PSII reaction center holds

  > 2 membrane integral proteins
               D1 & D2
  > 2 reaction center chlorophylls
               P680
  > several electron carriers
  > oxygen evolving complex
          on luminal surface made of
              3 extrinsic proteins
                   18kDa, 23kDA, & 33kDa
              & ions
                   4 Mn ions (red)
                   1 Ca ion (blue)
                   1 Cl ion (yellow).
          which splits water (photolysis)

    a tyrosine-161 of D1 conducts
    4 e- from Mn to oxidized P680+
    thereby reducing it.
    oxygen is released as a byproduct