Osmosis and diffusion DO NOT require energy for materials to enter and exit a cell. How are osmosis and diffusion different from one another? Osmosis is the passive transport of all materials in and out of a cell. Diffusion is the active transport of materials in and out of a cell. While both are passive transport processes, osmosis is the movement of water from low to high concentration of solutes and diffusion is the movement of substances from high to low concentration. Osmosis is the passive transport of water in and out of a cell. Diffusion is the active transport of everything but water in and out of a cell. Both are active transport processes: Osmosis is the movement of water in and out of a cell. Diffusion is the movement of everything but water in and out of a cell​