Do Animal Cells Have Centrioles: 5 Facts You Should Know

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In this article, let’s see 5 facts about centrioles in animal cells.

Centrioles are cylindrical-shaped structures present in eukaryotic animal cells and small plant cells. The main function of the Centrioles is to form spindle fibers during cell division

Do animal cells have Centrioles?

Centrioles are present only in eukaryotic animal cells and they are absent in prokaryotic cells. Centriole plays an important role in organizing the microtubules during cell division and ensures that the daughter cells get the correct number of chromosomes.

Cell organelles like cilia and flagella are formed by the centrioles. The Centrioles are pair of self-replicating organelles that are present near the nuclear envelope.

Do only animal cells have Centrioles?

Centrioles are not only present in animals but also present in the lower plant cells like bryophytes, cycads, charophytes, and seedless vascular plants. The Centrioles are present inside the centrosome that is located near the nucleus.

In lower plants, the Centrioles are formed during spermatogenesis and also produce cilia during the interphase of the cell cycle.

 Flagella are thread-like structures that protrude from the plasma membrane and help in locomotion. Cilia are short hair-like structures present on the outer surface of the cell and it moves the entire cell or certain substances.

do animal cells have centrioles
Centriole in the animal cell from Shutterstock

Why Centrioles are only found in animal cells?

Centrioles play an important in animal cells during cell division because they pull the cell into two new daughter cells.

During mitosis, the Centrioles control the formation of spindle fibers and separate the chromosomes.

What is the structure of the Centrioles?

The Centrioles are a pair of barrel-shaped organelles that are present inside the centromeres in the cytoplasm near the nucleus. In animal cells, the Centrioles are 150-500nm long and 250nm in diameter protein-based structures with nine triplets of microtubules.

In the cilia and flagella, the Centrioles are present at the base called basal bodies that consists of a central matrix from which spokes radiate in form of a cartwheel.

The centriole consists of three main parts:

  • Distal part
  • Central core
  • Cartwheel

Distal part:

The distal part consists of either a double or triplet set of microtubules. It is divided into distal and sun-distal parts. The eukaryotic cells consist of nine distal appendages and the sub-appendages vary according to the type of cell and its function.

The distal appendages that resemble the turbine blades are arranged symmetrically and are attached to the distal end of the Centrioles. The sub-distal appendages are attaché to three triplets and form right angles to the surface of the centriole.

Central core:

Microtubule triplets which are 250nm in length are attached to the central core of the Centriole. It contains a Y-shaped linker and a barrel-like structure located in the inner core.

Cartwheel:

The cartwheel is made up of a central region that consists of nine spokes radiating from it. Each filament is connected to the A-tubule of the microtubule with the help of a pinhead. The pinhead is an important structure of the cartwheel and it poses a hook-like structure and linkers between the microtubule and pin body. The cartwheel creates a nine-fold symmetry in the organelle and strengthens the arrangement of the triplet microtubule.

structure centrioles infographics vector illustration 600w 519790684
Structure of centriole from Shutterstock

What is the function of animal cell Centrioles?

The Centrioles in the animal cell have two main functions:

  • Cell division
  • Cilia and flagella formation

Role of centriole in cell division

In cell division, the Centrioles are directly linked to their own duplication. Two Centrioles are present during the formation of two new cells and they duplicate along with DNA replication. The centromere divides during cell division and causes the Centrioles to separate.

During the S phase, a new centriole gets assembled from the protein components and is referred to as procentriole. At this stage, The Centrioles are not mature at this stage and the juvenile Centrioles get aligned to the right angle of the pre-existing Centrioles during late mitosis. The proximal end of the pro-centriole slowly reaches the surface of the mature centriole and this is known as engagement. This is maintained till the interphase of the cell cycle.

 The centrosome is formed by the protein matrix, procentriole material, and mature Centrioles. During the cell division, the centromere split and moves to the opposite poles of the cell and gradually grow towards the center of the cell as microtubules.

The spindle fiber grows towards the chromosome and gets attached to the protein complex kinetochore present in the centromere. After the attachment, the spindle fiber pulls the chromosomes and during the anaphase, the sister chromatids are pulled to the opposite poles of the cell and they become independent chromosomes.

anaphase cell division cycle 600w 2065936793
Microtubule formation of centriole during cell division from Shutterstock

Role of centriole in flagella and cilia formation:

The centriole plays an important role in the formation of cilia and flagella. The flagella and cilia help in locomotion and to receive signals and respond to the stimuli.

The cilia are composed of a microtubule structure known as axoneme and they are two types of cilia

  • Motile cilia
  • Primary cilia

The motile cilia consist of 9+2 microtubule structures whereas it is absent in non-motile cilia as they are primarily involved in signal transduction and also contribute to the development and differentiation of cells.

The Centrioles get converted into basal bodies and later develop into cilia. The ciliary vesicles interact with the mother centriole and cap the vesicles to the distal end of the centriole before they migrate to the surface of the cell and get attached to the plasma membrane.

The transition zone is the region between the axoneme and the basal body that contains a Y-shaped Bridge that links the ciliary membrane and microtubule. This junction decides which material has to be passed through the cilium.

Conclusion:

Centrioles are paired barrel-shaped structures that are present in animal cells and lower plant cells. They play an important role in cell division and flagella formation.

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