Diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration. It takes place along the concentration gradient. There are two types of diffusion i.e. simple diffusion and facilitated diffusion. It helps in the exchange of gases such as carbon dioxide, oxygen and water between the stomata and the atmosphere. It also helps in exchange of gases in the alveoli of lungs during respiration.

Osmosis is the process by which solvent molecules move from a region of lower concentration to a region of higher concentration through a semipermeable membrane. There are two types of osmosis i.e. endosmosis and exosmosis. Osmosis helps in transportation of nutrients and excretion of metabolic wastes. It also helps in maintaining turgidity of the cell.