Which of the following combinations is required for chemiosmosis?

Chemiosmosis requires a membrane, a proton pump, a proton gradient and ATP synthase. Energy is used to pump protons across a membrane, to create a gradient or a high concentration of protons within the thylakoid lumen. ATP synthase has a channel that allows diffusion of protons back across the membrane. This releases enough energy to activate ATP synthase enzyme that catalyses the formation of ATP.

(1) Though proton pump is required for chemiosmosis, electron gradient and NADP synthase are not necessary for
chemiosmosis.
(3) Membrane, proton pump and proton gradient are necessary for chemiosmosis but NADP synthase is not required.
(4) Proton pump and ATP synthase are required for chemiosmosis, but not electron gradient.