Photosystem I

Photosystem I is where the cell's reducing power is generated. When light quanta are absorbed by P700, energy-rich electrons are ejected from its reaction centre and passed down a chain of electron carriers to NADP+. Combined with protons made available by the water-splitting reaction at PS-II, this reduces NADP+ to NADPH2. Because this NADPH2 supplies the hydrogen that will be used to reduce CO2 in the dark reactio …