NEET2026BiologyChapterActual
During the chemiosmotic synthesis of ATP in chloroplasts, which of the following events is directly responsible for the decrease in proton concentration in the stroma?
Options
- ASplitting of water molecules on the inner side of the thylakoid membrane
- BReduction of NADP^+ to NADPH + H^+ by the NADP reductase enzyme
- CFacilitated diffusion of protons through the transmembrane channel of CF₀
- DTransfer of electrons from the cytochrome b₆f complex to plastocyanin
Correct answer
B. Reduction of NADP^+ to NADPH + H^+ by the NADP reductase enzyme
Step-by-step solution
During the chemiosmotic synthesis of ATP in chloroplasts, the proton concentration in the stroma decreases due to two main reasons: 1. The primary electron acceptor (plastoquinone) transfers its electron to a hydrogen carrier, removing a proton from the stroma and releasing it into the thylakoid lumen. 2. The NADP reductase enzyme is located on the stroma side of the thylakoid membrane. It requires both electrons (from PS I) and protons to reduce NADP^+ to NADPH + H^+ . These protons are taken directly from the str