Flagellum, plural flagella, hairlike structure that acts primarily as an organelle of locomotion in the cells of many living organisms. Flagella, characteristic of the protozoan group Mastigophora, also occur on the gametes of algae, fungi, mosses, slime molds, and animals.

amphitrichous (am-fit¢ re-kus) [amphi- + Gr. thrix hair] having a single flagellum, or a single tuft of flagella, at each end; said of a bacterial cell.

Flagella are filamentous protein structures found in bacteria, archaea, and eukaryotes, though they are most commonly found in bacteria. They are typically used to propel a cell through liquid (i.e. bacteria and sperm). However, flagella have many other specialized functions.

Flagella are primarily used for cell movement and are found in prokaryotes as well as some eukaryotes. The prokaryotic flagellum spins, creating forward movement by a corkscrew shaped filament. A prokaryote can have one or several flagella, localized to one pole or spread out around the cell.

Where Can Cilia and Flagella Be Found? Both cilia and flagella are found in numerous types of cells. For instance, the sperm of many animals, algae, and even ferns have flagella. Cilia can be found in areas such as the respiratory tract and female reproductive tract.

Flagella and cilia consist of 9 fused pairs of protein microtubules with side arms of the motor molecule dynein that originate from a centriole. These form a ring around an inner central pair of microtubules that arise from a plate near the cell surface. The arrangement of microtubules is known as a 2X9+2 arrangement.

The discovery of the cilia was made possible by the development of the microscope; Antweiler [24] tells us that Johannes Ham, a student at Leiden, was the first to observe ciliary movements in man in 1677. This discovery was then confirmed by Van Leeuwenhoek in seminal fluid.

Prokaryotes can have more than one flagella. They serve the same function in both prokaryotes and eukaryotes (to move an entire cell). Cilia are not found on prokaryotes.