To investigate the effect of different organic solvents, such as alcohol and paraffin oil, on the cell membrane of the beetroot by using the red pigments in the beetroot as indicator.
Organic solvents dissolve the organic matter in the cell membrane (such as phospholipids). This destroys the cell membrane, and the permeability of the cell membrane is disrupted casing red pigments to leak out by diffusion.
The cell membrane is mainly made up of phospholipids and proteins. The phospholipid molecules are arranged in a bilayer. And there are some proteins molecules are interspersed among the phospholipid bilayer. This structure makes the cell membrane differentially permeable. Thus, some large molecules can’t pass through the cell membrane. The cell membrane can be destroyed by physical damage and chemical. When the cells are cut, the cell membranes are mechanically ruptured. Some chemicals such as organic solvents can dissolve the organic matter in cell membrane, causing damage of the membrane and therefore increased permeability. This leads to an easier leakage of contents of the cell.
Type of variables
Representing variables in this experiment
Color of the organic solvents change
Concentration of organic solvents and kinds of organic solvents Control variable
Temperature of organic solvents used and the surrounding
Volume of organic solvent used
Time for the reaction
Control set-up: 3 ml of water with beetroot for 5minutes reaction This set-up are used to show if there are the same effect as in organic solvents
The volume of the red pigments in each of the beetroot cell is equal.
Water, 10% alcohol, 20% alcohol, 30% alcohol, paraffin oil
Beaker X1, cloth X1, test tube X6, test tube rack X1, forceps X1, measuring cylinder X1, white tile X1, glass rod X1, cork borer X1, blade X1
1. Label six test tubes as water, 10% alcohol, 20% alcohol, 30% alcohol, paraffin oil, paraffin oil + water.
2. Use the measuring cylinder to measure 3 ml different organic solvents and water.
3. Transfer the solutions to the test tubes and cover it with stopper (except paraffin oil + water one).
4. Cut the beetroot samples (in same size) by using cork borer and blade.
5. Fill up half of the beaker with water.
6. Dip the beetroot samples into the water by using forceps.
7. Wash away the pigment which appears on the surface of the beetroots. Then, dry it.
8. Put the sample into the 5 test tubes and wait for 5 minutes.
9. Measure 3 ml water and transfer it to the ‘paraffin + water’ test tub.
10. Take out the samples from the test tubes. Sample that take out from the paraffin oil need to dry it up. And put it into ‘paraffin + water’ test tub.
11. Wait for 5 minutes.
12. Take out the beetroot sample from the test tube.
13. Observe the color.
Beetroot contains a red pigment called betacyanin, which is soluble in water. And it located in the large central vacuole of the beetroot cells. These red pigments will remain inside the cell if the cell is intact. Thus, this can be used as an indicator for cell membrane permeability. The red pigments can’t leak out from the cell under normal condition. This is because the red pigment is too large and can’t pass through the differentially permeable membrane. But when the beetroot samples are put into the organic solvent, the cell membrane are destroyed. This increases the permeability of the cell membrane. Also, the concentration of the red pigments is higher in the cell than the organic solvents. Thus, the red pigments can leak out from the beetroot cell by diffusion. The alcohol and water give the results as the red pigments leak out but paraffin oil doesn’t. There are very little red pigments leak out from the beetroot, which are first soaked in paraffin oil and then in the water. By increasing the concentration of alcohol, the red color becomes deeper. This is because the higher concentration of the alcohol, the faster rate of destruction on cell membrane, and the higher permeability. This cause the more intense of red color showed. There are no red color come out from the paraffin oil.
We take out the beetroot sample from the paraffin oil and then put it in the water. The reason of this step is to find out if the paraffin oil destroy the cell membrane and increase the permeability. And in our result, there are only very little red pigments come out. This show that paraffin oil doesn’t dissolve the cell membrane well. Water is not an organic solvent. Therefore, it doesn’t dissolve the cell membrane and cause the leakage. But, our results show that the beetroot sample in water leak out lots of red pigments. And the samples in different concentration have similar intense of red color. There are some possible errors which cause this result. First, we haven’t washed away the red pigments which are produced by the cutting of beetroot samples. Some of the red pigments are still attach to the surface of the beetroot samples. Moreover, the volume of the chemicals used in the experiments maybe is not enough to show the color clearly. Furthermore, the beetroot used maybe is not fresh and the cell membrane of it may be destroyed already. And this causes the higher permeability. To improve this experiment, we can increase the volume of the organic solvents and water used in the experiment. And also, we can wash the cutting beetroot until no more color appeared in the wash water. This can make sure the red pigments which leak out because of the cutting will not affect the result.