Non cyclic phosphorylation

• 1. When a photon of luight strikes the second photosystem, energy is channeled in the primary pigment reaction centre
• 2. the light eneregfy excites a pair of electrons inside of the chlorophyll molecule
• 3. the energised electrons escape from the chlorophyll molecules, they are captured by electron carriers. Electron carriers are proteins that have an iron ion in its centre, embedded in the thylakoid membrane
• 4. the electrons that are captrued by thre electron carrier replace the electrons lost in photolysis
• 5. when the iron ion of the electron carrier combines with an electron, it is reduced to 2+. It will donate an electron, oxidising to 3+, to the next carrier in the ETC
• 6. As electrons are passed along the electron transport chain that is embedded in the thylakoid membrane, energy is released per step of the ETC.
• 7. The energy released as an electron moves down the ETC is used to pump protons across the membrane into the thylakoid spacer actively.
• 8. Eventually, the electrons are captured by another molecule of chlorophyll A in photosystem one. These electrons replace the electrons lost in photosystem one because of light energy.
• 9. A molecule of ferredoxin accepts the eelctrons from photosystem one, passing them to NADP in the Stroma
• 10. as protons accumulate in the thylakoid space, a proton gradient forms across the membrane
• 11. Protons diffuse down the concentration gradient via ATP synthase molecules. This causes Adeno DI phosphate and inorganic phosphate groups to bond to form ATP.
• 12. as the protons pass through ATP synthase channels, they are accepted, along with electrons, by NADP which becomes reduced. The reduction of NADP is catalysed by NADP reductase
• The light energy has been converted into chemical energy in the form of ATP by photophosphorylation
• ATP and reduced NADP are now in the stroma, ready for use in the light independent stage.