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A Photosystem Is a Pigment Array Plus a Reaction Centre
A photosystem is a pigment-protein complex that absorbs light and excites electrons.
In eukaryotes such as plants and algae, photosystems sit in the thylakoid membranes of chloroplasts.
In cyanobacteria, they sit in the plasma membrane or internal thylakoid membranes.
Analogy
- A photosystem works like a solar panel.
- A panel captures sunlight and turns it into electricity.
- A photosystem absorbs light and turns it into an excited electron.
Two Parts Make Up Every Photosystem
Antenna complex (light-harvesting complex)
- It holds hundreds of chlorophyll molecules and accessory pigments such as carotenoids.
- These pigments absorb photons and pass the energy inward toward the reaction centre.
Reaction centre
