What is the correct order of steps of the light reactions of Photosynthesis?

• A. photosystem I, ETC, photosystem II, NADP⁺ reduction, chemiosmosis.
• B. photosystem I, photosystem II, ETC, NADP⁺ reduction, chemiosmosis.
• C. photosystem II, ETC, photosystem I, NADP⁺ reduction, chemiosmosis.
• D. photosystem II, photosystem I, ETC, NADP⁺ reduction, chemiosmosis.

Answer: (C)

Verified step by step guidance

1. Begin with Photosystem II, where light energy is absorbed by chlorophyll, exciting electrons to a higher energy level.
2. These high-energy electrons are then transferred to the Electron Transport Chain (ETC), where they move through a series of proteins, releasing energy used to pump protons across the thylakoid membrane.
3. Next, the electrons reach Photosystem I, where they are re-energized by another photon of light absorbed by chlorophyll.
4. The re-energized electrons are used to reduce NADP+ to NADPH, a crucial molecule for the Calvin cycle.
5. Finally, the proton gradient created by the ETC drives chemiosmosis, where ATP is synthesized from ADP and inorganic phosphate via ATP synthase.