Osmosis

• What is osmosis?

  Diffusion of water across a membrane
• What direction does water move during osmosis?

  From high to low water concentration
• Does osmosis require energy?

  No, it is passive transport
• What type of membrane is involved in osmosis?

  Partially permeable membrane
• How is osmosis defined in terms of solutions?

  Movement from dilute to concentrated solution
• What are the effects of osmosis in different solutions on animal and plant cells?

  • Hypotonic:
  • Animal: Cell swells and may burst (lysis)
  • Plant: Cell becomes turgid
  • Isotonic:
  • Animal: No net movement, cell stays the same
  • Plant: No net movement, cell stays the same
  • Hypertonic:
  • Animal: Cell shrinks (crenation)
  • Plant: Plasmolysis occurs
• What happens to animal cells in a hypotonic solution?

  Cells swell and may burst
• What is the effect of a hypertonic solution on plant cells?

  Water leaves, causing plasmolysis
• What is turgidity in plant cells?

  Cell full of water, firm
• What is flaccidity in plant cells?

  Cell loses water and becomes soft
• What is plasmolysis in plant cells?

  Cell membrane pulls away from the wall
• What factors affect the rate of osmosis?

  • Concentration Gradient: Bigger difference = Faster osmosis
  • Temperature: Higher temperature = Faster movement
  • Surface Area: Larger membrane = More osmosis
  • Water Potential: Higher concentration = More osmosis
• What is the aim of the required practical investigating osmosis in potato cells?

  • Investigate the effect of different sugar concentrations on osmosis in potato cells.
• What equipment is needed for the osmosis practical?

  • Potato cylinders
  • Different sugar solutions
  • Measuring cylinder
  • Balance
  • Petri dishes
• What is the method for investigating osmosis in potato cells?

  1. Cut potato cylinders to the same size.
  2. Measure initial mass.
  3. Place in sugar solutions.
  4. Leave for a set time.
  5. Remove, dry, and re-measure mass.
  6. Calculate percentage change in mass.
• How do you calculate the percentage change in mass?

  % change = (Final mass - Initial mass) / Initial mass × 100
• What happens to potato cells in distilled water?

  Potato gains mass and becomes turgid
• What happens to potato cells in a concentrated sugar solution?

  Potato loses mass and becomes flaccid
• What is the expected result in an isotonic solution for potato cells?

  No significant change in mass
• What are key terms related to osmosis and their definitions?

  • Osmosis: Movement of water from high to low concentration
  • Partially Permeable Membrane: Allows water, not larger molecules
  • Hypotonic: Higher water concentration outside
  • Hypertonic: Higher solute concentration outside
  • Isotonic: Equal water concentration inside and outside
  • Turgid: Plant cell full of water
  • Flaccid: Plant cell loses water
  • Plasmolysis: Membrane pulls away from the wall