The movement of cilia and flagella can be explained on the basis of three types of mechanisms:
- Cilia and flagella are whip-like motile organelles present in a wide variety of eukaryotes. The force is exerted at its base.
- When the contraction takes place due to propagating wave contract at the inner curvature alternately forcing the opposite sides to bend the cilium or flagellum from side to side.
- When the thin filament move past one another to produce a curvature in a sliding manner similar during muscle contraction. These filaments do not change their shape.
When dynein proteins are unrestrained (the micro-tubules are not held together with cross-linking proteins) they are able to “walk” down the adjacent micro-tubule, allowing the micro-tubules to slide past one another. When dynein proteins are restrained due to micro-tubule cross-linking as shown in the figure below, the micro-tubules cannot slide and instead bend as seen in cilia and flagella. The wave-like motion of cilia and flagella arises from this restrained movement as the micro-tubules bend in one direction and then the other.