Photosystem II (PSII)

Definition

Photosystem II (PSII) is a protein complex in the thylakoid membrane of chloroplasts involved in the light-dependent reactions of photosynthesis. It uses light energy to extract electrons from water, generating oxygen and protons.

5 Must Know Facts For Your Next Test

1. PSII is the first protein complex in the light-dependent reactions of photosynthesis.
2. It captures photons and uses the energy to extract electrons from water molecules.
3. The splitting of water by PSII releases oxygen as a byproduct.
4. Electrons from PSII are passed to plastoquinone, starting an electron transport chain.
5. PSII contributes to the creation of a proton gradient used for ATP synthesis.

Related terms

Photosystem I (PSI): A protein complex that works after PSII in photosynthesis and helps produce NADPH.

Plastoquinone: An electron carrier that transports electrons from PSII to cytochrome b6f complex.

Thylakoid Membrane: The site within chloroplasts where PSII and other components of the light-dependent reactions are located.