Which essential inorganic ions are required as catalytic cofactors for the photolysis of water in Photosystem II?
Answer and explanation
Correct answer: B. Manganese and Chloride
- Step 1: The water-oxidizing complex of Photosystem II requires specific mineral ions to cycle through multiple oxidation states ( to ).
- Step 2: Four manganese () atoms form the catalytic cubane core alongside calcium ().
- Step 3: Chloride () ions act as essential counter-anions facilitating proton-coupled electron transfers during the release of .
Answer
Manganese () and Chloride ()
Why not the others: 'Magnesium () and Iron ()' are structural components of the porphyrin ring of chlorophyll and cytochrome/ferredoxin centers, respectively; 'Zinc () and Copper ()' function in carbonic anhydrase and plastocyanin, respectively; 'Molybdenum () and Boron ()' are involved in nitrate reductase and pollen germination/carbohydrate translocation.
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