jelly-like fluid that is in the cell.
So all of the organelles, they're dissolved in the cytoplasm. The cytoplasm contains solutes like salts, electrolytes, and other stuff like carbohydrates, lipids, and free-floating ribosomes, and things like that. Now let's talk about the cytoskeleton. The function of the cytoskeleton is to maintain the shape of the cell. At the same time, it also provides structural support.
Now the cytoskeleton... consist of a network of three fibers. The first of which is the microtubules, the second is the microfilaments, and the third one the intermediate filaments.
Now how can we identify them in the cell? The microtubules is the largest of the three fibers. The microfilaments is the smallest of the three fibers. The intermediate filaments, in terms of size, it's somewhere in between the microtubules and the microfilaments.
Now this picture really doesn't show it, but just know that the intermediate filaments there in between and they provide mechanical support to the cell. Now the microtubules, they're made up of a protein called tubulin and the microfilaments, they're made up of a protein called actin. The microtubules, their purpose is to provide structural support and transportation services to the cell. So vesicles, They can move from one part of the cell to another part by means of the microtubules.
The microfilaments, they're involved in elongation and contraction, so they assist the cell to move. Next up, we have the centrioles. And here it is in the diagram. The centrioles are active during cell division.
And during that time, they form something known as the mitotic spindle, which consists of... And what it does is during cell division it pulls apart the chromosomes thus allowing the cell to be split into two. The chromosomes are basically a condensed version of chromatin so they form during cell division. Now here are some other terms that you need to be familiar with. Cilia and flagella.
These also play a role in the movement of a cell. Now cilia consist of tiny short hair like structures and notice that there's many of them. Flagella consists of long whip-like structures and there's only a few of them and so the flagella can propel a cell forward from one location to another.
Now these two structures they're made up of microtubules. So microtubules they're very useful in the movement of a cell. So far we've been talking about animal cells. But now let's talk about the plant cell because even though they are similar, the plant cell has some characteristics that are not found in the animal cell.
The first of which is the presence of a very large vacuole. This vacuole stores water and nutrients and at the same time it provides structural support to the cell by means of the hydrostatic pressure that it generates. Now another organelle.
that's found in the plant cell but not in an animal cell is the chloroplast. Now the chloroplast is green due to a pigment known as chlorophyll, which plays a role in photosynthesis. Photosynthesis is a process by which the plant takes sunlight, carbon dioxide, and water, and it produces glucose and oxygen gas. Another feature that's present in plant cells, but not in animal cells, is the presence of a cell wall.
Now both the animal cell and the plant cell, they both contain a cell membrane. The cell membrane consists of a phospholipid bilayer, and it has a property known as selective permeability, which means that it allows some things to enter while preventing the passage of other things from coming into the cell. And it has these protein channels.
Now small molecules like oxygen gas and water they can diffuse right into the plasma membrane. But large molecules like glucose and other stuff, they have to go through a protein channel. Even ions have to travel through channels as well. And so that's the function of the cell membrane.
It's basically like the gate of the cell. It allows some things to enter while blocking the passage of other stuff from going into the cell. So that's basically it for this video.
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