All the reactions of photosynthesis that are directly dependent upon light are known as the light reactions. The light reactions occur in the part of the cell known as the thylakoids (Stacks of thylakoids are known as grana.). Many chlorophyll molecules are found embedded into the membranes of the thylakoids.
The purpose of the light reactions is to convert light energy into chemical energy in the form of ATP & NADPH.
ATP & NADPH are energy carriers. They carry energy to the 2nd part of photosynthesis, known as the dark reactions.
The light reactions can be split into the following specific steps:
1. Light absorption & splitting of water.
2. Production of ATP.
3. Movement of electrons through electron acceptors to power a hydrogen pump.
4. Re-energizing electrons so they can produce NADPH.