ATP synthesis according to chemiosmosis hypothesis takes place in both chloroplasts (photophosphorylation) and mitochondria (oxidative phosphorylation). Both these processes need the involvement of:
A membrane (thylakoid membrane or mitochondrial membrane, respectively).
Proton pumps to maintain the pH.
Proton gradient to move the proton across the membrane.
ATP synthase enzyme which is present in F0-F1 particles in mitochondria or CF0-CF1 particles in plastids.