PAG 8: Transport In and Out of Cells

Question 1

Investigating cell membrane permeability - the effect of temperature on beetroot cell membranes:

Answer 1

1. Use a scalpel to cut five equal sizes of beetroot. Rinse the pieces to remove any
   pigment released during cutting.
2. Add the 5 pieces to 5 different test tubes, each containing 5 cm3 of water.
3. Place each test tube of in a water bath at different temperatures for the same length of
   time using a stopwatch.
4. Remove the pieces of beetroot, leaving just the liquid.
5. Carry out colorimetry (use the blue filter).
6. The higher the permeability, the more pigment released, the higher the
   absorbance reading.

Question 2

Investigating diffusion - Concentration

Answer 2

1. Make some agar jelly with phenolphthalein and dilute sodium hydroxide. This will
   make the jelly pink.
2. 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).
3. Using a scalpel, cut out 5 equal size cubes from the agar jelly.
4. 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.
5. Then repeat for the other concentrations, using a new cube each time.
6. The highest concentration of HCl will have the fastest colour change as it has the
   steepest concentration gradient.

Question 3

Investigating diffusion - Surface Area

Answer 3

1. Make some agar jelly with phenolphthalein and dilute sodium hydroxide. This will make the jelly pink.
2. Prepare 5 test tubes containing HCl in 0.4 M
3. Using a scalpel, cut out 5 cubes from agar jelly. 0.5 cm^3, 1 cm^3, 1.5 cm^3, 2 cm^3, 2.5 cm^3
4. Put one of the cubes into the first test tube and use stopwatch to time how long it takes for the cube to turn colourless.
5. Repeat for other volumes of cube.
6. The smallest cube with the greatest surface area to volume ratio would go colourless fastest.

Question 4

Investigating diffusion - Temperature

Answer 4

1. Make some agar jelly with phenolphthalein and dilute sodium hydroxide. This will
   make the jelly pink.
2. Prepare 5 test tubes containing 0.2 M HCl.
3. Using a scalpel, cut out 5 equal size cubes from the agar jelly.
4. Put one of the cubes into the first boiling tube and place in 20 degrees Celsius water bath. Use a stopwatch to time how long it
   takes for the cube to turn colourless.
5. Then repeat with water baths of 30, 40, 50 and 60 degrees Celsius
6. The higher temperatures will make the cubes turn colourless faster.