C3 plants fix carbon dioxide through rubisco; however, oxygen competes for rubisco binding, reducing the ability for C3 plants to fix carbon. C4 plants use phosphoenolpyruvate (PEP) carboxylase instead of rubisco, which binds carbon dioxide specifically.

C3 plants are more suitable than C4 plants for growth in arid climates because they keep their stroma closed longer than C4 plants.

C3 plants have fewer photosystems than C4 plants; as a result, C4 plants are able to utlize a broader spectra of light in the light reactions of photosynthesis.

C3 plants physically separate carbon fixation and the Calvin cycle, whereas C4 plants execute both processes in the chloroplast stroma.

The calvin cycle in C4 plants does not require NADPH; therefore, the light reactions are more efficient because they do not have to regenerate NADPH from NADP+

Ribulose-1,5-bisphosphate

Glyceraldehyde-3-phosphate

1,3-bisphosphoglycerate

Glucose-6-phosphate

fix . . . C3

oxidize . . . C2

oxidize . . . C3

fix . . . C2

phosphorylate . . . C3