Diffusion

• Diffusion is the spreading of particles of any substance, in solution or a gas, resulting in a net movement from an area of high concentration to an area of low concentration down a concentration gradient.
• The rate of diffusion is affected by the difference in concentration, the temperature and the available surface area.
• Dissolved substances, such as glucose and urea and gases such as oxygen and carbon dioxide move in and out of cells by diffusion.
• Osmosis is the movement of water from a region of high to low concentration through a partially permeable membrane.
• If the concentration of the solutes in the solution outside the cell is higher than the internal concentration, the solution is hypertonic to the cell.
• If the concentration of the solutes in the solution outside the cell is the same as the internal concentration, the solution is isotonic to the cell.
• If the concentration of the solutes in the solution outside the cell is lower than the internal concentration the solution is hypotonic to the cell.