what is the difference between C3 and C4 pathway ?
C3 - Fixes carbon from C02 into a 3 carbon sugar (3-phospoglycerate)
C3 plants require less ATP for carbon fixation. Both proccesses were evolutionary devices to allow plants to live in different environments.
C4 - Fixes carbon from CO2 into a 4 carbon sugar,
C4 plants live in adverse environments, eg in the desert.