Centrosome and Centrioles
Definition of Centrosome - Centrosomeis a more or less spherical mass of dense cytoplasm situated close to the nucleus and contains a pair of cylindrical bodies which are concerned with spindle formation during cell division. In 1888 Boveri first discovered these organelles and gave its name.
Distribution of the Centrosome – Centrosome is observed in almost all the animal cells, as it is associated with the spindle formation of the cell during cell division. But in plant cells centrosome is totally absent except some lower plants like algae. Thus during cell division spindle is not formed during cell division of plant cell.
Chemical Composition of Centrosome - Chemically these are made up of protein, carbohydrate, lipid, nucleic acid (RNA and probably DNA).
Structure of Centrosome - Kinoplasm is the organising material of centrosome. It can be divided into two part. These are – Centrioles and centrosphere. At the middle portion of the centrosome contains two hollow cylindrical structure called Centrioles which lying their long axis . These two Centrioles of the centrosome are called diplosome.
The wall of Centrioles are made of 9 longitudinally arranged bundles of microtubules. Each of them is connected to the adjacent one by a central rod by means of protein fibres.It seems like a cart wheel. Microtubules bundles are radially equidistant from the adjacent ones . Each single bundle is composed of set of three microtubules called triplet microtubules. They are parallel to each other and are arranged tangentially to the circumference of the centrioles. Each of them has a diameter of 250 angstroms and wall is made up of 13 fillaments of globular proteins with a diameter of 45 angstroms. Some of the spheroidal bodies known as centriolar satellites encircle the whole centrioles in two circumferential rows.
Definition of Centrioles - Centrioles are pair of cylindrical shape hollow organelles which is associated with spindle formation during cell division and is a part of centrosome.
Origins of Centrioles - The process of formation of Centrioles are still unknown centrioless are originated from the pre existing one by the process called replication.It is observed that, during the this, a procentriole is formed behind the mother Centrioles and each of them remain at right angle to its respective mother Centrioles. Procentrioles are look like mother Centrioles but are shorter in length. Then the microtubules increase in length and converted to mature Centrioles.Procentrioles are lied very close to the mother Centrioles but in a definite arrangement. Though they don’t have any connections between them and it seems clear that unequivocally a new Centrioles originates by the division of a pre existing Centrioles.
Functions of the Centrosome:
Functions of Centrosome are –
1. Formation of Centrioles - Centrioles are formed from the Centrosome during cell division.
2. Plays role in cell Division - At the time of cell division ,the centrioles form spindle fibres that help in migration of daughter chromosome towards the pole.
3. Movement of Locomotion - Centrioles help in the formation of cilia,flagella,tail of sperms. These are made up of microtubules and function as organs of movement and locomotion of certain cells.
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