Cengage Microbiology Practice Test

The basic idea is chemiosmotic coupling: the proton motive force is an electrochemical gradient created by pumping protons across a membrane during respiration. This gradient powers ATP synthase, a membrane-bound enzyme. Protons flow back through the Fo portion of ATP synthase, turning its rotor. That mechanical motion drives the conformational changes in the F1 catalytic sites, catalyzing the formation of ATP from ADP and inorganic phosphate. This is how energy captured from nutrients ends up stored as ATP. Other enzymes listed don’t use this proton flow to make ATP. RNA polymerase builds RNA using nucleotides, not energy from a proton gradient. DNA polymerase builds DNA using dNTPs and energy from nucleotide hydrolysis, not from proton motive force. Topoisomerase alters DNA topology without ATP synthase’s rotor mechanism.