The effect of alcohol concentration on the cell membrane

Categories: Alcohol

In this experiment I found out that as the concentration of the alcohol was increased so did the colour intensity of the solution. This is because the higher concentration of ethanol, results in more damage done to the cell membrane, resulting in leakage of red pigment from the cell. If the membrane is damaged more, more red pigment will leak out of the membrane and into the ethanol. Hypothesis:

The higher the concentration of ethanol the more permeable the cell membrane will become.

The cell membrane is a thin semi permeable membrane which surrounds the cytoplasm of the cell. The cell membrane controls whatever enters and leaves the cell. All animal and plant cells have cell membranes.

Phospholipids- This is the major component to the membrane. Hydrophobic tails and hydrophilic heads will automatically form a bilayer. This ensures that the tails stay in the centre where they are not in contact with water and that the heads are in contact with water.

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This bilayer results in polar substances being able to diffuse through the membrane similarly like small non-polar molecules (oxygen) also diffusing through the membrane.

Cholesterol- The main function cholesterol performs is providing stability for the membrane therefore making it less fluid. It is a type of lipid and fits in between the phospholipids causing them to pack tightly together.

Proteins- Proteins control whatever enters and leaves the cell. Carrier proteins allow certain substances into the cell. Proteins also act as receptors for hormones in cell signalling.

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Glycopids & Glycoprotein’s- these stabilise the proteins and act as receptors for messenger molecules in cell signalling. This structure can be affected by alcohol as it isn’t a polar molecule so the phospholipids would not form a bilayer. Also a high temperature would denature the proteins because they are made up of amino acids. Equipment:

8 test tube –to hold the different concentrations of ethanol
Test tube rack-to hold the test tubes and preventing them from falling
Cork bore – to have the same diameter of beetroot pieces
Graduated pipette- accurate measurement of ethanol
Colorimeter- accurate measurement of the absorption at 55nm
8 Cuvettes- only use clear ones
Pins – to pick up the beetroot (stains your hands)
Ruler – measuring out the beetroot
Scalpel- to cut the beetroot
Beetroot- will be testing the beetroot membranes
Ethanol – at the concentrations of 10%,20%,30%,40%,50%,60%,70%( 〖5cm〗^3 of each)
Distilled water- 〖5cm〗^3
Stopwatch- to ensure all the beetroot are in the ethanol for the same time

Control variables:
Keep the same thickness of beetroot (use the same cork bore)
Use Same batch of beetroot
Use the same filter on the colorimeter (550nm)
Make sure the beetroot pieces are in the ethanol for the same time Dependent variable:
The absorption of the red pigment at a filter of 550nm.
Independent variable:
The different concentrations of ethanol.
First lay out the 8 test tube and place them carefully into the test tube rack.
Carefully measure out 〖5cm〗^3 of distilled water with a graduated pipette. Then empty the pipette out into the first test tube.
Repeat this process but for the different concentrations of ethanol as they increase. Make sure to place the test tubes of the different concentrations of the ethanol starting with 10%, then 20% and so forth in order. This is so you can remember which percentage is where.

Next carefully pierce your beetroot with the same cork borer and remove the beetroot piece.
Using a ruler, measure out 8, 1cm cylinders of beetroot.
Cut them carefully using a scalpel.
Now you will have to place the beetroot pieces into all the different test tubes. As soon as you have done this start the stopwatch for 20 minutes.
Swirl the test tube at 10 minutes to allow the beetroot and alcohol to mix.
Once 20 minutes have passed, get a pipette and fill each cuvette up with the different solutions.
Now it is time to use the colorimeter. Use the filter550nm. Fill a cuvette with normal water and put it into the colorimeter and press reset and then test.
Now do this for the distilled water and press reset and then test. After each test you need put the normal water back into the colorimeter to reset it.
Repeat this for all the solutions and take a note of your results.

Ethanol concentration (%)Absorption (nm)
Test 1 Test 2 Test 3 Mean Average

From this experiment I have found out that my hypothesis was correct, but only to a certain extent. As you can see from my results it is clear, that as the alcohol concentration increases there is a significant increase in the absorption also; there is a positive correlation between the two.

However my results are not fully reliable as I have a lot of anomalous results which would need repeating. Also there could have been other factors which affected cell membrane permeability such as the temperature change; to eliminate this factor I would have to place the test tubes in a water bath, to keep them at a constant temperature throughout the experiment.

Also when I was moving the beetroot pieces with the pin they were being pierced and this results in cell membrane damage and some pieces could have been pierced more than others so would be more permeable. All of my results do not increase as the concentration increased and this could be a problem. Overall there is a positive correlation but there are many other factors to be taken into account.

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The effect of alcohol concentration on the cell membrane. (2016, May 13). Retrieved from

The effect of alcohol concentration on the cell membrane

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