Natural Photosynthesis Illustration (IMAGE) DOE/Brookhaven National Laboratory Caption Photosystems (PS) I and II are large protein complexes that contain light-absorbing pigment molecules needed for photosynthesis. PS II captures energy from sunlight to extract electrons from water molecules, splitting water into oxygen and hydrogen ions (H+) and producing chemical energy in the form of ATP. PS I uses those electrons and H+ to reduce NADP+ (an electron-carrier molecule) to NADPH. The chemical energy contained in ATP and NADPH is then used in the light-independent reaction of photosynthesis to convert carbon dioxide to sugars. Credit Brookhaven National Laboratory Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.