15. Beetroot Core Practical

State the aim for this practical:

Investigating the effect of temperature on membrane permeability

State the hypothesis of this practical:

 Increasing temperature,  increases membrane permeability

State the independent variable in this investigation:

Ethanol concentration

State the factors which should be controlled regarding the beetroot:

AGE & SPECIES OF BEETROOT → Collect samples from the same beetroot

LENGTH & DIAMETER OF BEETROOT →

- Use a cork borer to cut samples with same diameter
- Use a ruler to measure pieces of the same length

What other variables should be controlled?

1. Temperature → Place samples in a water bath set at the same temperature

2. Volume of ethanol

3. Volume of solution in the cuvette

Suggest a suitable control experiment:

Beetroot discs in distilled water or 0% ethanol

Describe how quantitative data is collected in this practical and state the benefits of having quantitative data:

Colorimeter so statistical tests can be done

→ Removes bias

What is the independent variable?

Temperature by using water baths

What is the dependent variable?

Permeability of the membrane by using a colorimeter (absorbance)

What could you do to ensure the results are concordant?

Repeat each temperature 5 times and calculate an average

Beetroot Core Practical Method:

1. Cut cylindrical samples from a single beetroot using a size 4 cork borer.
   Cut eight 1 cm length sections from these samples.

2. Place eight labelled boiling tubes, each containing 5 cm³ distilled water, into water baths at 20^oC, 30^oC, 40^oC, 50^oC, 60^oC and 70^oC.

3. Leave for 5 minutes until the water reaches the required temperature.
   Place one of the beetroot sections into each of the boiling tubes.
   Leave for 20 minutes in the water baths.

4. Decant the liquid into a second boiling tube
   Shake the water/solution to disperse the dye.

5. Switch on the colorimeter and set it to read percentage absorbance.

6. Using a pipette, accurately measure 2 cm water into a cuvette.

7. Place the cuvette into the colorimeter.

8. Calibrate the colorimeter to read 0 absorbance for clear water.

9. Place 2 cm³ of the dye solution into a colorimeter cuvette and take a reading for absorbency.

10. Repeat the readings for all the temperatures