What is the primary function of a flagellum?

The primary function of a flagellum is propulsion of the cell. Flagella are long, whip-like structures that extend from the cell body and are used by many types of cells, including sperm cells and certain bacteria, to move through liquid environments. The movement generated by the flagellum allows these cells to swim, facilitating processes such as finding food, escaping predators, or reaching specific environments necessary for survival and reproduction.

In contrast, the other options pertain to different cellular functions not associated with the role of flagella. Absorption of nutrients involves cellular structures such as membranes and specialized transport proteins. Formation of cellular structures can refer to processes involving the cytoskeleton or organelles, which build and maintain the physical structure of the cell. Replicating DNA is a process carried out by enzymes during cell division and does not involve flagella. Therefore, the propulsion function of flagella is distinctive and essential for the motility of various cell types.