What type of cell structure is primarily responsible for the movement of an entire cell?

The flagellum is the structure primarily responsible for the movement of an entire cell. It is a long, whip-like appendage that protrudes from the surface of some cells, particularly in sperm cells and certain bacteria, allowing them to swim through liquid environments. The motion generated by the flagellum is crucial for mobility, helping the cell navigate toward nutrients or away from harmful substances.

Cilia, while also involved in movement, primarily serve to move fluids or materials across the surface of a cell rather than propelling the entire cell itself. Microvilli increase surface area for absorption and do not assist in cell movement. Ribosomes are essential for protein synthesis within the cell and do not play a role in cellular movement at all. Thus, the flagellum is uniquely adapted for the function of locomotion on the cellular level.