(a) The photochemical phase is Hill reaction. It occurs in presence of light. It includes excitation of chlorophyll, photolysis of water molecule, photophosphorylation and reduction of NADP to 15 NADPH2.
(b) The excited chlorophyll transfers an electron from chlorophyll in many steps. Chlorophyll loses an electron from the water molecule in E.T.C. system. Water splits into H+ and OH- ions. Oz is released in it.
4H2O Light > 4H+ + 4OH-Mn++, Cl4OH- ----->2H2O + O2
© The formation of ATP by linking ADP and Pi is called photophosphorylation in photosynthetic E.T.C.
ADP + Pi -----> ATP.
It includes two sets of photochemical reactions catalysed in pigment systems PS-I and PS-II.'NADP is then reduced is NADPH2.