noun, plural: phycobilisomes
A phycobilisome is a light-harvesting antenna of cyanobacteria, red algae, and glaucophytes. It is an enormous light harvesting complex (~3 - 7 MDa molecular weight, with dimensions 40 nm – 60 nm) found at the stromal side of the thylakoid membrane. It serves as an initial site of photosynthesis since it absorbs light energy and then pass it to the photosynthetic reaction centers, often to Photosystem II.1 It is comprised of phycobiliproteins (proteins with phycobilin pigments) covalently bound to linker proteins.
Phycobilisomes are essential in a way that they can absorb wavelengths of light at 500 to 650 nm in which the chlorophyll is unable to. The light energy absorbed by the phycobilisomes within that range is transferred to the chlorophyll a of the photosystem II. Having phycobilisomes proves advantageous to photosynthetic organisms that thrive deeper in the water column and where light with longer wavelengths is less transmitted. Phycobilisomes enable 95% efficiency of energy transfer.2
1 David, L. & Adir, N. Isolation of Intact Phycobilisomes in Low Salt: a Novel Method for Purifying Phycobilisomes by Mild Cross-Linking. Photosynthesis Research for Food, Fuel and the Future Part of the series Advanced Topics in Science and Technology in China. pp 143-147.
2 Phycobilisomes. Retrieved from [].