Photosystem I (PSI)

Definition

Photosystem I (PSI) is a protein complex in the thylakoid membrane that plays a crucial role in the light-dependent reactions of photosynthesis. It is responsible for the final stage of electron transport, ultimately producing NADPH.

5 Must Know Facts For Your Next Test

1. PSI operates best at a wavelength of 700 nm, often referred to as P700.
2. It works in tandem with Photosystem II (PSII) but functions later in the electron transport chain.
3. The primary function of PSI is to facilitate the transfer of electrons from plastocyanin to ferredoxin.
4. NADP+ reductase, associated with PSI, reduces NADP+ to NADPH using electrons provided by PSI.
5. PSI contains chlorophyll molecules that capture light energy and drive the electron transport process.

Review Questions

• What is the primary function of Photosystem I in photosynthesis?
• At what wavelength does Photosystem I operate most efficiently?
• Which molecule does Photosystem I ultimately reduce to form NADPH?

Related terms

Photosystem II (PSII): A protein complex that initiates the light-dependent reactions by capturing photons and splitting water molecules.

Electron Transport Chain: A series of protein complexes that transfer electrons through a membrane to create a proton gradient for ATP synthesis.

NADP+ Reductase: An enzyme associated with PSI that catalyzes the reduction of NADP+ to NADPH.