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A centrosome is an organelle that usually consists of two cylindrical structures. These structures are known as centrioles. Both the centrioles in a centrosome lie perpendicular to each other and form an arrangement like a cartwheel concerning each other. An indeterminate pericentriolar material surrounds centrioles in the centrosome. The two centrioles found on the centrosome are referred to as a daughter centriole and a mother centriole. Both the centrioles are linked together by interconnecting fibers, which usually consist of a complex protein. Such complex proteins help in the synthesis of more microtubules.
The term Centrosome means central body, which Theodore Boveri coined in 1888. He defined the Centrosome as an organelle that occupies a central position in the interphase cells. A centrosome is not found in fungi and plant cells. Therefore, they use other structures for the proper organization or arrangement of microtubules. It is the property of this organelle that the spindle fibers radiate as an aster in mitosis in the animal cells. It is the major microtubule-organizing center in the eukaryotic cells.
Structure of the Centrosome
The centrosome consists of two centrioles surrounded by an amorphous amount of Pericentriolar material (PCM). It is also described as a centrosphere. Each centriole looks like a cylinder about 300-500 nm in length while 150-200 nm in diameter. The wall of each centriole contains nine triplet fibers arranged around a central axis. These triplet fibers consist of three secondary fibers or known as tubules.
Within the region of PCM, a highly insoluble structure called centromatrix is found. This region functions as a frame for the binding of ring-shaped protein complexes. These complexes are made up of ℽ-tubulin proteins. It includes other proteins like centrin, pericentrin, ninein, and centrosomin.
Centrosome ability to nucleate microtubules is described as microtubule nucleation potential (MNP), present in the above-defined protein complexes. It also seems that and has specific evidence for the presence of genetic material in the centrioles. It is thought that the centrosome has evolved in the metazoan lineage of the eukaryotic cells. The origin of the centrosome takes place through the replication of centrioles themselves, which are semi-autonomous.
Function of Centrosome
The centrosome functions include it is implicated in the formation of the basal bodies, spindle fibers, cilia, and flagella. At the time of cell division, the centrioles separate and move to opposite poles of the nucleus, a spindle is formed between them, and the chromosomes get arranged in the equator. It also mediates the contraction of spindle fibers. Therefore, the centrosome plays a significant role in cell division, maintaining the number of chromosomes during cell division.
During mitosis, the centrosome assists in organizing the microtubule. They also regulate the movement of microtubules by tubulin proteins and overall cytoskeletal structures. Therefore, the centrosome is a crucial organelle for giving a proper structure to the cell.
Centrosome and Kinetochore
The kinetochore is a disc-shaped structure associated with the centromere and pulls the sister chromatids apart during cell division. One centromere consists of two kinetochores. It is required for the accurate segregation of chromosomes during cell division. It is a protein complex on the chromosomes where spindle fibers get attached during cell division. At the same time, a centrosome is just an organelle that mediates the microtubule-organizing proteins, which consist of two centrioles.
Conclusion
A centrosome is an organelle near the nucleus of a cell, surrounded by a set of centrioles that give rise to spindle fibers during cell division. Centrosomes play numerous functions in the cell. It overall maintains its structure, develops cytoskeletal rearrangement, and the formation of microtubule proteins like tubulin. It is the major microtubule-organizing center in the eukaryotic cells. It also contains several proteins like centrin, pericentrin, ninein, and centrosomin. It is much like DNA in animal cells so that one centrosome from the parent cell gets transferred to each daughter cell. A centrosome is not found in plants and fungi.
