Why does the process of diffusion occur?
Well lets get the distinction of diffusion and osmosis clear: Diffusion is the passive movement of particles from a region of higher concentration to a region of lower concentration, as a result of the random motion of particles. Osmosis is the passive movement of water molecules across a partially permeable membrane from a region of lower solute concentration to a region of higher solute concentration. When the cell needs to create an equal solute concentration, passive transport across a biological membrane work comes in play: The partially permeable nature of membranes of cells allows some material to move across the membrane while others cannot. So in a situation with a partially permeable membrane solutes (Na+, Ca2+, etc.) are impermeable. The movement of water particles helps create a balance between the extra cellular fluid, and the inside of the cell. An example could be when there is a high solute concentration in the cell, and a low solute concentration in the extra cellular
