The pathway crosses several cells, one in which CO2 is filtered from an oxygen atmosphere and another anoxic stage where the CO2 is fixed again, this time to pr

The pathway crosses several cells, one in which CO2 is filtered from an oxygen atmosphere and another anoxic stage where the CO2 is fixed again, this time to produce sugars which plants actually need. The two stage fixation prevents something called 'photorespiration' where existing oxygen can 'steal' some of the rubisco mollecules which would otherwise associate with CO2. So this is a multicellular process and could not be adapted to algae.