Equipment
Half a beetroot
Scapel
Glucose solution
Distilled water
Colorimeter
Test tubes
Stopwatch
Core borer
Water bath
White tile
Clamp
10 cm3 Measuring cylinder
Diagram
Experimental Method
Prepare 5 test tubes and label them: 20%, 40%, 60%, 80%, 100%.
To prepare these different glucose concentration solutions, use 2 different 10cm3 measuring cylinder, one for water, and one for the glucose to ensure accuracy.
The table below shows the amount of glucose and distilled water need to prepare different glucose concentrations.
Obtain long pieces of beetroot from a cork borer. First push the cork borer vertically into the beetroot. Then, use a thin spatula to push the cylindrical beetroot piece out from the cork borer. Use a scalpel and cut the long pieces of beetroot into 2cm pieces each. Measure it with a ruler to ensure sizes are consistent.
For each test tube, put one 2cm piece of beetroot in. Leave beetroot in solution for 10 minutes. Use a stopwatch to determine the time accurately.
Remove beetroot pieces out of the glucose solutions using a long tweezers. Be careful not to clamp the beetroot too hard when taking it out as excess pigment may be released which may affect final results.
Measure the light transmission percentage of the pigment released from the beetroot in the solutions by using a colorimeter.
Repeat the above instructions 4 more times in order to get 5 sets of readings for the results.
The experiment will be repeated 5 times to ensure that the results may be as accurate as possible and to also be able to obtain an average. This is also to reduce the errors caused during the experiment thus improving the overall successfulness of the experiment.
Risk Assessment
Lab coats and safety goggles would be worn during the experiment to prevent a lower risk of harmful chemicals to contact our skin
Be cautious when using the core borer and knife as blades are sharp
Long hair would be tied back
Sandals and flip-flops would not be worn during the experiment. Shoes covering the feet have to be worn.
Raw data results table
Data collection and Processing
Raw data table to show the effect of glucose concentration of cell membrane permeability
Calculating standard deviation (of 20% concentration of glucose)
Standard deviation =
Standard deviation for 20% concentration of glucose:
(37-35.2)2 + (35.2-35) 2 + (35.2-33) 2 + (39-35.2) 2 + (35.2-32) 2 = 32.8
SD= √ (32.8/5)= 2.6
Observations
From observations, after the beetroot pieces was emerged into the solutions for around 10 minutes, I noticed that the solution with 100% glucose concentration was darker in colour (a crimson red) than the 20% glucose concentration one with a light pink colour. I also noticed that the lower concentration solutions such as 20-40% causes the beetroot to float up to the surface of the test tubes while the higher concentration solutions such as 80-100% would sink to the bottom.
Analysis
The first table of results was presented to show how I calculated the different concentration of glucose percentages from interpreting the glucose to water ratio. I did this by dividing the amount of glucose by the total amount of solution there is which is 10cm3 then times by 100 for the percentage. For example, 4ml of glucose divided by 10ml times by 100 would be 40%. Therefore the concentration of 4ml glucose by 6ml water would be 40% concentration of glucose solution.
The second data table shows light transmission percentage after beetroot pieces are soaked in different concentration glucose solutions for 10 minutes. The light transmission percentage tends to decrease by around 1-5% each time as the concentration of glucose increases.
I calculated the standard deviation and found out that my results are statistically significant which means it is unlikely it has occurred by chance. The significant result also means that there is a relationship between the two variables- concentration of glucose and the light transmission percentage. From analyzing the graph, we can see that most of the error bars overlap especially the first 2 values for the 20% and 40% glucose concentration. Therefore, this proves that the data may be statistically significant as the difference between the averages is quite large as seen in the graph from the overlapping error bars. However, this may also indicate that there are errors and uncertainties in the experiment as the standard deviation numbers are quite big.
Conclusion and Evaluation
The objective of this experiment was to determine whether different concentrations of glucose would have an effect on the permeability of cell membranes of beetroot cells in which they would release a red pigment called betacyanin. In conclusion, the results I have obtained has proven by hypothesis (stating that the higher the concentration of glucose, the lower the light transmission percentage) to be correct. My data tables can also support this theory. When it was 20% concentration of glucose, the average light transmission was 35.2% and when the concentration of glucose was 100%, the average light transmission was 22.6%. Also from observation, I could see that as the concentration of glucose increases the solutions went darker in colour. In my results table, I did not find any anomalous results.
The biological reason to why the concentration of glucose would affect the beetroot cell membrane permeability is because the solutions have a low water potential. A glucose solution will affect the water potential in the beetroot cell. Having a low water potential, the water will exit the cells by osmosis as it goes from a level of high water potential in the beetroot cells to lower water potential in the glucose solution. In the long term, due to a highly concentrated glucose solution, the cells will become flaccid and begins to wilt. Therefore the cell membrane will detach from the cell wall causing it to increase permeability and the stability to decrease and will allow more solutes into the cell.
The standard deviation error bars as seen in the graph overlaps each other which means that which means the readings in each trial is significantly different from the average of all the trials indicating that there may be errors and uncertainties involved in the experiment. This shows that my data may not be very reliable as the errors cause the results to be significantly different.
Weaknesses and improvements
Cite references
"Cell Membrane." Wikipedia, the Free Encyclopedia. Wikepedia.org. Web. 12 Jan. 2012.
Brown, Catrina, and Mike Ford. Chemistry: Higher Level : Developed Specifically for Thr IB Diploma. Oxford: Heinemann, 2009
This is a draft up of the raw data table that I will be using when I put in my readings from the experiment. It includes column with headings the concentration of glucose solutions by light transmission percentage, 5 trials, average and the standard deviation.