Here's how it works:
1. Light Absorption: Light energy is absorbed by chlorophyll molecules within PSII.
2. Excitation: This absorbed light energy excites electrons within the chlorophyll molecules, boosting them to a higher energy level.
3. Water Splitting: The excited electrons are then transferred to a special molecule called the "reaction center" of PSII. To replace these lost electrons, PSII uses light energy to split water molecules into:
* Oxygen (O2): This is released as a byproduct of photosynthesis.
* Hydrogen ions (H+): These contribute to the proton gradient used for ATP synthesis.
* Electrons: These electrons are the ones that replace the excited electrons that were initially lost from chlorophyll.
Therefore, the excited electrons flowing through PSII ultimately originate from water molecules.
