* Cilia are short, hair-like projections that beat in a coordinated, wave-like motion. They are found in large numbers on the surface of some cells, such as those lining the respiratory tract, where they help to move mucus and debris.
* Flagella are longer, whip-like structures that propel cells through a fluid medium. They are typically found in single numbers or in pairs, and are used for movement by sperm cells and some bacteria.
Both cilia and flagella are composed of microtubules, which are protein filaments that are arranged in a specific pattern. The movement of these structures is powered by the motor protein dynein, which uses ATP to generate movement.
