What structure in a cell is primarily responsible for locomotion?

The structure primarily responsible for locomotion in a cell is flagella. Flagella are long, whip-like appendages that extend from the surface of many types of cells, including sperm cells and certain bacteria. They allow cells to move by rotating or beating in a fluid environment, propelling the cell forward. This movement is vital for various biological processes, such as reproduction in sperm and the movement of single-celled organisms.

While cilia also assist in locomotion, they tend to be shorter and often work in coordinated waves to move fluids or cells across their surface rather than providing the primary means of propulsion. Pseudopods can enable movement for some cells, particularly amoebas, as they extend and retract parts of the cell membrane to engulf food or move toward stimuli. Microvilli, on the other hand, are tiny projections that increase surface area for absorption and do not play a role in locomotion. Understanding these distinctions helps clarify why flagella serve as the main structure for cellular movement.