Final answer:
The electron transport carriers actively pump hydrogen ions (H+) into the outer membrane compartment, setting up a concentration gradient called the proton motive force.
Step-by-step explanation:
The electron transport carriers actively pump hydrogen ions (H+) into the outer membrane compartment as they shuttle electrons, setting up a concentration gradient known as the proton motive force. This proton motive force is essential for the production of ATP through chemiosmosis.