Basic purpose of this lecture is to present on Light Dependent Reaction. By this lecture you can understand the processes of photoionization, photophosphorylation & photolysis; get knowledge of where these processes take place and get knowledge of the difference between cyclic & non-cyclic phosphorylation. The light dependent reactions use light energy to make two molecules needed for the next stage of photosynthesis. The light reactions use solar power to generate ATP and NADPH which provide chemical energy and reducing power to the sugar making reactions.