Diffusion and Osmosis

• Diffusion


  Movement of molecules from high to low concentration.
• Osmosis


  Movement of water from a high to low water concentration through a partially permeable membrane.
• Osmosis in animal cells 


  • In a strong solution: cell loses water and shrinks (crenated).
  • In distilled water: cell gains water, may burst due to lack of cell wall.
• osmosis in plant cells


  • In a strong solution: cell loses water, becomes flaccid.
  • In distilled water: cell gains water, becomes turgid; turgor provides structure
• Active Transport


  Movement of particles from low to high concentration using energy.
• Factors Affecting Movement of Substances

  • Surface Area to Volume Ratio: Higher SAratio increases rate.
  • Diffusion Distance: Shorter distances increase rate.
  • Temperature: Higher temperatures increase particle energy and movement.
  • Concentration Gradient: Greater differences in concentration increase rate.
• Practical: Investigating Diffusion


  Use beetroot cells; heat impacts cell membrane, allowing pigment leakage, indicating diffusion rate.

  • More pigment leakage at higher temperatures due to increased kinetic energy.
• Practical: Investigating Osmosis with Potato Cylinders


  • Method: Place potato cylinders in various sucrose solutions, measure mass changes.
  • Results:
  • Potato gains mass in distilled water (high water concentration).
  • Potato loses mass in strong sucrose (low water concentration).
  • No mass change if solution is isotonic with potato cells.
• Key Evaluation (CORMS)


  a

  • C - Change the variable (e.g., temperature or sucrose concentration).
  • O - Use the same source for biological material (e.g., same beetroot or potato).
  • R - Repeat experiments for reliability.
  • M1 - Measure the outcome (e.g., color intensity or mass change).
  • M2 - Measure at a consistent time point (e.g., 10 minutes, 4 hours).
  • S - Standardize conditions (e.g., volume of water, surface area).