In the light-dependent reactions of photosynthesis, which molecule serves as the ultimate source of electrons to replace those lost by Photosystem II?
Q1. In the light-dependent reactions of photosynthesis, which molecule serves as the ultimate source of electrons to replace those lost by Photosystem II?
Answer: Water
Explanation: Water undergoes photolysis to provide electrons to PS II; CO2 provides carbon for glucose but does not act as an electron donor.