Photosystem

Definition

A photosystem is a protein complex in chloroplasts and cyanobacteria that absorbs light during photosynthesis, initiating the conversion of light energy into chemical energy. It consists of a reaction center surrounded by light-harvesting complexes.

5 Must Know Facts For Your Next Test

1. Photosystems are integral components of the thylakoid membranes in chloroplasts.
2. There are two main types: Photosystem I (PSI) and Photosystem II (PSII), each playing distinct roles in the light reactions of photosynthesis.
3. Photosystem II captures photons to split water molecules, releasing oxygen and generating electrons.
4. Photosystem I uses light energy to produce NADPH from NADP+ and H+.
5. The efficiency of photosystems is critical for the overall productivity of photosynthesis.

Review Questions

• What are the primary functions of Photosystem I and Photosystem II?
• How do photosystems contribute to the production of ATP and NADPH?
• Where within the cell are photosystems located?

Related terms

Thylakoid Membrane: The internal membrane system in chloroplasts where photosynthesis occurs.

Chlorophyll:

A pigment molecule that absorbs light energy for use in photosynthesis.

Electron Transport Chain:

A series of protein complexes that transfer electrons during the light-dependent reactions of photosynthesis.