The effect of Ethanol on membrane permeability in Beetroot
The aim of this experiment is to find out how the concentration of Ethanol affects the permeability of beetroot cell membranes.
A eukaryotic cell, not only has a plasma membrane as its external boundary, but it also has a variety of membranes that divide the internal space into discrete compartments, separating processes and cell components. The complex and varied design of cell membranes gives them the remarkable properties that allow them to serve the variety of specific functions required by different types of cells. One of the most significant properties of membranes is selective permeability. This permits some molecules and ions to pass freely through the membrane, but excludes others from doing so. Understanding the structure and properties of cell membranes is important to understand how cells function.
Although the details of cell membrane composition and structure vary according to its specific function, all of them are composed of mainly lipids and proteins in a structure known as a lipid bilayer. This is a fluid structure that allows for the flexibility required for cell growth and movement in addition to the selective permeability that is so central to membrane function.
One component of plant cells that usually contains water is the vacuole, which is surrounded by a membrane known as the tonoplast. In beet plants, the vacuole also contains a water-soluble red pigment, betacyanin, which gives the beet its characteristic colour. If the tonoplast is damaged, however, the contents of the vacuole will spill out into the surrounding environment. In the case of beets, when the membrane is damaged, thered pigment will leak out into the surrounding environment. The intensity of colour in the environment should be proportional to the amount of cellular damage sustained by the beet.
This experiment allows you to test the effect of three different alcohols (methanol, ethanol, and 1-propanol) on cell membranes. Ethanol is found in alcoholic beverages. Methanol, sometimes referred to as wood alcohol, can cause blindness and death. Propanol is fatal if consumed. One possible reason why alcohols are so dangerous to living organisms is that they might damage cellular membranes, therefore resulting in the death of the entire cell.
Methanol, ethanol, and 1-propanol are very similar alcohols, differing only by the number of carbon and hydrogen atoms within the molecule.
The alcohol solutions used in this experiment are clear and colourless. If the beet pigment leaks into the solution, it will turn the solution red. The intensity of colour in the solution should be proportional to the amount of cellular damage sustained by the beet. As the concentration of pigment in the solution increases, it absorbs more light. In this experiment, the absorbance of light at 460 nm will be used to monitor the extent of cell membrane damage.
Scalpel / vegetable knife
5 Boiling tubes
Test tube rack
Serial Dilution Preparation
Collect the 5 boiling tubes and label them – 100%, 50%, 25%, 12.5%, 6.25% using the glass marker. Place them in the test tube rack.
Using the measuring cylinder, put 10cm3 of distilled water in boiling tubes – 50%, 25%, 12.5%, 6.25%
Then, put 20cm3 of ethanol in the boiling tube labelled 100%
Using the graduated pipette and the pipette filler, remove 10cm3 of ethanol from the 100% boiling tube and add it to the 50% boiling tube. Invert 3 times after sealing with the bung.
After that, take out 10cm3 of the solution, and add it to the 25% boiling tube.
Repeat the steps until all the tubes contain a solution of ethanol and water
Cut the beetroot in half using the scalpel / vegetable knife
Using the corer, retrieve 5 cylinders of beetroot from the centre. Use the spatula to gently remove the cylinder from the corer.
Measure each cylinder using the ruler and cut them into m0re similar lengths using the scalpel.
Fill the 250cm3 beaker with distilled water
Place the beetroot cylinders into the beaker to remove any Anthocyanin released due to the usage of the corer
Remove the beetroot cylinders after about 10-20 minutes.
Place each beetroot cylinder into a boiling tube containing an ethanol solution. Leave them in there for approximately an hour.
While waiting for diffusion to occur, collect the 5 cuvettes and calibrate the colorimeter.
After an hour has passed, remove 3cm3 of each solution and place it into a cuvette for absorbance testing.
Place each cuvette into the colorimeter and test the absorbance. Record the result. If possible, complete more than one trial to ensure errors are minimised.