Light dependent reactions
Plants use water, carbon dioxide and sunlight to produce energy for themselves. The reactions that include sunlight are the light dependent reactions. These include the processes of photosystems 2 and 1 in that order due to the fact that photosystem 1 was discovered first but occurs second in photosynthesis.
Photosystem 2
Photosynthesis begins with photosystem 2. The chloroplast the chlorophyll contains electrons. When a photon of sunlight hits these electron they absorb the energy and become exited. The exited electron is lifted by the chlorophyll and picked up by an electron carrier and transported to another photosystem. The chlorophyll then uses the energy released by this to split a water molecule in half. This releases oxygen into the atmosphere. The picked up electron is then transported through the electron transport chain to the cytocrome complex. This then uses the energy to push ADP and a phospate together into ATP. The cytocrome complex then transports the electron to photosytem 1. This system is on a 680 wavelength.
Photosystem 1
Once electrons are carried by electron carriers to photosytem 1 they lay at the bottom of the system until they are re-energized by more photons, this time photons on a 700 wavelength. this excites the electron again. The exited electron is lifted by the energy and carried by the electron transport system releasing some ATP. This process uses NADP+ reductase to crate a NADHP by pushing NADP and a phosphate group together.