ABSTRACT
Photosynthetic organisms contain some form of the light-absorbing pigment chlorophyll (Chl). Photosynthetic organisms that perform oxygenic photosynthesis, such as cyanobacteria, algae, and plants, synthesize Chl a. A group of cyanobacteria (prochlorophytes), green algae, and plants also contain Chl b. Photosynthetic bacteria, which perform anaerobic photosynthesis, produce a variety of derivatives called bacteriochlorophylls (Bchls). In the order of their discovery, Chls and Bchls are named a–f and a–g, respectively. Chls contain a tetrapyrrole ring structure like that found in heme (Figure 9.1). However, Chls bind an Mg atom in the center of its ring structure, while hemes bind an Fe atom. In addition, a hydrophobic phytol chain is attached to the ring structure of Chl that makes the molecule extremely nonpolar. All Chls are noncovalently bound to various photosystem subunits in the thylakoid membrane.
