Which set of products results from the photolysis of water during photosynthesis?

• A. Hydrogen (Proton), Oxygen and High-Energy Electron
• B. Hydrogen Only
• C. Oxygen Only
• D. Glucose

Answer: (A)

Water is split in the light-dependent reactions by the oxygen-evolving complex of photosystem II. This photolysis yields three things: protons (hydrogen ions), high-energy electrons, and molecular oxygen. The balanced form is 2 H2O → 4 H+ + 4 e− + O2. The released electrons feed the electron transport chain, helping to create the proton gradient that drives ATP formation and eventually the production of NADPH, while the oxygen gas is released as a byproduct. So the products are hydrogen ions, oxygen, and high-energy electrons. Glucose isn’t produced in this step; it comes later in the Calvin cycle using ATP and NADPH from these reactions.