The series of biochemical reactions in photosynthesis that require light energy that is captured by light-absorbing pigments (such as chlorophyll) to be converted into chemical energy in the form of ATP and NADPH.
The light reactions take place on the thylakoid membranes of the chloroplast. The light reactions may either be cyclic or non-cyclic. In cyclic reaction, when the electron is displaced from the photosystem, the electron is passed down the electron acceptor molecules and returns back to photosystem I, from where it was emitted. In the non-cyclic reaction, the photons are captured in the light-harvesting antenna complexes of photosystem II by chlorophyll and other accessory pigments