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).