Photosynthesis

Abstract

Photosynthesis is the essential biological process that ultimately drives all forms of life. The photosynthetic apparatus of red algae is distinct from that of green algae and plants (green plants) in that phycobilisomes transmit light energy to Photosystem II. There are two types of red algal phycobilisomes, one having phycoerythrins and the other having only phycocyanins, which are similar to those in cyanobacteria. Phycobilisomes also act as a nitrogen reserve. The structure of Photosystem I is essentially similar in red algae and green plants (with some differences in small subunits), whereas the extrinsic proteins of Photosystem II protecting the oxygen-evolving center differ in the two types of photosynthetic organisms. Another major difference is that more components of the two photosystems are encoded by the chloroplast genome in red algae than in green plants, in which most are encoded by the nuclear genome. Cyanidioschyzon merolae serves as a model system for the study of red algal photosynthesis.