The water coupling/dioxygen evolving reactionpromoted by photosynthetic organisms (involves the proton-coupled four electron oxidation of twowater molecules along with O-O bond formationto yield dioxygen (O2). This is the dominantglobal process responsible for replenishingatmospheric oxygen essential for life.
a. What would the redox potential of the photosynthetic reaction site have to be in order todrive this reaction under physiological conditions (iepH= 7)?
b. Would you want to raise or lower the pH inorder to make this reaction more favorable? Explain.
c. The catalytic site that promotes thisreaction (O2 formation from H2O) consists of a cluster of four Mn ions, in a mixture of +3, +4, and possibly +5 oxidation states. Can you think of a reason why nature would devise such a complex system, when according to standard potential table,MnO4- would capable of promoting this reaction?