Hi. In this video, we're going to be talking about an overview of the cytoskeleton. So what is the cytoskeleton? Well, the cytoskeleton is kind of like a country's roadways. Right? So in a country, people need to travel around to different cities, or they need to transport goods, and that's exactly what the cytoskeleton does for the cell. And so the cytoskeleton is this intricate network of roadways essentially that go throughout the entire cytoskeleton, but instead of being made of concrete, these roadways are made up of different types of protein filaments. And these protein filaments are very organized, just like our roads. I mean, we can look at a map, and we can get anywhere we want to, just by using our road systems. The same thing is in the cell. It's very organized. But unlike the roadways, the cytoskeleton is dynamic, and so what this means is that it is constantly moving and responding to the environment. So our roadways, whenever we make a road or a highway, that pretty much stays there. Right? Like, sometimes they tear down a road or two, but it's not that every single day that road is moving and changing places. The cytoskeleton is much more like sort of those moving staircases in Harry Potter. They're constantly moving, readjusting their direction. They can be taken apart, put back together in just a matter of seconds. And so, they're constantly moving and constantly responding to their environment. So, they're very organized, but their organization is constantly moving. I guess that's much more like the Harry Potter stairways. And so, there are 3 main components of the cytoskeleton. We have these are called, intermediate filaments, microtubules, and actin filaments. Sometimes actin filaments are called microfilaments. But essentially, let's start with intermediate filaments here. And the purpose of this is to provide tensile strength to the nucleus. So, this kind of acts like a protective cage around the DNA because it's around the cell and the nucleus. So it kind of protects the nucleus, and it provides tensile strength, meaning that if something gets pressed together, that tensile strength is going to hold its shape. It's going to just kind of protect that DNA in the roadways. This is or those staircases, depending on which analogy you like. Microtubules are the roadways of the cell. They provide this internal framework, so they kind of provide these like bridges and things throughout the cell. They keep the cell shape, they allow things to be transported across from them. They also play a major role in mitosis, so in cell division. They are responsible for moving that DNA around, helping the cell, move its shape around, depending on what's going on in mitosis at the time. And then they also perform or they make up different unique structures called cilia and flagella, which we're going to talk about a lot in its own topic. But, cilia and flagella are pretty much they allow for cell movement or the cell to move things outside of the environment. And so these microtubules, these are super, super, super important because they're not only acting as roadways, they provide support, they really assist in cell division, and they create distinct organelles that are really important for cell movement for certain types of cells. And then we have actin filaments, which are also called microfilaments. Either thing is the exact same thing, whether you call it actin or microfilament, but these really line the plasma membrane and they help the cell maintain its shape. And so if the cell shape needs to change, for instance, if a cell is moving throughout the body, that cell shape needs to change a lot, then the actin filaments are in charge of that. So here's a microscope slide of the cytoskeleton being labeled. So we can see actin is in red and you can see that's really close to the external part of the cell because it's lining that plasma membrane. And here we have microtubules which are labeled in green, and you can see those are this really intense network that's traveling throughout the entire cell. It's acting as it's providing a roadway essentially for the entire cell. And you can see it goes everywhere, all the way out to the plasma membrane around the nucleus. It can be really highly isolated in some regions, but essentially it travels throughout the whole cell. So how are these cytoskeleton components created? So even though there are 3 different filaments, and we're going to talk about each one of those individually and what the differences are, the actual formation of those filaments and some of their structures are very similar, even though if some of the intricate details are different. So all of these filaments are created, so the actin filaments, the intermediate filaments, and the microtubules are created, through the joining of small subunits. And we call these subunits monomers, and we'll go through each monomer for each different filament is called something different, and we'll talk about that later. But essentially these monomers are joined together through non-covalent bonds. So remember, we want these non-covalent bonds because we said that the cytoskeleton is dynamic, so it's constantly being created and broken down. So the only way that can happen is if we do weaker bonds, which are those non-covalent bonds. And so there are a couple of structures that you need to know. The first is going to be protofilament, and this is what happens when these monomers are joined together. So we have this monomer here, and we join it to this one here, and we join it to this one here, and eventually, you're going to get these long things we call protofilaments. So it's the long string of subunits that we've joined end to end, just like here. So we have this end connecting to this end, connecting to this end, and so on and so forth, and these things can be hundreds of thousands of monomers long. And then when we have multiple protofilaments, often what happens in these, and we'll talk about each individual case individually, but often what happens if we get multiple protofilaments, they end up twisting around each other kind of like a rope, where they form like this helical lattice, which kind of just like if you had two strings and you twisted them, then that's kind of what that would end up looking like. And that's very common in the cytoskeletal components. And then the last term that you really need to know, and this one's super, super important, and that is called nucleation. And essentially, this is how these things get started. So remember, we're starting with these one, these just individual monomers, but eventually, two monomers have to come together. And this process here of the first two monomers coming together actually is really difficult. It's not that easy. Once two monomers are together, it's super easy to add more on. But just like getting those first two together is really difficult, and so this process here is called nucleation. It's the initiation process. So the first time these subunits are assembled together, and it's a special process that isn't actually that easy. So here's an example of nucleation of actin. So we have these actin monomers, they're right now they're called G actin and we'll explain that term later. But, these are actin monomers, it requires some type of energy, like I said it's not easy to go through nucleation, you're going to have some kind of energy, in this case, it's ATP. So ATP gets added to all of these G actins, and then it forms, the nucleation step, forms the first couple of monomers together, and then once these monomers have formed, then the rest of it can be formed super easy. They just start attaching on really easy once the first few have gotten together. So, that is just the overview of the cytoskeleton, the components, the intermediate filaments, microtubules, and actin. We'll go over each one individually, and then just some introductory terms on how these filaments are formed in the cell. So with that, let's move on.
Overview of the Cytoskeleton: Videos & Practice Problems
The cytoskeleton is a dynamic network of protein filaments that provides structure and organization within the cell, akin to roadways in a country. It consists of three main components: intermediate filaments, microtubules, and actin filaments (microfilaments). Intermediate filaments offer tensile strength, microtubules serve as transport pathways and are crucial for mitosis, while actin filaments help maintain cell shape and facilitate movement. These filaments are formed through the assembly of monomers via non-covalent bonds, with nucleation being the initial challenging step in their formation.
Cytoskeleton Overview
Video transcript
Which of the following is not a component of the cytoskeleton?
What is the name of the initiation process that beings to assemble the subunits of the cytoskeleton?
Here’s what students ask on this topic:
What is the cytoskeleton and what are its main components?
The cytoskeleton is a dynamic network of protein filaments that provides structure, organization, and movement within the cell. It is akin to a country's roadways, facilitating the transport of materials and maintaining cell shape. The cytoskeleton consists of three main components: intermediate filaments, microtubules, and actin filaments (also known as microfilaments). Intermediate filaments provide tensile strength and protect the nucleus. Microtubules act as transport pathways, support cell shape, and play a crucial role in mitosis. Actin filaments help maintain cell shape and facilitate cell movement. These components are formed through the assembly of monomers via non-covalent bonds, with nucleation being the initial challenging step in their formation.
Created using AIHow do microtubules contribute to cell division?
Microtubules play a crucial role in cell division, particularly during mitosis. They form the mitotic spindle, a structure that segregates chromosomes into the daughter cells. During mitosis, microtubules attach to the chromosomes at their centromeres via kinetochores. They then help align the chromosomes at the metaphase plate and pull them apart during anaphase, ensuring that each daughter cell receives an identical set of chromosomes. Additionally, microtubules help in the reorganization of the cell's internal structure, facilitating the division process.
Created using AIWhat is the process of nucleation in the formation of cytoskeletal filaments?
Nucleation is the initial and challenging step in the formation of cytoskeletal filaments. It involves the assembly of the first few monomers to form a stable nucleus, which then allows for the rapid addition of more monomers. For example, in the formation of actin filaments, actin monomers (G-actin) require ATP to initiate nucleation. Once the first few monomers are assembled, the rest of the filament can grow quickly as additional monomers attach easily. This process is essential for the dynamic nature of the cytoskeleton, allowing it to constantly reorganize in response to cellular needs.
Created using AIWhat are the functions of actin filaments in the cell?
Actin filaments, also known as microfilaments, have several critical functions in the cell. They primarily line the plasma membrane, helping to maintain and change the cell's shape. This is particularly important for cell movement, such as during cell migration or division. Actin filaments also play a role in muscle contraction, where they interact with myosin to generate force. Additionally, they are involved in various cellular processes, including endocytosis, cytokinesis, and the maintenance of cell junctions. Their dynamic nature allows them to rapidly assemble and disassemble in response to cellular signals.
Created using AIHow are intermediate filaments different from microtubules and actin filaments?
Intermediate filaments differ from microtubules and actin filaments in several ways. Structurally, they are composed of different protein subunits and provide tensile strength rather than dynamic movement. Intermediate filaments form a protective cage around the nucleus and help maintain the cell's mechanical integrity. Unlike the highly dynamic microtubules and actin filaments, intermediate filaments are more stable and less frequently reorganized. Microtubules, made of tubulin, act as transport pathways and are crucial for mitosis, while actin filaments, composed of actin, are involved in maintaining cell shape and facilitating movement.
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