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Besides bacteria and archaea, the cytoskeleton represents a complex, dynamic network of interlinking protein filaments that are most commonly found in the cytoplasm of all cells. It runs from the cell nucleus of the cell upto the cell membrane in all organisms and is made up of identical proteins. It is made up of three primary components in eukaryotes: microfilaments, intermediate filaments, and microtubules, all of which are capable of fast growth or disassembly depending on the cell’s needs. Microfilaments, microtubules, and intermediate filaments are the three types of cytoskeletal filaments found in eukaryotic cells. Neurofilaments are intermediate filaments found in neurons. Each kind is generally composed of a specific type of protein component and possess its own structure and intracellular distribution. Microfilaments are basically actin polymers having a diameter of 7 nanometers. Tubulin microtubules are 25 nm in diameter and made up of tubulin. Intermediate filaments are 8-12 nm in diameter and made up of varied proteins based on the type of cell in which they are found. The cytoskeleton gives the cell structure and shape, and it increases macromolecular crowding in this compartment by restricting macromolecules from portion of the cytoplasm.
Cytoskeletal Structure
However, all cells comprises a cytoskeleton, when the term “cytoskeleton” is used, it generally refers to the cytoskeleton of eukaryotic cells. Eukaryotic cells are multicellular organisms with nuclei and organelles. Eukaryotic cells are known to found in fungi, plants, mammals and protists. Prokaryotic cells are present in single-celled organisms such as bacteria and archaea and have no genuine nucleus or organelles save ribosomes. The cytoskeleton of prokaryotic cells was first identified in the early 1990s, after it was considered to be non-existent.
Microtubules are hollow rods that serve as “routes” for organelles to move along and help support and shape the cell. Microtubules are generally present in every eukaryotic cell. They are roughly 25 nm (nanometers) in diameter and vary in length.
Microfilaments, can also be referred as actin filaments these are basically tiny, solid rods that help muscles contract. Muscle cells generally possess a high concentration of microfilaments. They are found in all eukaryotic cells, just like microtubules. Microfilaments possess a diameter of about 8 nanometers and are generally composed of the contractile protein actin. They also help organelles move around.
Intermediate filaments are generally numerous in many cells and it helps to hold microfilaments and microtubules in place by providing support. Keratins in epithelial cells and neurofilaments in neurons are basically composed of these filaments. They mainly possess a diameter of 10 nanometers.
Function of Cytoskeleton
The cytoskeleton is found throughout the cytoplasm of the cell and controls a variety of functions.
It helps the cell in maintaining its original form and also provides support
The cytoskeleton helps in keeping a different variety of cellular organelles in place
It helps in the development of vacuoles
The cytoskeleton represents a dynamic framework that can deconstruct and reassemble its components to allow internal and overall cell motion. Transport of vesicles into and out of a cell, organelle migration, and chromosome manipulation during meiosis and mitosis all of these represents the examples of intracellular movements that are assisted by the cytoskeleton
Cell mobility is required for tissue formation and repair, cytokinesis (cytoplasm division) in the generation of daughter cells, and immune cell mainly responses to pathogens, all of which need the cytoskeleton
The cytoskeleton also functions the cells to communicate via transporting signals between them
In few types of cells, it is able to create a cellular appendage-like protrusions like cilia and flagella
Cytoskeleton Role in Motility
Cytoplasmic streaming is made possible by the cytoskeleton. This process, also known as cyclosis, includes the movement of the cytoplasm within a cell to circulate nutrients, organelles, and other substances. Endocytosis and exocytosis, or the transfer of substances into and out of a cell, are also aided by cyclosis. The contraction of cytoskeletal microfilaments aids in the direction of cytoplasmic particle flow. When the organelles are dragged along by microfilaments attached to them, the cytoplasm flows in the same direction.
Most eukaryotic and prokaryotic cells experience cytoplasmic streaming. In protists like amoebae, this process results in pseudopodia, which are cytoplasmic extensions. These structures are utilised to catch food and move about.
Conclusion
The cytoskeleton represents a framework that helps different cells to maintain their form and internal order while also providing mechanical support for cell division and mobility. A single cytoskeletal component does not exist. The cytoskeleton is made up of various different components that functions together to form it. Cell mobility is supported by cytoskeletal filaments. Microtubules slide along one other, for example, to move cilia and (eukaryotic) flagella. Cross slices of these tail-like cellular appendages reveal ordered microtubule arrays. The contractile capacity of actin filament networks is used to cause other cell motions, including the pinching off of the cell membrane in the end of the process of cell division (also known as cytokinesis). Actin filaments are incredibly active, forming and disassembling quickly. In reality, the crawling movement of cells like amoebae is based on this dynamic action. Actin filaments are actively polymerizing at the leading edge of a moving cell and rapidly depolymerizing at the rear edge. Actin assembly and disassembly are also aided by a large number of other proteins.
