noun, plural: flagella
(2) (botany) A runner
Relating to a flagellum or to the extremity of a protozoan
A flagellum is a whip-like appendage on the cell body of certain cells. It is primarily involved in locomotion. It helps move the cell through an aquatic environment, for instance, by propulsion. There are three types of flagella that are described: bacterial flagella, archaeal flagella (archaella), and eukaryotic flagella. In bacteria, the flagella are helical filaments made up of the protein, flagellin, and rotate like screws. In archaea, the flagella also consist of filaments protruding outside the cell. Nevertheless, the filaments rotate as a single assembly as opposed to bacterial filaments that rotate independently. In eukaryotes, such as in cells of animals, plants and protists, they are made up of microtubules surrounded by the plasma membrane and enable the cells to move in a whip-like fashion.
Some flagella are not used for movement but in sensation and signal transduction by various cell types, e.g. rod photoreceptor cells of the eye, olfactory receptor neurons of the nose, kinocilium in cochlea of the ear.
Word origin: Latin, diminutive of flagrum, whip