Import Question JSON

During photosynthesis, the light energy absorbed by the pigments in the thylakoid membrane drives the transfer of electrons from water to NADP⁺ through a series of electron carriers. This process generates a proton gradient across the thylakoid membrane, with a higher concentration of protons (H⁺) in the lumen and a lower concentration in the stroma. As protons flow back down their concentration gradient into the stroma through ATP synthase enzymes located in the thylakoid membrane, the energy from this movement is harnessed to synthesize ATP from ADP and inorganic phosphate. This process is known as photophosphorylation. In PS II, the energy required for ATP synthesis comes from the proton gradient generated by the electron transport chain between PS II and PS I. The movement of electrons through the electron transport chain drives the pumping of protons from the stroma into the thylakoid lumen, creating a proton gradient that drives ATP synthesis.