Transport In And Out Of Cells Flashcards
Investigating cell membrane permeability – the effect of temperature on beetroot cell membranes:
Use a scalpel to cut five equal sizes of beetroot. Rinse the pieces to remove any pigment released during cutting.
- Add the 5 pieces to 5 different test tubes, each containing 5 cm3 of water.
- Place each test tube of in a water bath at different temperatures for the same length of
time using a stopwatch. - Remove the pieces of beetroot, leaving just the liquid.
- Carry out colorimetry (use the blue filter).
Higher the permeability… (colorimeter)
The higher the permeability, the more pigment released, the higher the
absorbance reading.
Investigating diffusion Concentration:
- Make some agar jelly with phenolphthalein and dilute sodium hydroxide. This will make the jelly pink.
- Prepare 5 test tubes containing HCl in increasing concentrations e.g. 0.2M, 0.4M, 0.6M, 0.8M and 1.0M (synoptic link – serial dilutions).
- Using a scalpel, cut out 5 equal size cubes from the agar jelly.
- Put one of the cubes into the first test tube and use a stopwatch to time how long it
takes for the cube to turn colourless. - Then repeat for the other concentrations, using a new cube each time.
SA
Use a similar method to the concentration method but cut the cubes in different sizes and work out the surface area to volume ratio.
- The smallest cube with the greatest surface area to volume ratio would go colourless fastest.
Temp
- Use a similar method to the surface area method but cut into equal sized cubes.
- Prepare several boiling tubes with the same concentration of HCl.
- Put the boiling tubes in water baths with different temperatures.
- The higher temperatures will make the cubes go colourless faster.
To factors that affect permeability of cell membranes
Temp
Concentration of solvent
Effect of temp
Increase temp - increase membrane permeability
Concentration effect
Increase ethanol concentration = increases membrane permeability = more gaps form
