Flagelle

Flagelle are whip-like appendages found on the surface of many microorganisms, including bacteria, archaea, and some eukaryotic cells. Their primary function is motility, enabling these cells to move through liquid environments. The structure of flagella varies significantly between different types of organisms. Bacterial flagella are long, helical filaments composed of a protein called flagellin. They rotate like a propeller, powered by a complex molecular motor embedded in the cell membrane. Archaean flagella, though similar in function and appearance, are structurally distinct and assembled in a different manner. Eukaryotic flagella, found in organisms like Euglena and sperm cells, are more complex, possessing a 9+2 arrangement of microtubules. They move in a whip-like or undulating fashion. The presence and number of flagella can vary, with some cells having one, many, or none. These organelles play a crucial role in processes such as nutrient acquisition, escaping predators, and finding suitable environments for growth and reproduction.