Prokaryotic Flagella

Prokaryotic flagella are long, thread-like structures that protrude from the surface of prokaryotic cells. These structures play a crucial role in movement, helping the cell to swim through liquid environments.

Extension of Cell Membrane or Cell Wall?

The flagella of prokaryotic cells are an extension of the cell membrane, not the cell wall. The flagella are composed of a protein called flagellin, which is synthesized in the cytoplasm and then transported through a channel in the cell membrane to the exterior of the cell.

Structure of Prokaryotic Flagella

The structure of prokaryotic flagella is relatively simple compared to eukaryotic flagella. It consists of three basic parts:

1. Filament: The filament is the long, helical structure that extends from the cell surface. It is composed of many subunits of flagellin protein.

2. Hook: The hook is a short, curved segment that connects the filament to the basal body.

3. Basal body: The basal body is the complex structure that anchors the flagellum to the cell membrane and provides the energy for movement.

Mechanism of Movement

Prokaryotic flagella move in a whip-like motion, rotating at the base to generate the necessary force. The rotation is powered by a proton gradient across the cell membrane, with protons flowing through a channel in the basal body and driving the rotation of a rotor-like structure.

As the rotor turns, it causes the filament to rotate, propelling the cell forward. The direction of rotation can be reversed, allowing the cell to change direction or stop altogether.

Conclusion

In conclusion, prokaryotic flagella are an extension of the cell membrane, not the cell wall. They are composed of a filament, hook, and basal body, and are powered by a proton gradient across the cell membrane. The rotation of the flagella allows the cell to move through liquid environments.