"What happens the moment light hits?"
Kana gazed at the chloroplast model.
Rei answered. "Photons are absorbed by chlorophyll."
"And then?"
"Electrons get excited. Jump to a high-energy state."
Toma pointed to the experimental equipment. "Can we measure this?"
Milia nodded. "Fluorescence measurement. When excited electrons return, they emit light."
Kana took notes. "But in photosynthesis, it becomes chemical energy, not light?"
"Yes. Electrons are captured before they return," Rei explained.
"How?"
"Electron transport chain. A series of protein complexes."
Milia drew a diagram. "Photosystem II, cytochrome b6f complex, photosystem I."
Toma asked. "If II is first, why I?"
"Order of discovery," Rei laughed. "Actual electron flow starts with II."
Kana continued. "What happens in photosystem II?"
"Water is split. 2H2O → O2 + 4H+ + 4e-."
"Oxygen comes out!"
"Yes. Most of Earth's oxygen comes from here."
Milia added. "Light energy strips electrons from water."
"Amazing power," Kana murmured.
Rei continued. "Those electrons go through plastoquinone to cytochrome b6f complex."
Toma looked at his notes. "Protons are pumped here?"
"Exactly. Coupled with electron transport, H+ accumulates in the thylakoid lumen."
Kana understood. "A concentration gradient forms?"
"Yes. This drives the next step."
Milia drew the next diagram. "Photosystem I also absorbs light."
"Excited again?"
"Electrons go even higher in energy. Then to ferredoxin."
Rei explained. "Finally NADP+ is reduced to NADPH."
"What's NADPH?" Toma asked.
"Reducing power. Used in the Calvin cycle to fix CO2."
Kana summarized. "Light energy becomes chemical energy through electron excitation."
"Two-stage photochemical reactions," Milia acknowledged.
Rei added. "And the proton gradient drives ATP synthase."
"Drives?" Toma was surprised.
"Literally. F0F1-ATPase is a rotary motor."
Kana was moved. "Molecular machine?"
"Nanomachine. Rotates with proton flow, synthesizing ATP from ADP and phosphate."
Milia showed an animation. "About 100 rotations per second."
Toma calculated. "3 ATP molecules per rotation?"
"Yes. Amazing efficiency."
Kana drew in her notebook. "Light→electron excitation→electron transport→proton gradient→ATP."
Rei summarized. "And NADPH is also obtained. Both needed in Calvin cycle."
"Light energy converts to two forms of chemical energy," Milia said.
Toma asked. "How fast is the moment electrons jump?"
"Femtosecond order. 10 to the minus 15 seconds."
"Too fast..."
"That's why it's efficient. Captured before escaping as heat."
Kana murmured. "The moment photoelectrons jump, life shines."
Rei smiled. "Poetic."
Milia looked at the trees outside. "Even now, countless electrons are jumping."
"Solar energy becomes life energy."
The four fell silent. The dance of light and electrons paints the world green.