my questions are the following. If we agree that PEP carboxylase is more efficient than RuBisCO since it can't bind Oxygen, why isn't it present in C3 plants as well? Is it just a question of evolution and C3 plants are just "worse" with regards to efficiency, or is there any usefulness in having an enzyme like RuBisCO instead? (RuBisCO is present in C4 plants as well, right?)
Second question: PEP carboxylase doesn't bind Oxygen. In C4 plants, we have bundle sheeth cells that don't have grana. Why isn't it a good idea to let the Calvin cycle unfold in "normal" cells that have grana, if PEP carboxylase doesn't bind Oxygen anyway? Why are we better of with the Calvin cycle happening in the bundle sheeth cells for a good part? Or is RuBisCO still used even in C4 plants? I'd be grateful for any help, sorry if some english term is not correct.