So remember, these proton rings rotate as a result of the movement of protons down the electrochemical gradient, and that rotates this entire flagella in the counterclockwise fashion if we're moving forward and clockwise, if we want to change direction. Now, the energy source for our eukaryotic flagella is basically ATP. However, for the case of prokaryotes, we don't use ATP directly. We instead use our proton pumps, so we allow the flow of hydrogen ions down the electrochemical gradient. Now, the structure of eukaryotic flagella is much more complicated than our prokaryotic flagella. For the eukaryotic case, we have a nine plus two arrangement of microtubules.