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The left part of this figure is a molecular model of 13 polymerized dimers of alpha- and beta-tubulin joined together to form a hollow tube. The right part of this image shows the tubulin structure as a ring of spheres connected together.
Microtubules are hollow. Their walls consist of 13 polymerized dimers of α-tubulin and β-tubulin (right image). The left image shows the tube’s molecular structure.

Source: OpenStax Biology 2e

OpenStax Biology 2e

As their name implies, microtubules are small hollow tubes. Polymerized dimers of α-tubulin and β-tubulin, two globular proteins, comprise the microtubule’s walls. With a diameter of about 25 nm, microtubules are cytoskeletons’ widest components. They help the cell resist compression, provide a track along which vesicles move through the cell, and pull replicated chromosomes to opposite ends of a dividing cell. Like microfilaments, microtubules can disassemble and reform quickly.

Microtubules are also the structural elements of flagella, cilia, and centrioles (the latter are the centrosome’s two perpendicular bodies). In animal cells, the centrosome is the microtubule-organizing center. In eukaryotic cells, flagella and cilia are quite different structurally from their counterparts in prokaryotes.

– What are protein filaments in the cytoplasm of eukaryotic cells that form part of the cytoskeleton?

– What are cytoskeletal structural components found in the cells of vertebrates and many invertebrates?

Microtubules are dynamic polymers essential in the proper development and maintenance of a healthy nervous system. Previously, increasing evidence linked the defective regulation of microtubules to a spectrum of disorders from neurodevelopmental to neurodegenerative diseases. Acetylation of tubulin determines the biochemical and biophysical diversity of microtubules, regulates their function, and has been recently related to the molecular events underlying different disorders including schizophrenia, autism, and Alzheimer’s disease.


Clark, M., Douglas, M., Choi, J. Biology 2e. Houston, Texas: OpenStax. Access for free at: https://openstax.org/details/books/biology-2e