Photosynthetic Electron Transport Chain

1. Components: The photosynthetic electron transport chain includes Photosystem II, the cytochrome b6f complex, Photosystem I, and several other electron carriers.

2. Function: Its main function is to transfer electrons from water to NADP+, creating a flow of protons across the thylakoid membrane, which drives the synthesis of ATP.

3. Process:

• Photosystem II (PSII): It absorbs light, which excites electrons to a higher energy state. These electrons are then passed to the electron transport chain. PSII also splits water molecules to replace the lost electrons, releasing oxygen as a by-product.

• Cytochrome b6f complex: This complex facilitates the transfer of electrons between PSII and PSI. The energy released during electron transfer is used to pump protons into the thylakoid lumen, creating a proton gradient.

• Photosystem I (PSI): It receives electrons from the cytochrome b6f complex. PSI also absorbs light, further boosting the energy level of electrons. These high-energy electrons are then used to reduce NADP+ to NADPH.

• ATP Synthesis: The proton gradient across the thylakoid membrane drives ATP synthase to produce ATP from ADP and inorganic phosphate.