Bile pigments exist in both the animal and plant kingdoms, and are building by breakdown of the cyclic tetrapyrrole structure of heme. In the animals this pathway is an excretory system by that the heme from the hemoglobin of aging red blood cells, and other hemoproteins, is deleted from the body. In the plant kingdom, moreover, heme is broken down to form bile pigments that have major roles to play in coordinating light responses in higher plants (the phycobiliprotein phytochrome), and in light harvesting in algae (the phycobiliproteins phycoerythrin and phycocyanin).