In terms of structure and function, how do the flagella of eukaryotic cells differ from those of prokaryotic cells?
The correct answer and explanation is:
Correct Answer:
The flagella of eukaryotic cells differ from those of prokaryotic cells in both structure and function. Eukaryotic flagella are composed of microtubules arranged in a 9+2 pattern and are enclosed by the cell membrane. They move in a whip-like motion using ATP. Prokaryotic flagella are made of the protein flagellin, lack a membrane covering, and rotate like a propeller, driven by a motor powered by ion gradients.
Explanation (300 words):
Eukaryotic and prokaryotic flagella serve the same fundamental purpose: locomotion. However, their structure and the way they generate movement are significantly different due to the differences in cell complexity.
Eukaryotic flagella are long, membrane-bound structures found in organisms such as protozoa, algae, and some animal cells like sperm. Internally, they are composed of microtubules arranged in a “9+2” arrangement—nine pairs of microtubules surrounding two central microtubules. This arrangement is stabilized by proteins like dynein, which act as molecular motors. Dynein uses ATP to slide the microtubules against each other, creating a bending or whip-like motion. Because they are enclosed by the cell membrane, eukaryotic flagella are considered extensions of the cytoplasm.
In contrast, prokaryotic flagella are found in bacteria and are much simpler. They are made of a protein called flagellin and are not covered by the plasma membrane. Prokaryotic flagella have three main parts: the filament, the hook, and the basal body. The basal body acts as a motor, powered by the flow of protons (or sometimes sodium ions) across the cell membrane, which rotates the flagellum like a propeller. This rotary motion is efficient and allows bacteria to move quickly through their environment.
The functional differences reflect the evolutionary divergence between eukaryotes and prokaryotes. Eukaryotic flagella are complex, energy-intensive, and flexible, suited for larger and more complex cells. Prokaryotic flagella are simpler, rigid, and rotation-based, allowing smaller bacterial cells to navigate efficiently in aqueous environments.