Illustrated Glossary of Organic Chemistry

Chlorophyll: A group of structurally-similar molecules contained in many plants, algae, and cyanobacteria. These molecules are used to harvest light energy (photons) for photosynthesis. Despite their name, chlorophylls do not contain chlorine. Chlorophylls appear green because their HOMO-LUMO gaps are small enough to allow absorption of blue and red light photons.

Molecular structure of chlorophyll a.

Many plants derive their green color from chlorophylls.