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This cytoskeleton structure aids in the preservation of the shape and internal organization of cells, as well as the provision of mechanical support that allows cells to carry out essential functions such as division and movement. There is no single cytoskeletal component that contributes to its function. Rather, the cytoskeleton is composed of several different components that work together to form the structure.
What Constitutes the Cytoskeleton and How Does It Work?
eukaryotic cells have a cytoskeleton, which is composed of filamentous proteins, and it is responsible for providing mechanical support to the cell and its cytoplasmic constituents. There are three major classes of elements in the cytoskeleton, each of which has a different size and protein composition from the others. A protein called tubulin is responsible for the formation of microtubules, which are the largest type of filament with a diameter of about 25 nanometers (nm). Microtubules are composed of a protein called tubulin. Actin filaments are the smallest type of filament, with a diameter of only about 6 nm and made of a protein called actin. Actin filaments are found in the cytoplasm of all cells. Intermediate filaments, as their name implies, are in the middle of the size spectrum, with a diameter of approximately 10 nm. Intermediate filaments, in contrast to actin filaments and microtubules, are formed by the assembly of several different subunit protein complexes.
What Functions Do Microtubules Have?
The structure of microtubules, as well as how they polymerize and depolymerize, are depicted in a two-panel schematic diagram. The anatomy of a microtubule is discussed in detail in Panel A, which includes its components, size, and structure. In panel B, a series of schematic illustrations connected by arrows depict a microtubule growing during polymerization and shrinking during depolymerization, with the size of the microtubule increasing as the polymerization progresses. The shading in both panels indicates which tubulin dimers are bound to GTP and which are bound to GDP.
Tubulin is made up of two polypeptide subunits, and dimers of these subunits string together to form long strands known as protofilaments. Tubulin is a polypeptide that contains two polypeptide subunits. Microtubules are hollow, straw-shaped filaments that are formed by the joining of thirteen protofilaments in a single strand. Tubulin dimers at both ends of the filament are constantly being added and removed as a result of the constant addition and subtraction of tubulin dimers. In either case, the rates of change are not equal — one end grows more rapidly than the other and is referred to as the plus end, whereas the other end is referred to as the minus end. The minus ends of microtubules are anchored in microtubule organising centres, which are found in the cytoplasm of cells (MTOCs). It is the centrosome that serves as the cell’s primary MTOC, and it is usually found adjacent to the nucleus.
Microtubules tend to extend outward from the centrosome to the plasma membrane. During the non-dividing phase of the cell’s life, microtubule networks radiate out from the centrosome to provide the cytoplasm with the fundamental organization necessary for cell function, including the positioning of organelles.
What Are the Functions of Actin Filaments?
Photographs and a schematic diagram of the cytoskeletal elements of a neuron are provided for your viewing pleasure. The diagram shows the neuron’s cell body, axon, and growth cone, all of which are labelled. A magnified diagram of each of these cytoskeletal elements is shown for each of the highlighted cytoskeletal elements (microtubules, intermediate filaments, and actin filaments). An image of an axon and a growth cone on a black background is depicted in the photomicrograph, with microtubules in green and actin filaments in red indicating the presence of fluorescent proteins.
All eukaryotic cells contain large amounts of the protein actin. In skeletal muscle, where actin filaments slide along the filaments of another protein called myosin to cause the cells to contract, actin was discovered for the first time. (Actin filaments are less organised in nonmuscle cells, and myosin is much less prominent in these cells.) Actin filaments are composed of identical actin proteins that are arranged in a long spiral chain to form a filament. Actin filaments, like microtubules, have plus and minus ends, with more ATP-powered growth occurring at a filament’s plus end than at its minus end.
Many types of cells have actin filament networks beneath the cell cortex, which is a network of membrane-associated proteins that supports and strengthens the plasma membrane. Actin filament networks are found beneath the cell cortex in many types of cells. Cells can hold — and move — specialized shapes, such as the brush border of microvilli, because of the existence of such networks. Actin filaments are also important in the processes of cytokinesis and cell migration
The actin filaments that support the cell structures are depicted in a four-part schematic diagram. Microvilli, cytoplasmic contractile bundles, lamellipodia, filopodia, and the cell division contractile ring are some of the structures depicted in this illustration. Using illustrations of blue cells with circular, purple nuclei and white actin filaments, the structures can be better understood.
What Are the Functions of Intermediate Filaments?
Intermediate filaments are available in a variety of forms, but they are generally strong and ropelike in appearance. Intermediate filaments are primarily mechanical, and as a group, they are less dynamic than actin filaments or microtubules in terms of their function. Microtubules and intermediate filaments are frequently found working in conjunction with one another, providing strength and support for the fragile tubulin structures.
Intermediate filaments are present in all cells, but the protein subunits that make up these structures differ. Intermediary filaments are found in a variety of cell types, with some intermediate filaments being associated with specific cell types in particular. Neurofilaments, for example, are found only in neurons (most prominently in the long axons of these cells), desmin filaments are found only in muscle cells, and keratins are only found in epithelial cells, among other cell types. Other intermediate filaments are found in a more widespread distribution. Vimentin filaments, for example, can be found in a wide variety of cell types and are frequently found near microtubules. The lamins, on the other hand, are found in all cell types and form a meshwork on the inside of the nuclear membrane, which serves to reinforce it. It is important to note that intermediate filaments are not polar in the same way that actin and tubulin are.
The composition of an intermediate filament is depicted in a three-part schematic diagram. A single filament is depicted in the lower right corner. It has a long cylindrical shape and appears to be a strand of liquorice made up of thinner rod-like structures, much like a strand of candy. The arrangement of the rods into a sheet-like structure can be seen clearly in a magnified version of the illustration. Two rods are shown in greater detail in a more detailed representation of this arrangement. Each appears to be made up of two thinner filaments that have been coiled around one another in a circle. A label on one end of each rod denotes the amino terminus (NH2), and a label on the other end denotes the carboxyl terminus (CH2) (COOH). Specifically, two rods are arranged antiparallel to one another, with one rod having an amino terminus at the left and one having a carboxyl-terminus at the right, and the other rod having an amino terminus at the right and one having a carboxyl-terminus at the left.
Conclusion
Eukaryotic cells have a cytoskeleton, which is composed of filamentous proteins, and it is responsible for providing mechanical support to the cell and its cytoplasmic constituents. There are three major classes of elements in the cytoskeleton, each of which has a different size and protein composition from the others. A protein called tubulin is responsible for the formation of microtubules, which are the largest type of filament with a diameter of about 25 nanometers (nm). Microtubules are composed of a protein called tubulin. Microtubules, actin filaments, and intermediate filaments are the structural components of the cytoskeleton of a cell. These structures give the cell its shape and assist in the organisation of the cell’s constituent parts. Aside from that, they serve as a foundation for cell movement and division.
