Answer:
The given blank can be filled with motor proteins.
Explanation:
Both cilia and flagella are the projections arising from the cell. They are formed of microtubules and are enveloped by an extension of the plasma membrane. They both are motile and are developed either to move the cell itself or to move substance over or around the cell. The main objective of cilia in mammalian cells is to move mucus, fluid, or cells over the surface.
Flagella are generally found on the gametes, however, they develop the water currents essential for circulation and respiration in coelenterates and sponges. Both cilia and flagella move due to the association of the cytoskeleton with motor protein, dynein. In combination, they are termed as axonemes.