Photosynthesis-The Light Reactions

<PSI & PSII Electron Transport Chain>

• Reduction is the gaining of electrons and oxidization is the losing of electrons. Photosynthesis is processed through transfer of electrons.
• PSII is first stimulated by sunlight to obtain electrons from water. The hydrogen bond breaks and two H+ bond together and form hydrogen gas.This process of breaking hydrogen bond through sunlight is called photolysis.
• The electrons are then passed from PSII to PQ. Therefore, PSII is oxidized and PQ is reduced.
• Since PQ is a proton carrier, a bridge forms inside PQ allowing hydrogen to come in.
• The electrons are passed from PQ to b6f. Therefore, PQ is oxidized and b6f is reduced.
• PSI is stimulated by sunlight to obtain electrons from b6f. Therefore, b6f is oxidized and PSI is reduced.
• The electrons are passed from PSI to Fd. Therefore, PSI is oxidized and Fd is reduced.
• The electrons are passed from Fd to FNR. Therefore, Fd is oxidized and FNR is reduced.
• The electrons are passed from FNR to NADP. Therefore FNR is oxidized and NADP is reduced.
• A hydrogen then bonds to NADP and results in NADPH.
• However, after the gaining of hydrogen, the environment becomes too acidic so it is then turned to neutral by a process known as chemiosmosis.
• The hydrogen is allowed out of the system by chemiosmosis where hydrogen moves from a high to low concentration through a semi-permeable membrane.
• A phosphate is joined to ADP through ATP synthase and becomes ATP and hydrogen leaves the system.