Ch. 10 Flashcards | Quizlet For each step of photosynthetic electron flow from water to NADP+, drag the appropriate label to indicate whether or not that step requires an input of energy. 1. Water --> P680+ (No energy input required) 2. P680 --> Pq (pastoquinone) (energy input required) 3. Pq ---> P700+ (No energy input required) 4. P700 ---> Fd (ferredoxin)