mikrotubulukseen

Mikrotubulukseen are hollow, cylindrical structures found in the cytoplasm of eukaryotic cells. They are part of the cytoskeleton, a dynamic network that provides structural support, maintains cell shape, and plays a crucial role in intracellular transport and cell division. Mikrotubulukseen are composed of a polymer of tubulin, a globular protein that exists as alpha-tubulin and beta-tubulin heterodimers. These heterodimers assemble head-to-tail to form protofilaments, which then associate laterally to create the cylindrical structure of the mikrotubule. The assembly and disassembly of mikrotubulukseen are tightly regulated processes, allowing cells to rapidly reorganize their cytoskeleton in response to internal and external cues.

Mikrotubulukseen have a characteristic diameter of approximately 25 nanometers and a lumen of about 15 nanometers. They exhibit polarity, with a plus end where tubulin subunits are more readily added and a minus end where they are more readily removed. This polarity is essential for directed movement of motor proteins, such as kinesin and dynein, which transport vesicles, organelles, and chromosomes along mikrotubule tracks. In addition to their role in intracellular transport, mikrotubulukseen are the main structural components of cilia and flagella, which are involved in cell motility, and also form the spindle apparatus during mitosis and meiosis, ensuring accurate segregation of chromosomes. Microtubules also contribute to the maintenance of cell shape and provide tracks for the movement of other cytoskeletal elements.