Consider these events of photosynthesis. 1. Light energy excites electrons. 2. Water molecules are split. 3. NADPH is formed. In which locations do each of these events occur?

Light first excites electrons in photosystem II. Water is split at photosystem II to replace those electrons, releasing oxygen and hydrogen ions. The electrons then pass through the transport chain to photosystem I, where they are re-energized and ultimately help form NADPH. Therefore, the correct choice is “1. photosystem II 2. photosystem II 3. photosystem I.”

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