the membranes of the organelles ie chloroplast in photosynthesis and mitochondria in respiration hav small units known as Atpsynthases.these help in the synthesis of ATp.the gradient for the synthesis of ATP is provided by the transfer of protons across the membrane.the stability of the gradient is due to the impermeability property of the membrane.more over the membrane has many subunits that help in efficient transfer of electorns and protons.
