Gas exchange happens in the spongy mesophyll tissue of the leaf. Spongy mesophyll cells are covered by a thin layer of water and loosely packed. When the plant is photosynthesising during the day, these features allow carbon dioxide to diffuse into the spongy mesophyll cells, and oxygen to diffuse out of it.
If one organ doesnt work ex. kidney it can work without the other one. if the liver how ever fails, it doesnt have another one and would need to have a transplant in order to stay alive.
