Microtubules

In cytoplasm of cages, except membrane structures and organellas, a large number various the fibrillyarnykh of the educations which are carrying out various functions meets.

Microtubules (microtubuli) of the proteinaceous nature belong to such fibrillyarny components. In cytoplasm they can form temporary difficult educations, for example a spindle of cellular division. Microtubules are a part of elaborate special organellas, such as tsentriol and bazalny little bodies, and also are the basic structural elements of eyelashes and zhgutik.

Microtubules represent straight lines, not branching long hollow cylinders. Their external diameter makes about 24 nanometers, the internal gleam has width of 15 nanometers, and wall thickness — 5 nanometers. The wall of microtubules is constructed at the expense of densely laid roundish subjedinitsa (of protein of a tubulin) about 5 nanometers. In an electronic microscope on cross sections of microtubules are visible the most part of 13 subjedinitsa built in the form of a single-layer ring. The microtubules allocated from different sources (an eyelash of protozoa, cells of nervous fabric, a division spindle), have similar structure and contain proteins — tubulina.

Believe that in a cage of a tubulina exist in two forms — free and connected. Shift of balance between these forms can lead or to dissociation (disintegration) of microtubules, or to their growth. Neither tubulina in pure form, nor the microtubules constructed of them aren't capable to reduction, they don't possess ATF-aznoy activity. Most likely they carry out a role of rigid frame structures. In cages of a microtubule take part in creation of a row temporary (a cytoskeleton the interfaznykh of cages, a division spindle) or constant structures (a tsentriola, an eyelash, a zhgutika).

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