Explain the structure of microtubules. What functions do they perform?

In morphological terms, microtubules are long hollow cylinders with an external diameter of 25 nm. The microtubule wall consists of polymerized tubulin protein molecules. During polymerization, tubulin molecules form 13 longitudinal protofilaments, which are twisted into a hollow tube. The change in tubulin monomer is about 5 nm, equal to the thickness of the microtubule wall, in the cross section of which 13 globular molecules are visible. Functions:
1. Maintaining the shape and polarity of the cell, the distribution of its components.
2. Providing intracellular transport.
3. The provision of movements of the cilia, chromosomes in mitosis,
4. The formation of the basis of other organelles (centrioles, cilia).

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