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Flagella are whip-like structures that enable locomotion in certain cells. In prokaryotes, like bacteria, flagella have a simple structure composed of a protein called flagellin. Prokaryotic flagella consist of three parts: the filament, which is the long whip-like part; the hook, which connects the filament to the basal body; and the basal body itself, which serves as the anchoring and rotation mechanism.

Eukaryotic flagella, however, are more complex. They are encased in an extension of the cell membrane, which means they are actually continuations of the cell's outer layer. Structurally, these flagella are supported by microtubules made of the protein tubulin. These microtubules are arranged in what's known as a '9+2' pattern - nine pairs of microtubules form a ring around two central microtubules. This intricate design is vital for the distinct motion of eukaryotic flagella.

The movement of flagella is how cells swim through liquid environments. Prokaryotic flagella move by rotating like the propeller of a boat. This rotation is powered by a flow of ions across the cell's membrane, which is converted into motion by a series of proteins that act like a motor at the flagella's base.

In contrast, eukaryotic flagella move through a bending process. This bending is caused by dynein arms, which are motor proteins that cause adjacent microtubules to slide against one another, creating a whip-like motion. This sophisticated sliding mechanism is coordinated in such a way that it generates the forward movement of cells, like sperm or certain algae and protozoa.

Flagellin and tubulin are the main protein components of prokaryotic and eukaryotic flagella, respectively. Flagellin molecules come together to form the helical filament of a prokaryotic flagellum. It's these flagellin proteins that give the flagellum its structural strength and helical shape, which are crucial for the effectiveness of its rotational movement.

On the other hand, tubulin is the building block of microtubules that form the internal 'skeleton' of eukaryotic flagella. There are two forms of tubulin: alpha and beta. These link together to form dimer units, which then join end to end to form the microtubules. The dynamic assembly and disassembly of tubulin in microtubules are fundamental for the bending motion seen in eukaryotic flagella, demonstrating a more intricate process compared to the simpler mechanism found in prokaryotes.