AS LEVEL- Biology- Plasma membranes (2)

View mindmap
  • Plasma membranes (2)
    • Practicals
      • Beetroot- permeability of cell membrane
        • Results
          • The higher the permeability of the membrane, the more pigment is released , so the higher the absorbance of the liquid
          • The higher the temp, the lower the % transmission of light
            • 1) This is because there are more gaps in the membrane so the phospholipids are moving around more
            • 2) If there are more gaps in the membrane, it increases the permeability of the membrane
            • 3) Betalains can diffuse out- Surrounding solution has a darker colour
      • Agar jelly- investigating diffusion in model cells
      • Potato- investigating water potential
        • Results
          • The higher the sucrose solution, the higher the water potential
            • A high concentration of sucrose solution will have a low water potential so water will move out of the potato cell
            • A low concentration of sucrose solution will have a high water potential so water will move into the potato cell
        • Procedure
          • 1) Prepare sucrose solutions of different concentrations
          • 4) Place one group in each solution
          • 5) Leave the chips in the solution for 20 mins making sure they all get the same amount of time
          • 8) Calculate the % change in mass+ plot your results on a graph
          • 7) Weigh each group again + record your results
          • 6) Remove the chips + pat gently with a paper towel to remove excess water as the excess water would affect the final mass
    • Diffusion (Passive- No energy is required)
      • Passive-Energy for movement comes from the natural/kinetic energy of molecules
      • Diffusion- Overall movement of particles from a region of high to low concentration
      • Particles diffuse down a concentration gradient
      • 1) Small non- polar molecules eg. oxygen + carbon dioxide are able to diffuse easily through spaces between phospholipids
      • 2) Water is also small enough to fit between the phospholipids, so its able to diffuse across plasma membranes even though it's polar
      • Factors that affect the rate of diffusion
        • Concentration gradient- Higher the concentration gradient = faster rate of diffusion
        • Thickness of exchange surface- Thinner the exchange surface = faster rate of diffusion
        • SA- Larger SA = faster rate of diffusion
        • Temp- Warmer it is = faster rate of diffusion as participles have more kinetic energy so they move faster
  • Results
    • The higher the sucrose solution, the higher the water potential
      • A high concentration of sucrose solution will have a low water potential so water will move out of the potato cell
      • A low concentration of sucrose solution will have a high water potential so water will move into the potato cell

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Biological membranes resources »