Cilia and flagella are composed primarily of a protein called tubulin, which assembles into structures known as microtubules. These microtubules are arranged in a specific pattern that forms the core of cilia and flagella, notably in a ‘9+2’ arrangement, consisting of nine pairs of microtubules surrounding two central microtubules.
In more detail, cilia and flagella originate from a structure called the basal body, which anchors them to the cell membrane. The microtubules extend from the basal body and create the whip-like structures we observe. This organization allows for their primary function of movement—cilia move in a coordinated manner to propel cells or move fluids across their surface, while flagella typically function to propel a cell through a liquid environment.