Centrosome and Centrioles

The centrosome is an organelle that organises the microtubule structures of an animal cell, and it is built around a pair of small cylinders called centrioles.

The centrosome and its centrioles

A centrosome usually contains two cylindrical structures called centrioles. These centrioles are embedded in and surrounded by an amorphous material known as the pericentriolar material. Within the centrosome the two centrioles lie perpendicular to each other — that is, set at right angles.

Internal organisation of a centriole

Each centriole has an internal pattern that resembles a cartwheel. Its wall is made up of nine evenly spaced peripheral fibrils built of the protein tubulin. An important feature is that each peripheral fibril is a triplet — three tubules grouped together — and the adjacent triplets are linked to one another.

The central part of the proximal (inner) region of a centriole is also proteinaceous and is called the hub. Extending outward from the hub, radial spokes made of protein connect the hub to the peripheral triplets, completing the cartwheel appearance. Note that, unlike a cilium or flagellum, a centriole has no central microtubules — its arrangement is described as 9+0 rather than 9+2.

Functions

Centrioles perform two key structural roles: …