Phycobiliproteins

Part of speech: noun

Definitions

1. Water-soluble protein pigments found in algae and cyanobacteria that capture light energy for photosynthesis, such as phycocyanin and phycoerythrin
2. Light-absorbing pigment-protein complexes present in red algae, blue-green algae and cyanobacteria that help drive photosynthesis
3. A class of colored proteins, bound to light-sensing chromophores, that algae and cyanobacteria use to gather light for their energy production

Etymology: "Phycobiliproteins" is the plural of "phycobiliprotein", a compound built from three parts: "phyco-", from Greek "phykos" meaning seaweed or algae, "bili-", from Latin "bilis" meaning bile, and "protein". The name is a descriptive coinage, not an ancient term, so the Greek and Latin pieces were assembled deliberately to describe the molecules' structure and colour. The "bili" element refers to the bile pigment chemistry these proteins share. Each one carries a linear tetrapyrrole chromophore, a molecule chemically related to the bilirubin pigment found in animal bile, bound to a protein. Bilins, the family of pigments involved, were named after bile for this reason, which is why an algal light-harvesting protein carries a word from the vocabulary of the gallbladder. The "phyco" element points to the organisms that make these proteins, mainly red algae, cyanobacteria and some cryptophytes. Together with "protein", the name tells you that these are seaweed-associated proteins that bind bile-type pigments, which is exactly what they are.