Question

Certain drugs act as ionophores, these drugs cause the thylakoid membrane to become permeable to hydrogen ions (H+). This means that when the drug is present H+ can simply pass through the membrane on their own without a protein like a nonpolar molecule does normally.   When you treat chloroplasts with this ionophore, the light reactions stop making ATP but continue to make NADPH. Explain this result.

Answer 1

the sunlight is absorbed during photosynthesis and the energy trapped will be used for the photolysis of the water releasing electron and protons (H+).

the electrons generated during photolysis travel through various molecules of photosystem I and II and finally they reach to NADP+ and it will be reduced to NADPH.

the proton generated in photolysis will be accumulated in the lumen of thylakoid producing a proton gradient across the thylakoid membrane (inside H+ concentration is high than out side) and they are pumped out through ATP synthase protein which produce ATP.

in presence of ionophore the protons from the lumen will be leaked out because these ionophore make the thylakoid membrane permeable. so there is no proton gradient inside the thylakoid lumen, hence ATP can not be synthesized after ionophore treatment.