Photosynthesis occurs in 3 main stages: energy is captured from sunlight, thenits converted into chemical energy and stored in organic molecules.
Photosystems are light harvesting units of the thylakoid membrane. Eachphotosystem has four hundred pigment molecules. A photon hits the pigmentmolecules and travels through each molecule and then reaches the reaction centeras shown in figure 1-1. The thylakoid membrane has two photosystems, photosystem1 & 2. The reaction center in photosystem 1 is called P700 because thispigment is best at absorbing 700 mm light. Photosystem 2s reaction center iscalled P680 because it is best at absorbing 680 mm light.
Calvin Cycle TheCalvin cycle begins by incorporating Co2 from the air into molecules in thechloroplast. This action is called carbon fixation. The next thing it does isadd electrons to the fixed carbon to make it carbohydrate. The power of theCalvin cycle comes from NADPH. The Calvin cycle also needs energy from ATP,which is generated by light reactions. This is reaction is called darkreactions because it does not directly need light to work.
So basically allthe Calvin cycle does is make sugar with out light but with help from ATP &NADPH.