What are clusters of pigment molecules?

Clusters of pigment molecules are called photosystems. They are located in the thylakoid membrane of chloroplasts, and include chlorophyll a, chlorophyll b and carotenoids. Photosystems absorb light energy to use in photosynthesis.

The chlorophylls are green because they absorb all wavelengths of light except green. The carotenoids are yellow, orange and red because they absorb all wavelengths of light except yellow, orange and red. Together, they efficiently absorb energy from sunlight.

The energy absorbed first splits water into hydrogen and oxygen. The oxygen is a waste product while the hydrogen continues in the process. A second photosystem uses these hydrogen atoms and absorbed light energy to create ATP and NADPH. The ATP and NADPH molecules are needed in the Calvin cycle to make sugar.