The electron transport
- In photosystem II, the reaction centre chlorophyll a absorbs 680 nm wavelength of red light causing electrons to become excited and jump, which are picked up by an electron acceptor which passes them to an electrons transport system consisting of cytochromes.
- The electrons are passed on to the pigments of photosystem PS I, and the movement of electrons is downhill.
- Electrons in the reaction centre of PS I are also excited when they receive red light of wavelength 700 nm and are transferred to another accepter molecule that has a greater redox potential.
- The electrons then are moved downhill to a molecule of energy-rich NADP+ and the addition of these electrons reduces NADP+ to NADPH + H+.
- The whole scheme of transfer of electrons is called the z-scheme, due to its characteristic shape
Fig. Z scheme of light reaction