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
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