Beetroot membrane

Risk assessment:

• Taking care when using the cork borer and knife when dividing the beetroot sections.
• Boiling tubes should be handled with care, especially in the water baths.

Apparatus:

• One beetroot
• One size 4 cork borer
• White tile
• Knife
• Ruler
• Water Baths at 0 oC, 30 oC, 40 oC, 50 oC, 60 oC, 70 oC
• Crushed ice
• 6 boiling tubes
• One boiling tube rack
• 7 thermometers
• Pipette for measuring  cm3
• Distilled Water
• Stopclock
• Cuvettes
• Colorimeter

Potential errors in readings:

Systematic errors (value differing from the true value by the same amount) – any errors caused by the method is a systematic error as repeats will not improve the reliability of the results.

1. The markings on the ruler may not have been precise. Therefore each section cut form the beetroot may be uniformly slightly smaller or larger than the actual value.
2. There is constant heat loss to the surroundings from the hot water baths. The actual temperatures of the baths are therefore lower than the expected value. On the other hand, heat is gained from the surroundings for the ice as its temperature is lower than room temperature.
3. May not have been exactly 5 cm3 of distilled water measured out.

Random errors (values equally likely to lie above or below the true value) –

1. Some water may have evaporated in the 60 oC and 70 oC. This would have caused a higher colour absorbance reading due to the fact that pigment was concentrated into less water.
2. All the excess dye will not have been washed away, causing a higher colour absorbance reading.
3. Some of the pigment may have settled out in the cuvette, giving a lower absorbance reading if the light was shining above the precipitate.
4. The beetroot sections may not have been exactly the same length causing variations in the colorimeter reading. If the beetroot was only half an mm longer or shorter that would be thousands of more beetroot cells containing betacyanin. The beetroots may have also had different concentrations of betacyanin pigment.
5. The boiling tubes would not have been in the water bath for the exact amount of time due to the fact that it would be impossible to take out every tube at exactly 30 minutes.
6. Errors due to light intensity around the colorimeter.

Method:

1. Cut sections from a single beetroot using a size 4 cork borer. Cut six, 1 cm length slices from these sections using a ruler and knife. Remember to cut off the beetroot skin.
2. Place the slices in a beaker of distilled water. Stir the beaker until all the excess dye is washed away. This distilled water should be replaced at least twice.
3. After washing away the excess dye, place the six labelled boiling tubes each containing 5 cm3 distilled water in to water baths at 0oC, 30 oC, 40 oC, 50 oC, 60 oC, and 70 oC.
4. Leave for 5 minutes until the water reaches the required temperature. Use a thermometer to verify the temperature before putting in the beetroot. Record the actual temperature in the boiling tube onto a table.
5. Place one beetroot section into each boiling tube. Leave for 30 minutes in the water baths.
6. Remove the beetroot sections using a pair of forceps. Shake the solution to disperse the dye.
7. Switch on the colorimeter and set it to read % absorbance.
8. Using a pipette, accurately measure 2 cm3 distilled water into a cuvette. Place the cuvette into the colorimeter, making sure that the light is shining through the smooth sides.
9. Adjust the colorimeter to read 0 absorbance for clear water. Do not alter the setting again during the experiment.
10. Using a pipette again, place 2 cm3 of the dye solution into a colorimeter cuvette and take a reading for absorbency. Repeat the readings for all the temperatures, recording all recorded data onto a table.

Results:

Conclusion:

1. Due to spillages, we were unable to obtain results from the 10˚C and 20˚C water baths.
2. The results have proven my hypothesis correct. The increase of temperature did cause an increase in colour absorbance.

Discussion:

The increase in colour absorbency can be partially explained using the kinetic theory. When the beetroot molecules are heated in the beetroot, they vibrate and move faster. This then makes the phospholipid bilayer (part of the cell membrane) spread out, exerting a higher pressure on the cell membrane, causing the betacyanin pigments to spill out. The lipid structures in the phospholipid bilayer also become more fluid at higher temperatures, creating a fragile and more porous membrane.

The effect of heat on beetroot will also affect the proteins spanning the cell membrane. When heated, the proteins will untangle and break apart because of the vibrations associated with the kinetic theory. This will then form holes in the membrane, damaging the structure of the membrane, leaking the betacyanin pigments out from the cell vacuole.

If I had more time, I would have tested the beetroot using different pH solutions and also have taken more readings.