Centriole, cilia and and flagella:
Aim of the Article:
After reading this article you will be able to answer the top 5 questions which are:
1. What is a Centriole and centrosome simple definition?
2. What are the structure and Functions of Centriole?
3. What are structure and functions of cilia and flagella?
4. What is the difference between centriole and Cilia/Flagella?
5. What is 9+0 and 9+2 arrangement in cilia/ flagella and centriole?
The cytoskeleton is made up of three types of proteins, which are;
1. Microtubules
2. Microfilaments
3. Intermediate filaments.
Microtubules help in the formation of the following structures:
1. Centriole
2. Basal bodies
3. Cilia and Flagella
(Today we will discuss these three structures)
Centriole:
Definition of Centriole:
They are self-replicating, cylindrical, non- membranous, hollow organelle present in Cytoplasm, near the nucleus, exist in pair form and are both placed at a right angle to each other.
Presence of Centriole:
They are present in an animal cells, microorganisms and lower plant cells but absent in higher plant cells.
Location of Centriole:
Present in Cytoplasm near the outside of the nucleus.
Centrosome:
The region where Centriole is present is known as Centrosome.
Structure Of Centriole:
They occur in pair form and lie at a right angle with each other. Each Centriole consist of NINE Microtubules and each microtubule is further composed of three Microtubules (Nine triplets of Microtubules). So one Centriole consists of a total of 27 arrays of Microtubules. There are no central Microtubules so we can say that there are 9+0 arrangements of Microtubules.
Functions of Centriole:
Just before cell division, its Centriole duplicate and one pair migrate to the opposite side of the nucleus and spindle fibers formed by the Centriole.
Spindle fibers are structure that helps in separation and partition of chromosomes during cell division. So we can say that Centriole help in cell division.
Basal Bodies:
They are present within the Cytoplasm of the ciliated and flagellated cell. Made up of Microtubules. They form the base of the cilia and flagella. They are similar to the structure of Centriole. They help in the organization of cilia and flagella.
Cilia and Flagella:
They are microscopic hair or thread-like motile structures. They present extracellular which means present outside of the cell. They originated intracellularly which means arise inside from cell, the originating point is known as the basal body. Cilia are small hair-like while flagella are long thread-like structures. Ciliated cells contain many short cilia while flagellated cells contain one or two long flagella.
Structure of Cilia and Flagella:
They are also made up of Microtubules like Centriole but in this case, nine doublets of Microtubules are present and a pair of Singlet Microtubules at the center which is known as Axoneme. So a pair of singlet Microtubules are present at the center (Axoneme) so we can say that there is 9+2 arrangement of Microtubules. The bundle of Microtubules and Axoneme (Central pair of singlet Microtubules) are surrounded by a plasma membrane.
The function of cilia and flagella:
The function of Cilia and Flagella In animals:
1. In humans, Cilia is present on cells lining the trachea, where it helps in the prevention of mucous and dirt from entering the lungs.
2. Cilia is also present in the fallopian tube (part of the female reproductive system) which helps in the movement of eggs between the ovary and uterus.
3. Human sperm cells have flagella by which they move from one place to another.
The function of cilia and flagella in microorganisms:
Cilia and flagella help in the movement of microorganisms from one place to another.
Difference between Centriole and Cilia/Flagella:
1. Centriole exists in pair form while cilia and flagella may be more than two.
2. The centriole is present inside of the cell while cilia/ Flagella are present outside of the cell.
3. Centriole consists of NINE TRIPLETS of microtubules while cilia and flagella consist of Nine Doublet of microtubules.
4. In Centriole, there are no central microtubules while in cilia and flagella there is a pair of singlet microtubules (Axoneme).
5. There is 9+0 arrangement of Microtubules in Centriole while 9+2 in cilia and flagella.
6. There is a total of 27 (9x3) microtubules in a single Centriole while in single cilia and flagella there are 20 (9x2 +2) microtubules.
7. Centriole help in cell division while cilia/ flagella help in movement.
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