Photosystem

Photosystem is a protein complex, a key part of the photosynthesis process in plants, algae, and cyanobacteria. It is responsible for the conversion of light energy into chemical energy during photosynthesis. There are two types of photosystems: Photosystem I (PS I) and Photosystem II (PS II), each with a different role in the photosynthetic electron transport chain.

Structure

Photosystems are located in the thylakoid membrane of chloroplasts and are composed of a reaction center surrounded by light-harvesting complexes. These complexes contain chlorophyll molecules, which absorb light energy and transfer it to the reaction center.

Function

The primary function of the photosystem is to capture light energy and convert it into chemical energy. This is achieved through a series of redox reactions, which ultimately lead to the production of ATP and NADPH, two molecules essential for life.

Photosystem I

Photosystem I (PS I) is responsible for providing the electrons needed to reduce NADP+ to NADPH. It does this by absorbing light energy, which excites an electron in the reaction center. This electron is then transferred to a series of electron carriers, ultimately reducing NADP+ to NADPH.

Photosystem II

Photosystem II (PS II) is responsible for the photolysis of water, a process that results in the release of oxygen, protons, and electrons. Like PS I, PS II also absorbs light energy, which excites an electron in the reaction center. This electron is then transferred to a series of electron carriers, ultimately leading to the production of ATP.

See also

• Light-dependent reactions
• Chlorophyll
• Electron transport chain
• Photophosphorylation

Photosystem Resources
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