Microtubules

Microtubules are microscopic, hollow tubes made from alpha and beta-tubulin that are a neighborhood of the cell’s cytoskeleton. Microtubules extend throughout the cell providing it with proper shape and keeping the organelles their original place. They are the most important structures within the cytoskeleton and are about 24nm thick. They facilitate cell movement, cellular division, and transportation of materials within the cells. They are also involved in the division of chromosomes during the process of mitosis and in locomotion.

Microtubules Structure

Microtubules are arranged within the sort of microtubule-organizing centers. They are structures found in eukaryotic cells. During the interphase, most of the animal cells consist of microtubule-organizing centers. Several proteins are sure to microtubules namely dynein and kinesin.

Microtubules are made of subunits called tubulin. Each tubulin is made of an alpha and a beta-tubulin attached to each other. This tubulin is a heterodimer. Microtubules play an important role altogether in eukaryotic cells. These cells release protein tubulin during a normal manner that involves transcription of the gene coding for tubulin that yields RNA and is followed by transcription of mRNA to supply proteins. The inner space of the hollow cylinder of microtubules is termed as Lumen.  

Microtubule Function

Following are the important functions of Microtubules:

• Cell Movement

Microtubules give structures to cilia and flagella. They also facilitate the contraction and expansion of the cell helping them to move from one place to another.

• Cell Division

Microtubules play a serious role in forming the mitotic spindles. These mitotic spindles organize and separate the chromosomes during cell division.

• Cell Transport

Microtubules help in the movement of organelles inside the cytoplasm of the cells. They also help various areas of the cell to communicate with each other.

Role of Actin Filaments

The protein actin is abundant in all eukaryotic cells. It was first discovered in striated muscle, where actin filaments slide along filaments of another protein called myosin to form the cells contract. (Actin filaments are less organized and myosin is far less prominent with the nonmuscle cells,) Actin filaments are made from identical actin proteins arranged during a long spiral chain. For instance, like the microtubules, actin filaments have plus and minus ends, with more ATP-powered growth occurring at a filament's plus end.

In many sorts of cells, networks of actin filaments are found beneath the cell cortex, which is that the meshwork of membrane-associated proteins that supports and strengthens the cell wall. Such networks allow cells to carry and move specialized shapes, like the comb border of microvilli. Actin filaments also are involved in cytokinesis and cell movement.

Intracellular Organization of Microtubules

In the cytoplasm, microtubules form a structural network. The functions of the cytoskeleton in microtubules include chromosomes segregation, transport, mobility, and mechanical support. It can either shrink or grow to get energy which is because of the presence of motor proteins that allow cellular components et al. to be carried alongside microtubules.

The arrangements in microtubules are limited to a cell -type. So that it would be easy to facilitate the transportation of organelles, vesicles, and proteins along the apical-basal axis of the cell. They play a vital role in cell migration as well.