Objectives:
-Know how the effect of temperature on membranes can be determined
-Be able to recognise quantitative variables that should be controlled in an investigation
Safety:
-Water baths at temperatures above 50 °C may scald. Take care when removing lids to allow steam to escape away from the face or body.
- Take care with sharp items such as the cork borer and knife
Equipment:
Method:
1. Prepare five water baths pre-set to a range of temperatures 35, 40, 55, 60 and 75 °C.
2. Use a syringe to add 10 cm3 of distilled water to eight test tubes. Label each test tube with a temperature from the pre-set range.
3. Place each tube in the water bath set to the corresponding temperature for 5 minutes.
4. Check the temperature of each bath is correct using a thermometer. It is unlikely to be exactly the desired temperature. Record the actual temperature and use this in your table and graph.
5. Cut five beetroot cylinders using a cork borer. Using a knife, ruler and white tile, trim them all to the same length (1 cm). Wash the cylinders thoroughly with water until the water runs clear and pat dry gently with a paper towel.
6. Add one beetroot cylinder to each of the five tubes and leave in the water bath for 15 minutes.
7. Shake the tubes once. Working quickly, use forceps to remove the cylinders carefully from
each tube. Discard the cylinders, keeping the supernatant liquid. It may be easier to decant the liquid into clean test tubes.
8. Set the colorimeter to a blue/green filter and percentage transmission. Zero the colorimeter using a blank cuvette filled with distilled water.
9. Transfer liquid from each test tube in turn into a colorimeter cuvette, place into the colorimeter and read the percentage transmission reading, recording your results in a suitable table.
10. Plot a graph of transmission against temperature.
Results:
-Know how the effect of temperature on membranes can be determined
-Be able to recognise quantitative variables that should be controlled in an investigation
Safety:
-Water baths at temperatures above 50 °C may scald. Take care when removing lids to allow steam to escape away from the face or body.
- Take care with sharp items such as the cork borer and knife
Equipment:
- Water baths pre-set at required temperatures
- Scalpel
- 10 cm3 syringe
- Thermometer
- Pipette
- Distilled water
- Test tubes
- Syringe
- Colorimeter
- Large beetroot
- Nine cuvettes
- Cork borer size no. 4 or 5
- Labels or pens for labelling
- Ruler
- Forceps
- White tile
Method:
1. Prepare five water baths pre-set to a range of temperatures 35, 40, 55, 60 and 75 °C.
2. Use a syringe to add 10 cm3 of distilled water to eight test tubes. Label each test tube with a temperature from the pre-set range.
3. Place each tube in the water bath set to the corresponding temperature for 5 minutes.
4. Check the temperature of each bath is correct using a thermometer. It is unlikely to be exactly the desired temperature. Record the actual temperature and use this in your table and graph.
5. Cut five beetroot cylinders using a cork borer. Using a knife, ruler and white tile, trim them all to the same length (1 cm). Wash the cylinders thoroughly with water until the water runs clear and pat dry gently with a paper towel.
6. Add one beetroot cylinder to each of the five tubes and leave in the water bath for 15 minutes.
7. Shake the tubes once. Working quickly, use forceps to remove the cylinders carefully from
each tube. Discard the cylinders, keeping the supernatant liquid. It may be easier to decant the liquid into clean test tubes.
8. Set the colorimeter to a blue/green filter and percentage transmission. Zero the colorimeter using a blank cuvette filled with distilled water.
9. Transfer liquid from each test tube in turn into a colorimeter cuvette, place into the colorimeter and read the percentage transmission reading, recording your results in a suitable table.
10. Plot a graph of transmission against temperature.
Results:
Conclusion:
the higher the temperature the beetroot is placed in the more permeable the membranes will become. this is shown in my results by the percentage transmission being 19.5% in the 75°C water meaning that the most liquid leaked from the membrane in the hottest water and so the membranes became the most permeable in the hottest water. this is because in the hotter water the phospholipids in the cell membrane will have more kinetic energy and will be moving faster meaning more liquid can escape.
the higher the temperature the beetroot is placed in the more permeable the membranes will become. this is shown in my results by the percentage transmission being 19.5% in the 75°C water meaning that the most liquid leaked from the membrane in the hottest water and so the membranes became the most permeable in the hottest water. this is because in the hotter water the phospholipids in the cell membrane will have more kinetic energy and will be moving faster meaning more liquid can escape.