Proton gradients (chemiosmosis)

[randomkeyboard]

Hi, I've been set an essay about chemiosmosis - to describe the key features of the system and the 'various ways this can be used'
Now, I get that its all about the proton gradient coupled with the ETC, but various ways?? I don't understand what else it can be used for! Any help would be really appreciated thankyou!

[canalon]

-flagellar movement in bacteria
-search for proton pump in google scholar, tons of examples