tetrapyrrole

A tetrapyrrole is a chemical group composed of four pyrrole rings. These rings can be joined in a straight chain or form a larger ring structure. Pyrrole itself is a heterocyclic organic compound with a ring structure of four carbon atoms and one nitrogen atom.12

Tetrapyrroles are fundamental to many natural pigments. For instance, chlorophylls, the pigments essential for photosynthesis in plants, are magnesium porphyrin compounds where four pyrrole rings form a larger cyclic structure. Similarly, heme, a component of hemoglobin in animals responsible for oxygen transport, also features a porphyrin ring system derived from pyrrole units. Bile pigments, such as bilirubin and biliverdin, are formed from the breakdown of porphyrin rings and consist of a linear chain of four pyrrole rings.3245