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.

• 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. Understand that the light reactions of photosynthesis occur in the thylakoid membranes of chloroplasts and involve the conversion of light energy into chemical energy.
2. Recognize that Photosystem II (PSII) is the first step in the light reactions, where light energy is absorbed and used to split water molecules, releasing oxygen and electrons.
3. The electrons released from Photosystem II are then passed through an Electron Transport Chain (ETC), which helps in creating a proton gradient across the thylakoid membrane.
4. Next, the electrons reach Photosystem I (PSI), where they are re-energized by light absorption and then used to reduce NADP+ to NADPH.
5. Finally, the proton gradient created by the ETC is used to drive ATP synthesis through chemiosmosis, completing the light reactions of photosynthesis.