Question

Microtubules are made up of?
(a) Actin
(b) Tubulin
(c) Fibrin
(d) Nexin

Answer 1

Microtubule is highly dynamic polymers that are part of the cytoskeleton which provides structure and shape to the eukaryotic cells. They are composed of specialized globular protein that helps in giving structure to the living cell.

Complete answer
Microtubules are long fibers of indefinite length found in the cytoplasm of the cell. The structure of the microtubule constitutes a hollow center with a dense wall. The wall is composed of 13 protofilaments that are again composed of tubulin protein. Thus the microtubules are made up of two types of tubulin proteins found in a dimeric form are the alpha and beta-tubulin proteins. The structure of microtubules includes the arrangement of protofilament at the long axis in a parallel manner while the arrangement of the alpha and the beta-tubulin proteins is alternate along the length. Some other proteins are also linked with the Microtubules that include dynein and kinesin.

So the correct answer is option (b), Tubulin.

Additional information:
The functions of microtubules are as follows:
- Microtubules help in the formation of cilia and flagella that help in the movement and locomotion of the cell.
- Special arrangement of microtubules that include centrioles and basal bodies will give rise to the formation of cell organelles.
- They are responsible for the chromosomal arrangement in the cells along with their separation and organization during the process of cell division resulting in the formation of the mitotic spindles.
- The important functions of microtubules are transportation and communication among various cell organelles that include mitochondria, where the movement of chromosomes, vesicles, and granules takes place.

Note:
The tubulin is also known as the heterodimer as it is made up of two different subunits forming a dimer. They help in the formation of the cytoskeleton along with other components like microfilaments and intermediate filaments. During cell division, the centrioles that develop from the cilia and flagella will form the spindle fibers.