Which of the following processes result in development of a proton gradient across the thylakoid membrane during photosynthesis? i. Release of protons into the lumen of the thylakoid by plastoquinone ii. Consumption of protons in the stroma during the reduction of NADP ^+ iii. Release of protons into the lumen of the thylakoid by ATP synthase iv. Release of protons into the lumen of the thylakoid by water splitting r

Step-by-step solution

During photosynthesis, the proton gradient across the thylakoid membrane is developed due to the following processes: Plastoquinone acts as a hydrogen carrier, transferring electrons from PSII to the cytochrome b₆f complex while simultaneously pumping protons from the stroma into the thylakoid lumen. This increases the proton concentration in the lumen. The enzyme NADP reductase is located on the stroma side of the membrane. The reduction of NADP ^+ to NADPH consumes protons from the stroma, which decreases the pro