The cytoskeleton is an active structure that integrates eukaryotic cells, which allow the cell shape to be maintained or modified, responding to internal or external stimuli. The activities of the cytoskeleton are very varied, most of them depend on the cell type, some of them are: Maintenance of cell structure and shape. Allows for movement and allows cell division.
The cytoskeleton is made up of three types of protein filaments that are very different in their composition, function and characteristics:
Actin filaments or microfilaments: they are those that form a network close to the plasma membrane. They are characterized by being very flexible, their thickness is 5 to 9 nanometers. They originate from the polymerization of the actin particle. These filaments are present in animal cells and in plant cells. They are very important in the process of cell movement and cohesion. In the same way, they intervene significantly in cell division. Another important function of actin filaments originates in muscle tissue, where they are associated with motor proteins called " myosins " which cause muscle contraction.
Microtubules: are those that originate from the polymerization of a dimer comprised of alpha and beta tubulin. This type of filament is characterized by being rigid and hollow, its thickness is 25 nanometers. They are responsible for the movement of cilia and flagella, in addition to the movements of intracellular vesicles. They are generated in the microtubule-producing centers, hosting a radial organization in the interphase cells. They are highly dynamic structures, supported by a set of proteins called microtubule-associated proteins.
Intermediate filaments: unlike the first two that are made up of globular proteins, the intermediate filaments are made up of polymerized filamentous proteins. Its thickness is 8 to 10 nanometers, which reflects an intermediate between actin filaments and micrutubules. Its main function is to serve as a structural support for the cell, since thanks to its strength it protects cells against stresses and pressures.
The intermediate filaments are of different types: nuclear lamina filaments (they are those that ensure the nuclear membrane), keratin (protect epithelial cells), neurofilaments (located in nerve cells)