Centrioles its structure and functions – Biology Notes for Class 11
Biology Notes for Class 11 – In this article, we will discuss Centrioles its structure and functions out for Class 11 Biology.
Centrioles are cylindrical, rod-shaped, microtubular structures. They occur in a pair near the nucleus. The pair of centrioles is often called diplosome. The two centrioles are usually at right angles when they are close to each other. A pair of centrioles is contained within a structure called centrosome, present near the nucleus. The structure of a centriole is an array of nine groups of microtubules equally spaced around the perimeter of an imaginary cylinder. The space between and immediately around the triplet is filled with an amorphous, electron-dense material. The centrioles lack limiting membrane and DNA or RNA. The centrioles are found in pairs but move towards the poles (opposite ends) of the nucleus during cell division.
Centrosome (with a pair of centrioles)
Centrioles are approximately 0.3-0.5 µm in length and 0.15µm in diameter. They are found in most algal cells, except red algae, moss cells, some fern cells and most animal cells. They are absent in prokaryotes, yeast, cone-bearing and flowering plants. They are also not present in non- flagellated or non- ciliated protozoans such as amoebae.
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Structure of a Centriole
A centriole is made of nine sets of microtubules, each in groups of three known as triplet microtubules. The arrangement is known as 9+0, unlike cilia and flagella that contains doublet microtubules in a 9+2 arrangement. Triplet microtubules are very strong because they are composed of three concentric rings of microtubules that form together. Triplet microtubules are seen in other strong microtubules structures, such as the basal bodies of cilia and flagella. Each triplet is bonded together by special proteins that give a centriole its shape. Surrounding the triplet microtubules is an amorphous material called pericentriolar material, which contains many of the molecules necessary for the construction of microtubules. Each microtubule in a triplet is made up of small units of tubulin, a small monomer that can join together to create long, hollow tubes that resemble straws.
Centrioles arranged at right angles
Function of a Centriole
Centrioles are a very important part of centrosomes. Centrosomes are involved in organizing microtubules in the cytoplasm. The position of the centriole determines the position of the nucleus and plays a significant role in the spatial arrangement of the cell. Microtubules play a major role in cell division, motility, intracellular transport, and are also important to maintain the structural integrity of a cell.
Microtubules play an important role as tracks in the intracellular transport of membrane-bound vesicles and organelles, and this process is supported by motor proteins such as dynein. Microtubules are cytoskeletal fibres that have an important role in the mitotic spindle during mitosis.
Centrioles are the nucleation points for spindle formation during mitosis and meiosis (cell division), they are also the basal body for cilia and flagella.
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Tag: Centrioles, Structure of a Centriole, Function of a Centriole, Biology notes for Class 11