Centriole
What is centriole?
The centrioles are barrel-shaped organelles that are paired and located in the cytoplasm of the animal cell near the nuclear envelope. Centrioles are vital in organizing microtubules in a group that serves as the cell's skeletal system. They help determine the locations of the cell's nucleus and other organelles within the cell. Each pair of small cylindrical organelles near the nucleus in animal cells is involved in developing spindle fibers in cell division.
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They help the cell during the cell's division and all animals have 2 centrioles. They work during the process of mitosis and meiosis. They could be found in some lower plants such as Chlamydomonas, although they are not present or rarely in many of the fungi, angiosperms (flowering plants), and pinophyta (conifers). They are usually present near the nucleus but are not visible when the cell is not dividing.
Structure of centriole
Centrioles are made up of nine circularly arranged triplet microtubules. A triplet microtubule has a complete microtubule (the A-tubule) onto which two other partial microtubules are assembled (the B- and the C-tubules, respectively).
Centrioles are made up of 9 groups of microtubule triads arranged in a cylindrical shape. The detailed structure of centrioles can be studied only under the electron microscope. These are connected at right angles to each other.
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Edouard van Beneden and Theodor Boveri observed and identified the centrioles for the first time in 1883 and 1888. The structure of duplication of centrioles was first given by Joseph G. Gall and Etienne de Harven in the 1950s.
The embryo of Drosophila melanogaster and C. elegans are exceptions to this organization. The former forms 9 pairs instead of microtubule triplets, whereas the premature embryos and sperm cells of C. elegans have 9 single microtubules. 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 of centriol. 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. An image of a single centriole can be seen below.
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| Structure of centriol |
Functions of centriol
Cells form a complex endoskeleton of microtubules that allows substances to be transported from place to place in the cell.
The products are tagged with special glycoproteins (sugar and protein) that act as signals for specific motor proteins.
These proteins bind to the product, or vesicle, in which the product is stored, and also bind to the microtubule.
Microtubules are arranged on the centriole, of which there are two in each centrosome. Centrioles bind to microtubules that extend from it and contain factors needed to make more tubules.
They help in cell division by forming microtubule organizing centers.
Despite being devoid of DNA, centrioles are capable of forming new centrioles.
Basal bodies give rise to flagella and cilia.
They can be converted into basic bodies.
Of the two centrioles, the distal centriole forms the tail or axial filament.
Let's have some questions on 'Centriole'
Q. What is the function of centrioles in animal cells?
a) Organizing microtubules
b) Controlling DNA replication
c) Regulating cell metabolism
d) Synthesizing proteins
Answer: a) Organizing microtubules
Q. How many centrioles are present in animal cells?
a) 1
b) 2
c) 3
d) 4
Answer: b) 2
Q. Where are centrioles located within the cell?
a) Near the Golgi apparatus
b) Near the cell membrane
c) Near the nuclear envelope
d) Near the mitochondria
Answer: c) Near the nuclear envelope
Q. What is the structure of centrioles?
a) Single circular microtubule
b) Double circular microtubule
c) Nine triplet microtubules
d) Twelve parallel microtubules
Answer: c) Nine triplet microtubules
Q. Who discovered centrioles?
a) Edouard van Beneden
b) Theodor Boveri
c) Joseph G. Gall
d) Etienne de Harven
Answer: a) Edouard van Beneden
Q. Which organelles in animal cells are involved in forming spindle fibers during cell division?
a) Mitochondria
b) Centrioles
c) Golgi apparatus
d) Endoplasmic reticulum
Answer: b) Centrioles
Q. What is the role of centrioles in the formation of basal bodies?
a) Providing structural support
b) Generating energy
c) Regulating cell growth
d) Initiating flagella and cilia formation
Answer: d) Initiating flagella and cilia formation
Q. What is the function of the pericentriolar material?
a) Anchoring microtubules
b) Storing genetic information
c) Facilitating protein synthesis
d) Regulating cellular respiration
Answer: a) Anchoring microtubules
Q. Can centrioles replicate and form new centrioles?
a) Yes
b) No
Answer: a) Yes
Q. Which part of the centriole is responsible for forming the tail or axial filament?
a) Proximal centriole
b) Distal centriole
c) Pericentriolar material
d) Basal body
Answer: b) Distal centriole
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