AS LEVEL- Biology- Plasma membranes (2)
- Created by: Ammarah123
- Created on: 02-11-18 16:45
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- 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
- Results
- 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
- The higher the sucrose solution, the higher the water potential
- 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
- Results
- Beetroot- permeability of cell membrane
- 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
- Practicals
- 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
- The higher the sucrose solution, the higher the water potential
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