Centrioles: Definition, Structure, Function, Parts, Roles

Edited By Irshad Anwar | Updated on Jul 02, 2025 07:36 PM IST

Centrioles are cylindrical organelles made up of a protein called tubulin.

Tiny construction specialists are indispensable for the processes of cell division and construction.

What is Centriole?

Centrioles are cylindrical organelles of eukaryotic cells which are made of microtubule triplets of a particular kind. It has a critical function in cell division, where they position microtubules to create the spindle fibres during mitosis and meiosis; this is to guarantee the proper distribution of chromosomes. In the same measure, they anchor sites for ciliation and fractionation, which are crucial for cell locomotion and instinctual apparatuses like cilia and flagella.

Centrioles: Definition, Structure, Function, Parts, Roles

Centrioles are usually double, provided they are in the centrosome area which is close to the nucleus of the cell. Like replication, their reproduction is very controlled, having clear and strict structures that are fundamentally important for cell health and functionality in different species and at different stages of development.

Centrioles Structure

The structure of centrioles is discussed below:

Basic Structure

Centrioles are cylindrical structures usually ranging in diameter to about 200 nm and in length to 500 nm in the human cell.

Each centriole is made of nine triplets of microtubules disposed of in a circle, thus it represents a barrel shape.

Diagram of Centriole Structure

Ultrastructure

Centrioles are comprised of microtubule triplets; each of the triplets has a complete microtubule known as the Atubule and two demarcated microtubules, the Btubule and the Ctubule.

Tubulin proteins are the main chromosome of centrioles; however, certain proteins like pericentrin and centrin are involved in the stability of centrioles.

Diagram showing detailed microtubule arrangement

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Centrioles Function

The functions of centrioles are discussed below:

Role in Cell Division

One of centrioles' main functions is in the formation of spindle fibres, which is instrumental in the separation of chromosomes during the division period.

In mitosis and meiosis, centrioles play a significant role in assembling the spindle apparatus thereby affecting proper orientation and segregation of chromosomes as well as cell division.

Formation of Cilia and Flagella

Centrioles act as basal bodies to help in the process of growth of cilia and flagella which are important in the movement and sensory organelles of the cell.

Organisation of the Mitotic Spindle

Centriole replication is semiconservative in which each new pair of centrioles consists of one old, or mother, centriole, and one new, or daughter, centriole.

Diagram of centrosome organisation during cell division

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Centriole Duplication and Cycle

The centrosome duplication is discussed below:

Duplication Process

Replication starts in the S phase of the cell cycle for new centrioles to start forming alongside older ones.

Phases:

In the G2 phase, the new centrioles begin to grow and reach maturation during this phase. In the Mphase, a centriole pair gets separated so that each of the two daughter cells gets a centrosome.

Diagram of centriole duplication cycle

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Regulation of Duplication

Proteins, including SAS6 and STIL, are important in the start and correct development of new centrioles in the course of duplication.

The centrosome cycle is tightly controlled and accurately coordinated with the cell cycle for achieving accurate centriole duplication and transportation, which is very important for genome stability as well as the efficient functioning of the cell.

Centrioles and Centrosomes

Centrioles and Centrosomes are discussed below-

Definition of Centrosome

The centrosome is a small organelle located in the cytoplasm and consists of two centrioles surrounded by a granule material called pericentriolar material (PCM). Serving as the primary focusing centre of the microtubules in the cell, it is primarily responsible for the arrangement of microtubules and their segregation during cell division.

Diagram of centrosome with centrioles

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Relationship Between Centrioles and Centrosomes

Centrioles are part of centrosomes and play a crucial role in centrosome duplication.

Role in microtubule organisation

Centrioles are also involved in the organisation of microtubules in the centrosome contributing to the formation of mitotic spindle during cell division and structural framework of the cell.

Abnormalities and Diseases Related to Centrioles

The abnormalities are discussed below:

Centriole Defects

Damage to centrioles causes improper cell division and aneuploidy or genomic instability, which are related to different diseases. Also, centriole ultrastructure alterations may influence cilia development and the latter’s performance, which results in numerous cellular abnormalities.

Defects are associated with several diseases such as microcephaly, which is a result of reduced brain size by improper cell division, and different types of cancer which involve abnormal cell division and instability of the genome.

Centrosome Amplification

Centrosome duplication in which at least one cell has more than two centrosomes can cause multipolar mitoses that in turn cause chromosome segregation disorders causing aneuploidy. This condition is frequently detected in cancer cells and is linked with the advancement of the disease and worse outcomes.

Diagram showing abnormal centrosome amplification

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Frequently Asked Questions (FAQs)

1. What are centrioles and their function?

Centrioles are tubelike organelles made up of microtubules triplet arrangements in order. They are vital in cell division by assisting the formation of the mitotic spindle as well as in the formation of cilia and flagella.

2. How do centrioles duplicate?

Centrioles are thus able to undergo semiconservative replication in the S phase during the cell cycle. This is the process of nucleation where a new centriole or “daughter centriole” forms beside each current “mother centriole”, especially in the G2 phase of the cell cycle, where the elongation occurs and finally in mitosis separates.

3. What is the relationship between centrioles and centrosomes?

Centrosomes are composed of two centrioles and a pericentriolar material (PCM). Centrioles are an essential structural part of centrosomes which in turn serve as the major MTOCs in the cell being involved in the organization of microtubules and the process of cell division.

4. What diseases are associated with centriole defects?

Abnormalities in centrioles or their defective structures are associated with several diseases: microcephaly that occurs due to improper cell division and shrinkage of the brain size and, in cancer, centrosome amplification accompanied by inefficient and chaotic cell division and tumorigenesis. Some of the associated disorders include ciliopathies; which are characterized by the malfunction of cilia and present with multiple manifestations.

5. How are centrioles involved in cell division?

In the process of cell division, they play a part in the formation of the spindle apparatus from the microtubules that are used to sort out the chromosomes in the daughter cells. Checkpoint proteins play a crucial role in the right segregation of chromosomes during the process of mitosis and meiosis, which is imperative for the correct maintenance of the genomic stability of a cell.

6. What is centriole amplification and why is it significant?

Centriole amplification refers to the presence of more than two centrioles in a cell. This can occur due to errors in centriole duplication or cell division. Centriole amplification is significant because it can lead to the formation of multipolar spindles during mitosis, resulting in chromosome missegregation and genomic instability. This phenomenon is often observed in cancer cells and can contribute to tumor progression.

7. What proteins are important for centriole structure and function?

Several key proteins are crucial for centriole structure and function. These include:

8. How do centrioles differ between plant and animal cells?

Most animal cells contain centrioles, while most plant cells do not. Plant cells typically use other structures to organize their microtubules during cell division. However, some lower plants like mosses and ferns do have centrioles, while higher plants have evolved to function without them.

9. Can cells function without centrioles?

Yes, many cells can function without centrioles. Most plant cells and some animal cell types lack centrioles but still divide successfully. In these cases, other structures take on the role of organizing microtubules during cell division. This demonstrates that while centrioles are important in many cells, they are not universally essential for cell function.

10. What is the evolutionary significance of centrioles?

The evolutionary history of centrioles provides insights into cell biology and organism development. Centrioles are found in most animal cells and some lower plants, but are absent in higher plants and fungi. This suggests that centrioles evolved early in eukaryotic evolution but have been lost in some lineages. Studying centrioles across different organisms helps us understand how cellular structures adapt and change over evolutionary time.

11. How do centrioles replicate?

Centriole replication occurs during the S phase of the cell cycle. A new centriole, called a procentriole, begins to form perpendicular to each existing centriole. The procentriole elongates and matures throughout the cell cycle, becoming a full centriole by the next cell division.

12. What is the relationship between centrioles and the cell cycle?

Centrioles are closely linked to the cell cycle. They replicate during S phase, separate during G2 phase, and play a crucial role in mitosis by organizing the mitotic spindle. The proper duplication and function of centrioles are important for maintaining genomic stability, as abnormalities in centriole number or structure can lead to errors in chromosome segregation.

13. What happens to centrioles during meiosis?

During meiosis, centrioles behave similarly to mitosis, but with some key differences. In meiosis I, centrioles organize the spindle for the first division. After meiosis I, centrioles do not duplicate before meiosis II. Instead, the existing centrioles separate and organize the spindle for the second meiotic division. This ensures that the resulting gametes have the correct number of centrioles.

14. How do centrioles maintain their fixed length?

Centrioles maintain a consistent length through a balance of microtubule addition and removal at their distal ends. Proteins like CPAP promote microtubule growth, while others like Kif24 and CP110 cap the distal end and prevent overgrowth. This regulated process ensures that centrioles maintain their characteristic length, which is important for their proper function in cell division and cilia formation.

15. How do centrioles contribute to asymmetric cell division?

In asymmetric cell division, centrioles can play a role in determining the axis of division and the unequal distribution of cellular components. The older (mother) centriole often has different properties than the younger (daughter) centriole, which can influence spindle orientation and the inheritance of centrioles and associated proteins in the resulting daughter cells. This is particularly important in stem cell divisions and during development.

16. How do centrioles contribute to cell motility?

Centrioles contribute to cell motility primarily through their role as basal bodies for cilia and flagella. When centrioles migrate to the cell surface and become basal bodies, they serve as the foundation for the growth of motile cilia or flagella. These structures enable cell movement in single-celled organisms and create fluid currents in multicellular organisms, such as in the respiratory tract.

17. How do centrioles contribute to the formation of cilia and flagella?

Centrioles can migrate to the cell surface and become basal bodies, which are the base structures for cilia and flagella. The basal body acts as a template for the growth of microtubules that form the core of cilia and flagella, enabling cell movement or the creation of fluid currents around the cell.

18. How do centrioles contribute to cell polarity?

Centrioles help establish cell polarity by influencing the organization of the cytoskeleton. When centrioles migrate to form basal bodies for cilia or flagella, they create a clear axis in the cell. This polarization can influence cell shape, movement, and the distribution of cellular components, which is particularly important in processes like cell migration and embryonic development.

19. How do centrioles differ from basal bodies?

Centrioles and basal bodies are essentially the same structure in different cellular contexts. When centrioles are located near the nucleus and function in cell division, they are called centrioles. When they migrate to the cell surface and serve as the base for cilia or flagella, they are called basal bodies. The main difference is their location and function within the cell.

20. How do centrioles relate to the primary cilium?

The primary cilium is a single, non-motile cilium present in many cell types. It forms when a centriole migrates to the cell surface and becomes a basal body. The primary cilium acts as a cellular antenna, involved in various signaling pathways. Understanding the relationship between centrioles and primary cilia is crucial for comprehending various developmental processes and diseases associated with ciliary dysfunction.

21. What is the basic structure of a centriole?

A centriole is a cylindrical structure composed of nine triplets of microtubules arranged in a ring. Each triplet consists of one complete microtubule (A-tubule) and two partial microtubules (B- and C-tubules). This arrangement is often described as a "9+0" structure, referring to the nine outer triplets and the absence of central microtubules.

22. What is the "9+0" structure of centrioles referring to?

The "9+0" structure refers to the cross-sectional arrangement of microtubules in a centriole. The "9" represents the nine triplets of microtubules arranged in a ring around the periphery of the centriole. The "0" indicates that there are no central microtubules in the core of the structure, unlike in cilia and flagella which often have a "9+2" arrangement.

23. How do centrioles differ in structure from the axoneme of cilia and flagella?

While centrioles and the axoneme of cilia and flagella are related structures, they differ in their microtubule arrangement. Centrioles have a "9+0" structure with nine microtubule triplets around the periphery. The axoneme typically has a "9+2" structure, with nine outer doublet microtubules and two central singlet microtubules. This difference reflects their distinct functions: centrioles primarily organize microtubules, while the axoneme enables movement.

24. What is the centrosome, and how does it relate to centrioles?

The centrosome is a cellular organelle that serves as the main microtubule organizing center in animal cells. It typically consists of two centrioles surrounded by a protein-rich matrix called the pericentriolar material (PCM). The centrosome plays a crucial role in cell division and organizing the cell's cytoskeleton.

25. What is the pericentriolar material (PCM) and what is its role?

The pericentriolar material (PCM) is a protein-rich matrix that surrounds the centrioles in the centrosome. It plays a crucial role in microtubule nucleation and anchoring. The PCM contains proteins like γ-tubulin, which helps initiate microtubule growth, and other proteins that regulate centrosome function and cell cycle progression.

26. How do centrioles differ from centrosomes?

Centrioles are structures within the centrosome, while the centrosome is the larger organelle that includes the centrioles. Specifically, a centrosome typically consists of two centrioles arranged perpendicular to each other, surrounded by the pericentriolar material (PCM). The centrosome as a whole functions as the main microtubule organizing center in animal cells.

27. How do centrioles contribute to the formation of the mitotic spindle?

During mitosis, the two centrosomes (each containing a pair of centrioles) move to opposite poles of the cell. From these positions, they nucleate and organize microtubules that form the mitotic spindle. The centrioles, through the surrounding PCM, act as the main microtubule organizing centers, ensuring proper spindle formation and chromosome alignment.

28. What is the function of centrioles during mitosis?

During mitosis, centrioles play a crucial role in organizing the mitotic spindle. They move to opposite poles of the cell and act as organizing centers for microtubules. These microtubules then attach to chromosomes and help separate them during cell division.

29. What is the cartwheel structure in centrioles?

The cartwheel structure is a key component in the early stages of centriole formation. It forms the base of the developing centriole and establishes its nine-fold symmetry. The cartwheel consists of a central hub with nine spokes radiating outward, connecting to the microtubule triplets. This structure is crucial for initiating and maintaining the characteristic centriole architecture.

30. What are centrioles and where are they found in cells?

Centrioles are cylindrical cellular structures found in most animal cells and some lower plant cells. They are typically located near the nucleus in an area called the centrosome. Centrioles play crucial roles in cell division and the organization of cellular structures.

31. What is the relationship between centrioles and centromeres?

While centrioles and centromeres are both important during cell division, they are distinct structures with different functions. Centrioles are part of the centrosome and help organize the mitotic spindle. Centromeres, on the other hand, are regions of chromosomes where sister chromatids are joined and where kinetochores form to attach to spindle microtubules. The interaction between spindle microtubules (organized by centrioles) and centromeres is crucial for proper chromosome segregation.

32. How do centrioles relate to the concept of the microtubule-organizing center (MTOC)?

Centrioles are key components of the primary microtubule-organizing center (MTOC) in animal cells - the centro

33. What is centriole disengagement and why is it important?

Centriole disengagement is the process by which the two centrioles in a centrosome separate from each other. This typically occurs at the end of mitosis or early G1 phase. Disengagement is crucial because it licenses the centrioles for duplication in the next cell cycle. Without proper disengagement, centrioles cannot replicate, which can lead to abnormalities in subsequent cell divisions.

34. How do centrioles contribute to the organization of the Golgi apparatus?

Centrioles, as part of the centrosome, play a role in organizing the Golgi apparatus. The centrosome often positions itself between the nucleus and the Golgi complex. Microtubules nucleated from the centrosome help position and maintain the structure of the Golgi. This spatial organization is important for efficient protein trafficking and secretion in the cell.

35. What is the relationship between centrioles and cancer?

Abnormalities in centriole number or function are often observed in cancer cells. Extra centrioles can lead to multipolar spindles during mitosis, resulting in chromosome missegregation and genomic instability, which are hallmarks of cancer. Additionally, some cancer-associated proteins are involved in centriole regulation. Understanding the role of centrioles in cancer can provide insights into tumor development and potential therapeutic targets.

36. What is the role of centrioles in fertilization?

In many species, centrioles play a crucial role in fertilization. The sperm typically contributes the centriole to the zygote, as most animal eggs lose their centrioles during oogenesis. After fertilization, the sperm centriole duplicates and organizes the first mitotic spindle of the zygote. This paternal inheritance of centrioles is important for initiating the first cell divisions in the developing embryo.

37. How do centrioles contribute to the formation of the midbody during cytokinesis?

During cytokinesis, the final stage of cell division, centrioles play an indirect role in forming the midbody. As the cell divides, the mitotic spindle reorganizes to form the central spindle, which becomes compressed into the midbody. While centrioles don't directly form the midbody, their role in organizing the mitotic spindle is crucial for proper midbody formation and successful cell division.

38. What is the deuterosome pathway of centriole formation?

The deuterosome pathway is an alternative method of centriole formation observed in cells that produce multiple cilia, such as those in the respiratory tract. In this pathway, multiple centrioles form simultaneously around a structure called the deuterosome, rather than duplicating from existing centrioles. This allows for the rapid production of numerous basal bodies needed for multiciliated cells.

39. How do centrioles contribute to the formation of the bipolar spindle in mitosis?

During mitosis, the two centrosomes, each containing a pair of centrioles, move to opposite poles of the cell. From these positions, they nucleate and organize microtubules that form the mitotic spindle. The centrioles, through the surrounding pericentriolar material, act as the main microtubule organizing centers. This ensures the formation of a bipolar spindle, which is crucial for proper chromosome alignment and segregation.

40. How do centrioles contribute to the establishment of left-right asymmetry in embryonic development?

Centrioles play a role in left-right asymmetry through their function as basal bodies for motile cilia. In many vertebrates, a specialized region called the embryonic node contains cells with motile cilia. The coordinated beating of these cilia creates a leftward fluid flow, which is crucial for breaking bilateral symmetry and establishing left-right asymmetry in the developing embryo. This process highlights the importance of centriole-derived structures in developmental patterning.

41. What is the relationship between centrioles and the nuclear envelope during mitosis?

During mitosis, centrioles indirectly influence the breakdown and reassembly of the nuclear envelope. As the centrioles move to opposite poles and organize the mitotic spindle, they contribute to forces that help break down the nuclear envelope at the onset of mitosis. Later, as chromosomes segregate, the reorganization of the spindle, which is anchored at the centriole-containing poles, helps guide the reassembly of the nuclear envelope around the separated chromosomes.

42. How do centrioles contribute to the intraflagellar transport (IFT) system?

While centrioles don't directly participate in intraflagellar transport (IFT), they play a crucial role as basal bodies at the base of cilia and flagella. The basal body, derived from a centriole, serves as the organizing center for the IFT system. It acts as a docking site for IFT particles and motors, and helps regulate the entry and exit of proteins into the cilium. This connection between centrioles and IFT is essential for ciliary assembly, maintenance, and function.

43. What is the role of centrioles in the centrosome cycle?

Centrioles are central to the centrosome cycle, which is coordinated with the cell cycle. The cycle involves several stages: