mikrotubulusfilamentit

Mikrotubulusfilamentit, often simply called microtubules, are microscopic, hollow tubes composed of protein subunits called tubulin. They are a fundamental component of the cytoskeleton in eukaryotic cells, playing critical roles in maintaining cell shape, facilitating intracellular transport, and enabling cell division. Microtubules are dynamic structures, constantly assembling and disassembling in a process known as dynamic instability. This dynamic nature is essential for their various functions.

The primary protein subunit of microtubules is tubulin, which exists as alpha-tubulin and beta-tubulin heterodimers. These dimers assemble into protofilaments, which then arrange themselves in a cylindrical fashion to form the microtubule wall. The arrangement of these protofilaments creates the characteristic hollow lumen of the microtubule.

Microtubules are organized by structures called microtubule-organizing centers (MTOCs), the most prominent being the centrosome. MTOCs nucleate microtubule growth, dictating their polarity and spatial distribution within the cell. Motor proteins, such as kinesins and dyneins, bind to microtubules and use them as tracks to move cargo, including organelles and vesicles, throughout the cytoplasm.

During cell division, microtubules form the mitotic spindle, which is responsible for separating chromosomes into the daughter cells. They also form cilia and flagella, which are involved in cell motility and fluid movement. The disruption of microtubule function can have severe consequences for cell viability and is often a target of therapeutic agents, such as some chemotherapy drugs.