Diffusion

• Substances may move into and out of cells across the cell membranes via 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
• Some of the substances transported in and out of cells by diffusion are oxygen and carbon dioxide in gas exchange, and of the waste product urea from cells into the blood plasma for excretion in the kidney
• As the difference in concentrations (concentration gradient) increases the rate of diffusion increases
• A higher temperature will increase the rate of diffusion because the particles have more kinetic energy to move around faster
• The larger the surface area of the membrane the faster the rate of diffusion because more particles can pass through at once