Answer:
water
Step-by-step explanation:
The light energy trapped in the chlorophyll a reactive molecule of Photosystem II releases electrons at a higher energy level. These electrons are replaced in the chlorophyll a molecule by electrons that come indirectly from water molecules that are cleaved and also release protons (H +) and oxygen gas. The electrons pass from the primary electron acceptor, along an electron transport chain, at a lower energy level, the reaction center of Photosystem I. As they pass along this electron transport chain , a proton gradient is formed from which ATP is synthesized. The light energy absorbed by Photosystem I releases electrons to another primary acceptor. From this acceptor, electrons are transferred by other transporters to NADP + and NADPH is formed. The electrons removed from Photosystem I are replaced by those from Photosystem II. ATP and NADPH represent the net gain of the reactions that capture energy.