Which complex is responsible for splitting water to release oxygen in photosynthesis?

Which complex is responsible for splitting water to release oxygen in photosynthesis?

• A. Oxygen-evolving complex in PSII.
• B. NADP+ reductase in the stroma.
• C. Ferredoxin in the stroma.
• D. Cytochrome b6f complex in the thylakoid lumen.

Answer: (A)

The splitting of water to release oxygen happens at the oxygen-evolving complex associated with photosystem II. This specialized part of PSII contains a Mn4CaO5 cluster that uses light energy to pull electrons from water molecules. As water is oxidized, oxygen gas is produced and released into the surrounding lumen, while protons are released into the lumen and electrons are handed off to the photosystem II electron transport chain to continue the flow of energy. This is distinct from the other components: NADP+ reductase on the stromal side uses electrons to reduce NADP+ to NADPH; ferredoxin serves as the immediate electron donor to NADP+ reductase; and the cytochrome b6f complex passes electrons between PSII and PSI while pumping protons, but it does not split water.

The splitting of water to release oxygen happens at the oxygen-evolving complex associated with photosystem II. This specialized part of PSII contains a Mn4CaO5 cluster that uses light energy to pull electrons from water molecules. As water is oxidized, oxygen gas is produced and released into the surrounding lumen, while protons are released into the lumen and electrons are handed off to the photosystem II electron transport chain to continue the flow of energy.

This is distinct from the other components: NADP+ reductase on the stromal side uses electrons to reduce NADP+ to NADPH; ferredoxin serves as the immediate electron donor to NADP+ reductase; and the cytochrome b6f complex passes electrons between PSII and PSI while pumping protons, but it does not split water.