Diffusion

• Diffusion


  The spreading out of particles resulting in a net movement from an area of higher concentration to an area of lower concentration
• Molecules that move in and out of cells by diffusion

  • Oxygen
  • Carbon dioxide in gas exchange
  • Urea ( waste product from cells into the blood plasma for secretion in the kidney )
• Cells need oxygen for respiration


  Oxygen moves into the cell by diffusion
• Respiration produces carbon dioxide

  Carbon dioxide moves out of the cell by diffusion
• Urea is a waste product produced inside cells


  Urea diffuses out of the cells into the blood plasma
• Factors affecting the rate of diffusion

  • Difference in concentrations (concentration gradient)
  • Temperature
  • Surface area of the membrane
• Greater concentration gradient


  Faster diffusion
• Higher temperature


  Greater rate of diffusion
• Larger surface area of the cell membrane


  Greater rate of diffusion
• A single-celled organism has a relatively large surface area to volume ratio. This allows sufficient transport of molecules into and

  out of the cell to meet the needs of the organism.