Cell Biology
Flagellum
[object Object]
A whip-like appendage that enables cell movement. Bacterial flagella rotate like propellers at up to 1,000 RPM; eukaryotic flagella wave back and forth. Plural: flagella. The cellular equivalent of a single-purpose motor.
Biological Context
Bacterial flagella are rotary motors—among the most efficient machines in nature. They contain 40+ protein components including the rotor, stator, and drive shaft. They can rotate at 200-1,000 RPM (some species up to 100,000 RPM) and reverse direction within a quarter turn. Eukaryotic flagella (like sperm tails) use a different mechanism—they bend in waves rather than rotate. Both enable directed cell movement and chemotaxis (movement toward or away from chemicals).