What is the input and output of the light dependent reactions? In what organelle does photosynthesis take place? Where within the chloroplast is all the action during the light dependent reactions? Name two reasons plants use visible light in energy production rather than some other wavelength of the electromagnetic spectrum. What are the two important (to the plant) products of the light dependent reactions? Name a pigment involved in photosynthesis? What is ATP synthase and how does it use protons?