Plants derive energy from the sun through a process called photosynthesis. At the center of this process is the pigment chlorophyll. Chlorophyll is also found in several one-celled organisms. Algae, diatoms, dinoflagellates, and photosynthetic bacteria all belong to this group of organisms. The chlorophyll in these organisms may be slightly different from that found in multi-celled plants, but the mechanism for deriving energy from sunlight is the same.

The chlorophyll molecule is composed of a central porphyrin ring and side chains. A magnesium atom is found at the center of the porphyrin ring--a complex multi-ring structure composed of carbon, hydrogen, nitrogen, and oxygen atoms. The conjugated double bonds of this structure allow the chlorophyll molecule to absorb energy from sunlight.

There are several types of chlorophylls that all have the central porphyrin ring and magnesium atom in common. The differences are found in their side chains and allow...