The cytoskeleton is composed of three main types of protein filaments: microfilaments , intermediate filaments , and microtubules. These structures provide mechanical support, maintain cell shape, enable intracellular transport, and facilitate cell movement and division.
Components of the Cytoskeleton
Microfilaments (Actin Filaments)
Microfilaments are the thinnest filaments, primarily made of actin proteins arranged in a double helix. They are concentrated near the plasma membrane and form a network called the cell cortex, which helps maintain cell shape and resist deformation. Microfilaments interact with myosin and ATP to enable cell motility, muscle contraction, and cytokinesis during cell division.
Intermediate Filaments
Intermediate filaments are more rigid and stable than other cytoskeletal components, providing tensile strength and mechanical stability to cells. They are composed of various proteins depending on cell type—for example, keratin in epithelial cells and desmin in muscle cells. These filaments anchor organelles like the nucleus in place and help cells withstand mechanical stress.
Microtubules
Microtubules are hollow tubes made of tubulin protein subunits (alpha and beta tubulin) and are the thickest of the three filament types. They radiate from the centrosome and serve as tracks for motor proteins like kinesin and dynein, which transport vesicles and organelles using ATP. Microtubules are essential for chromosome segregation during mitosis and form the structural basis of cilia and flagella, enabling cell motility [web: