Monai Elnaasani
Describe how membrane structure can be investigated practically, e.g. by the
effect of alcohol concentration or temperature on membrane permeability.
Past paper - June 2009, January 2014, January 2018
Alcohol
1. Cut out beetroot cylinders from a beetroot
2. Cut them into discs 10mm using a blade
3. Rinse them down in distilled water, dab in a dry cloth
4. Prepare alcohol solutions of concentrations 0-50%
5. Place 5cm3 preach solution in 5 test tubes at the same temperature in a water
bath, leave for 20 minutes
6. Calibrate a colorimeter by placing distiller water
7. Measure the absorbance of the blank
8. Measure the absorbance of solution form each test tube
9. Repeat the experiment for each concentration of alcohol and calculate the average
absorbance
Independent variable;
• Concentration of alcohol
Dependent variable;
• % absorbance of light through resulting solution
Temperature
1. Cut out beetroot cylinders from a beetroot
2. Cut the cylinders into pieces of 10mm thickness rinse the discs in distilled water till
color doesn’t come out
3. Dab them with dry cloth
4. Place 5cm3 of water in five test tubes and keep them at 0ºC-40ºC for 30 mins
5. Calibrate a colorimeter, place water in a clean cuvette
6. Note the blank reading place the solution form different test tubes in the
cuvette on at a time, choose the right filter
7. Note the absorbance
8. Repeat the experiment, calculate the mean absorbance
Independent variable;
• Temperature of water
Dependent variable;
• % absorbance of light through solution
Controlled variable;
• Species of beet root from same plant
• Age of beetroot
• Rinse beetroot until its clear
• Surface area of disc
• Use same part of the beetroot, cut from the middle
• Filter used
Pearson Edexcel Advanced Level Biology Unit 3 - notes for success
Describe how membrane structure can be investigated practically, e.g. by the
effect of alcohol concentration or temperature on membrane permeability.
Past paper - June 2009, January 2014, January 2018
Alcohol
1. Cut out beetroot cylinders from a beetroot
2. Cut them into discs 10mm using a blade
3. Rinse them down in distilled water, dab in a dry cloth
4. Prepare alcohol solutions of concentrations 0-50%
5. Place 5cm3 preach solution in 5 test tubes at the same temperature in a water
bath, leave for 20 minutes
6. Calibrate a colorimeter by placing distiller water
7. Measure the absorbance of the blank
8. Measure the absorbance of solution form each test tube
9. Repeat the experiment for each concentration of alcohol and calculate the average
absorbance
Independent variable;
• Concentration of alcohol
Dependent variable;
• % absorbance of light through resulting solution
Temperature
1. Cut out beetroot cylinders from a beetroot
2. Cut the cylinders into pieces of 10mm thickness rinse the discs in distilled water till
color doesn’t come out
3. Dab them with dry cloth
4. Place 5cm3 of water in five test tubes and keep them at 0ºC-40ºC for 30 mins
5. Calibrate a colorimeter, place water in a clean cuvette
6. Note the blank reading place the solution form different test tubes in the
cuvette on at a time, choose the right filter
7. Note the absorbance
8. Repeat the experiment, calculate the mean absorbance
Independent variable;
• Temperature of water
Dependent variable;
• % absorbance of light through solution
Controlled variable;
• Species of beet root from same plant
• Age of beetroot
• Rinse beetroot until its clear
• Surface area of disc
• Use same part of the beetroot, cut from the middle
• Filter used
Pearson Edexcel Advanced Level Biology Unit 3 - notes for success
