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6.8.3. Microtubules


The microtubules are cylindrical formations, tube - shaped, hollow, about 25 nm in diameter, which wall is formed by the globular protein tubulin.

They can be found scattered in the cytoplasm or as part of the cilia, flagella and centrioles.

Structure and composition of microtubules

The microtubules, in a cross section, appear formed by thirteen protofilaments, leaving a central cavity. They are made up of two types of tubulinα-tubulins and β-tubulins, which associate to form dimers. In turn, these tubulin dimers associate to form each of the thirteen protofilaments that ultimately constitute a microtubule.

In animal cells, they grow from the centrosome.

Microtubule functions

Microtubules are scattered throughout the cytoplasm, fulfilling the following functions:

They collaborate in the maintenance of the cellular form.

Questions that have come out in University entrance exams (Selectividad, EBAU, EvAU)

Aragon. June 2004, option A, part A. Question 3 .- (2 points). September 2001, option B, question 4 .

Explain what they are:

c) microtubules (0.4 points)

Aragon September 2006, option B. Question 3

Answer the following questions:

a) Briefly explain a function carried out by the following molecules: microtubules (0.2 points)

Castilla La Mancha, June 2021, question 2.3

The three elements of the cytoskeleton are microfilaments (mostly actin), intermediate-sized filaments, and microtubules.

a. Define the latter (microtubules).
b. Name two organelles or cell structures formed from microtubules.
c. List TWO functions of the cytoskeleton.

Castilla La Mancha, July 2021, question 2.4

Colchicine (a drug extracted from plants of the genus Colchicum sp.), Is used as an anticancer and, in genetic studies, to make karyotypes. Its mechanism of action is simple: it binds to tubulin and prevents its polymerization, thus preventing the formation of the achromatic spindle and halting the mitosis process.

a. What is tubulin? Describe the structure of a microtubule.
b. What is the achromatic or mitotic spindle? At what point in mitosis does the spindle form?
c. What is a karyotype? What types of mutations can be detected with the karyotype?


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