What is the electron donor for PSII and the key process at PSII?

What is the electron donor for PSII and the key process at PSII?

• A. Water is reduced to hydrogen peroxide at PSII
• B. CO2 is fixed to RuBP at PSII
• C. Water is split by the water-splitting complex in PSII (photolysis) to replace electrons, releasing O2
• D. NADP+ is reduced to NADPH at PSII

Answer: (C)

The main idea is that PSII gets its electrons from water and uses light to split water in a process called photolysis. The water-splitting complex oxidizes water, providing electrons to replace those lost by the PSII reaction center, and in the process releases O2 as a byproduct. This is the source of electrons that drive the initial step of the light-dependent reactions and set up the whole photosynthetic electron transport chain. The other statements don’t fit PSII: CO2 fixation happens later in the Calvin cycle in the stroma, NADP+ is reduced to NADPH at PSI, and water is not reduced to hydrogen peroxide at PSII.

The main idea is that PSII gets its electrons from water and uses light to split water in a process called photolysis. The water-splitting complex oxidizes water, providing electrons to replace those lost by the PSII reaction center, and in the process releases O2 as a byproduct. This is the source of electrons that drive the initial step of the light-dependent reactions and set up the whole photosynthetic electron transport chain. The other statements don’t fit PSII: CO2 fixation happens later in the Calvin cycle in the stroma, NADP+ is reduced to NADPH at PSI, and water is not reduced to hydrogen peroxide at PSII.