IGCSE Biology 0610

3.1 Diffusion

• Diffusion is the net movement of particles from a region of their higher concentration to a region of their lower concentration (down a concentration gradient), as a result of their random movement
• The energy for diffusion comes from the kinetic energy of random movement of molecules and ions
• Some substances move into and out of cells by diffusion through the cell membrane

Importance of Diffusion of Gases & Solutes in Living Organisms

• Gas exchange for respiration
• Obtain requirements
• Get rid of waste materials

Factors that Affect Diffusion

• Surface area – Folded cell membrane = larger surface = allows more molecules to diffuse
• Temperature – Diffusion is faster at warmer temperatures
• Concentration gradient – Cells use substances that diffuse quickly so low concentration in cytoplasm keeps a steep concentration gradient
• Distance – Cell membranes are thin so molecules travel less distance