Light reactions receive sunlight. In the light-dependent reactions, energy, from sunlight is absorbed by chlorophyll and converted into chemical energy, in the form of the electron carrier molecule NAPD (nicotinamide adenine dinucleotide phosphate) and ATP (Adenosine triphosphate). The light-dependent reactions take place in the thylakoid membranes in the granum within the chloroplast. In light reaction two photosynthetic pigment systems are involved called photosystem I(PSI) and photosystem II (PSII). Each photosystem carries a number of chlorophyll molecules that absorb light energy and produce energized electrons. These electrons are the power of light reactions. These two photosystems absorb different light with different wave light PSI absorbs 700 nm wavelength of light and PSII absorbs 680 nm wavelength of light. The overall process of light reaction is completed into the following steps.
- Photoexcitation of Chlorophyll molecules:
- Photolysis Water or Oxidation of water molecules:
- Photophosphorylation:
- Non-cyclic Photophosphorylation:
- Cyclic Photophosphorylation:
