What is diffusion?

• diffusion is the spreading out of the particles of any substance in solution, or particles of a gas, resulting in a net movement from an area of higher concentration to an area of lower concentration
• in cells, diffusion happens across the cell membranes, to allow substances such as oxygen and carbon dioxide to get in and out of cell
• Diffusion also allows the waste product, urea, to get out of the cell
• diffusion is a passive process because it does not require any energy
• the diagram below shows the movement of particles across the cell membrane over time. The particles move from the more concentrated side to the less concentrated side, until both sides have the same number of particles (equilibrium).