In this centrioles structure and its function post we have briefly explained about centrioles, definition, components, chemical composition, functions and importance.
Centrioles Structure and Its Function
Van Benden in 1880 discovered centrosome in cells of certain parasites of cephalopods. Centrosome is the area of cytoplasm, often a clear zone, around the centriole. It is found lying in the center of the cell, near the nucleus, in the cytoplasm.
In Metazoa, centrosome lies outside the nucleus, but in Protozoa it lies within the nucleus. It is lacking in some plant cells. T. Boveri in 1888 described centrosome in detail. The substance of centrosome also called kinoplasm consists of two parts: (i) Smaller bodies or centrioles, (ii) Surrounding mass or centrosphere.
Centrioles are cylindrical (tube-like) structures/organelles composed of microtubules that are found in eukaryotic cells. Centrioles in the cell aid in cell division by facilitating chromosome separation. As a result, they are close to the nucleus. Apart from cell division, centrioles play a role in the formation of cilia and flagella, which aids in cell movement.
All centrioles are made up of 9 groups of microtubule triplets arranged in a cylinder shape. Only an electron microscope can reveal the intricate structure of centrioles. These are connected at right angles to each other.
Drosophila melanogaster and C. elegans embryos are exceptions to this rule. The former forms 9 pairs of microtubules instead of triplets, whereas C. elegans premature embryos and sperm cells have 9 single microtubules.
In 1883 and 1888, Edouard van Beneden and Theodor Boveri observed and identified the centrioles for the first time. In the 1950s, Joseph G. Gall and Etienne de Harven proposed the structure of centriole duplication.
The centriole aids in the organisation of the mitotic spindle and the completion of the cytokinesis process. Centrioles, on the other hand, were thought to be required for the formation of the mitotic spindle in the animal cell.
Several recent types of research have explained that a cell that lacks a centriole (which has been surgically removed using a laser) can function without it in the G1 level of interphase and can be formed later in a de novo manner.
The position of the centrioles is important in the three-dimensional organisation of the cell because it regulates the position of the nucleus. The location of such an organelle in flagellated and ciliated organisms is determined by the mother centrioles that form the base.
The microtubule of the centriole is composed of a protein tubulin and some lipids having a high concentration of ATPase enzymes. They seem to contain RNA and a small DNA molecule. Proteins encoded by this DNA are presumably translated on cytosolic ribosomes and then incorporated into the centriole.
Functions of Centriole
1. The centrioles are involved in the formation of the spindle apparatus that plays a major function during cell division.
2. Centrioles are located in the cell nucleus as it helps in cell division by facilitating the separation of chromosomes.
3. However, when the centriole is absent there is a divisional error and delay in mitotic processes.
4. Aside from cell division, they assist in the movement of the cell as they are involved in ciliogenesis which is the formation of cilia and flagella on the surface of the cell. Basal bodies direct cilia and flagella.
5. The centrioles also function to form the sperm flagellum and aid sperm movement. The Sperm centriole aids in the development of the embryo after fertilization. The sperm supplies the centriole that forms the centrosome and microtubule system of the zygote.
6. During mammalian development, the proper orientation of cilia through centriole positioning toward the posterior of embryonic node cells is crucial to establish left-right asymmetry.
7. The position of the centriole also determines the position of the nucleus. Centriole also plays an important role in the spatial arrangement of the cell.
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