TEMPERATURE ON BEETROOT PERMEABILITY
AN INVESTIGATION INTO HOW TEMPERATURE AFFECTS THE PERMEABILITY MEMBRANE OF A BEETROOT.
TASK IN BRIEF
For this experiment, I am investigating the effect of temperature on the permeability of a beetroot membrane. First thing I did was I measured out 5 100cm³ of distilled water, and placed them into 5 different temperatures. Using the cork borer, I cut out one cylinder for each temperature, and then trimmed to a length of 2.5cm. After, I put the trimmed beetroot into the 5 different temperatures and left them for 25minutes. After 25miutes, I decanted the liquid containing the leaked beetroot pigment at each temperature into a cuvette, and then placed it into a calorimeter which has a blue filter. Then I measured the percentage light transmission for each temperature. And lastly I collected results for others in class to use it for comparison.
I believe that more betalain pigment will be released from the beetroot as the temperature increases. High temperatures may distort the active site of the carrier affecting the shape of the fluid mosaic model membrane. The increase of kinetic energy will speed up the diffusion rate of the red pigment to a point. Then the structural damage of the membrane and the denatured proteins will increase the amount of red pigment escaping out of the cells.
TABLE OF RESULTS
Table to show the percentage light transmitted through a beetroot pigment (betalain) at different temperatures in an experiment to investigate the effect of temperature on the permeability of a beetroot membrane.
- These are all the group results.
- My results are the first set of results
- The anomalous results are in bold italics.
ANALYSIS, EVIDENCE AND CONCLUSION
Mean of class calculated to give more reliable data for conclusion and to use it to produce graph and standard deviation.
Looking at the result table and the graph produced from the results obtained form this experiment; it shows that as temperature increases, the percentage transmission decreases. This tells us that temperature does affect the membrane, resulting in more leakage of the red pigment. The beetroot solution appears as a red colour and this is caused by the betalain pigment contained within the vacuole of beetroot cells.
An overall description of the graph shows that as the temperature increases, the percentage light transmission decreases. Increase in temperature shows that more pigment is leaking out of the membrane, showing the membrane as getting more permeable.
From 0ºC to 18ºC, it shows that low temperature has little effect on the beetroot’s membrane, because there’s a very slight decrease of light transmission (shown by observing the graph, there’s a slight decrease of light transmission between the two temperatures). This is because the temperature is too low, resulting in the beetroot’s particles having less kinetic enerygy, with the betalain pigment having less energy for a collision to occur. The low temperature won’t cause much damage to the beetroot’s membrane because the phospholipid bi layer has prevented the betalain pigment from leaking out due to polarity; because the phospholipid bi layer acts as a barrier to stop water soluble from moving in and out of the membrane. And since the betalain pigment is water soluble, at low temperatures, the phospholipid bi layer is still acting as a barrier, stopping it from leaking out of the beetroot’s membrane.
From 18ºC to 35ºC, there’s a rapid decrease of light transmission (and looking at the graph, it shows the biggest steepness out of all the other temperatures). This is due to the input of kinetic energy due to the build up of temperature that increases the rate of diffusion, and the increase in temperature causes a vibration. This in turn will damage the plasma membrane causing substances contained within the membrane to leak out. It is the breakdown of phospholipids in the membrane, which cause gaps to appear, allowing fluids (red pigment in this case) to pass through. As the red pigment particles
move faster, they diffuse out of the membrane at a faster rate, increasing more as the temperature increases.
This is a preview of the whole essay
At low temperatures e.g. 0°C to 35°C, some tonoplast (vacuolar membranes) and the cell membrane will leak into the surrounding water but at a much higher temperature, the tonoplasts of the cells will break down completely, resulting in a massive release of betalain pigments. Because the temperature has not gone beyond what the membrane is supposed to withstand, the permeability of the plasma membrane was not really affected at low temperatures (5°C to 35°C). But since the temperature has goes beyond limits that the membrane can withstand (temperatures from 35°C upward), then liquid solution (betalain pigment) in the membrane expands, putting pressure on the membranes from within. The lipid part of the membrane liquefies, making it more prone to leakage. The proteins that span the membrane fall apart, creating holes in the membrane. All this combined caused the betalain pigment to leak out of the beetroot’s membrane. This happens because higher temperature makes the beetroot’s molecules to shake and vibrate more. The faster movement disrupts any ordered structure that might have been in the membrane, eventually destroying the beetroot’s membrane structure altogether. At also at high temperature, the betalain pigment of beet root cells is normally sequestered in the vacuole and by means of the cell membrane which maintains the integrity of the cell and the tonoplasts, it does not leak into the cytosol or the extra-cellular sap of the beet root. However when we increase the temperature the relatively weak forces holding the different parts of the polypeptide chains together (like hydrogen bonds, sulphur bridges and ionic bonds) can be disrupted very easily- this damages the vacuole and makes holes in the cell membrane, inducing more leakage of the betalain pigment.
Observing the results, at 54°C to 67°C, the percentage light transmission tends to be either the same, or 67°C is 1% lower in light transmission than 54°C. This is because once the cell membrane of the beetroot is broken; no difference is made on how much pigment is released. If I had done another temperature preferably at a temperature above 67°C, I would have gotten the same % of light transmission as I did for 67°C. When a protein is denatured, the and are altered but the between the amino acids are left intact. Since the structure of the protein determines its function, the protein can no longer perform its function once it has been denatured. And because once a protein is denatured it can no longer be used by the body as it lacks its necessary structure and as the protein function is dependent upon this, it becomes useless, so the diffusion of the betalain pigment remains constant. Looking at the graph, the reason why the amount of betalain pigment increases gradually (from 35°C to 67°C) is because most mammalian protein's denature and tertiary structure unravels (the strong covalent bonds between the R groups of amino acids in the polypeptide chains are destroyed) at temperatures over 40°C. And the reason why the curve starts to flattens out (between 54°C and 67°C), is because although the denaturing of the protein causes a rapid rise in the amount of betalain released to start with, when the temperatures still continues to increase, the protein's tertiary structure blocks some of the holes in the cell membrane and therefore slows down the release of betalain.
From the results, I found out that low temperature don’t affect the membrane of a beetroot in comparison to high temperature which result in more leakage of the betalain pigment. And after the optimum temperature of the protein (around 40°C), the protein gets denatured, causing a change in the 3D shape of the protein, and resulting in more pigment been leaked. And when the protein is fully denatured, the percentage of light transmitted will be constant.
The 3D structure of the beetroot’s membrane (as shown in fig 1) is made up of, cholesterol, proteins, glycolipids and glycoproteins. Each of these all has specific functions in the cell membrane.
The purpose of a cell membrane is to control the transport of substances moving into and out of a cell. The membrane is an extremely thin layer (8 to 10 manometers (nm)) thick, which is partially permeable. It consists mostly of lipids and proteins. Proteins are more likely to withstand higher temperatures of 50 °C, but once proteins have denatured they are no longer able to carry out there function.
The lipids found in cell membranes belong to a class known as triglycerides, so called because they have one molecule of glycerol chemically linked to three molecules of fatty acids. Lipids tend to liquefy at high temperatures causing ruptures in the plasma membrane. The majority belong to one subgroup of triglycerides known as phospholipids.
Phospholipids make up the basic structure of the membrane, forming a bi layer. They have hydrophilic heads and hydrophobic tails, with the tales being non polar it is very difficult for ions and polar molecules to pass through the membrane, so the phospholipids act as a barrier to water soluble molecules.
Therefore the only way water-soluble molecules can get through the membrane is through the protein. Protein in the membrane acts as hydrophilic passage ways or transport route for ions and polar molecules to diffuse into the membrane. Protein control what substances enter and leave the membrane. There are specific protein types for different substances; these are known as protein carrier cells.
Cholesterol role is different compared to protein and phospholipid, its role is to give the membrane support and strength. Cholesterol determines how fluid the membrane is. It helps to control the fluidity; stopping it from becoming too fluid or too rigid, preventing the membrane from bursting. Cholesterol structure is very similar to a phospholipid; it too has a hydrophilic head and hydrophobic tale, which allows it to fit neatly in the phospholipids.
Glycolipids and glycoproteins role is to help stabilise the membrane, with their carbohydrate chains that extend out into the water surface forming hydrogen bonds with the water molecules.
Lastly, the lower the temperature the more light is transmitted because less concentrated betalain pigment is produced due to the membrane been not very permeable. And for the higher temperature, the less light is transmitted because more concentrated betalain pigment is produced due to the membrane been more permeable. Since the lipid bi layer gives the membranes its fluid characteristics. And at low temperatures, the bi layer is in a gel state and tightly packed. But at high temperatures the bi layer "melts' and the interior becomes fluid allowing the lipid molecules to move around, rotate and exchange places. This also allows movement of other components of the membrane. And this fluidity in the membrane has caused a great leakage of the betalain pigment in the beetroot’s membrane.
The procedure is suitable because I obtained the result I expected i.e. as temperature increases, the membrane becomes more permeable. The equipment used are mostly accurate (e.g. the water baths), because it allowed us to carry out the experiment in an expected way. The prediction does however matches with the results derived from the experiment, which concludes that high temperatures does makes the membrane more permeable due to the membrane becoming more fluid.
The two anomalous results for 5°C is 16% and 18% light transmission. These two are higher than the other results which don’t fit in with them. This makes me think that they are too high light transmission to occur at 5°C. These anomalous results may be from the fact that we didn’t put our test tubes in the same water baths containing ice, we all had to get our own ice using a beaker, and then set it up ourselves. This means that some of us may have some slightly higher temperatures than others, which could be the error that has resulted in these anomalous results.
For 18°C it also has two anomalous results. This is 15% and 5%. 15% is too high whereas 5% is too low for light to be transmitted at 18°C. This error is likely to have occurred due to the fact that we all took out our beetroots from the water baths at different times. So more or less damage may have occurred to the membranes of the beetroot, depending on how long each of us left our beetroot for in the water baths resulting in more or less pigment getting leaked.
For 35°C, there is a low light transmission of 3% which doesn’t fit with the other results because it’s slightly lower. This anomalous result may have occurred due to the fact that we didn’t get an accurately straight beetroot, because some of the beetroot when cut were “wobbly”. This would have affected the shape of the beetroot resulting in different rates in which the beetroots membrane is damaged for each of us in the class.
Another anomalous result is for 54°C, and it’s for 8% light transmission. This is slightly higher than others in the same group. This may have occurred because it’s hard to get an accurate cutting of 2.5cm for the beetroots. The inaccuracies of the cuttings may have resulted in this error.
The last anomalous result is for 67°C which has a light transmission of 7%. This is too high percentage light transmission than expected. The error may have been from the shaking of the test tubes, which people did shake and some people didn’t. If the test tubes was shaken too much then more betalain pigment would have been further released however, this 7% error may have been as the result of the test tube not shaken well enough, resulting in very little emission of the betalain pigment.
Looking at the standard deviation, 67°C was the most reliable and accurate. This is because it has a standard deviation of 1.2 which is much closer to zero than any of the other results. Whereas, 5°C seems to be the least accurate, having a standard deviation of 4.4, this is more widely spread than any of the results. The reason why 67°C is looking reliable and accurate than any of the other results may be because of the beetroot’s membrane been already denatured. So even if the temperature is 65°C or 69°C, the same data of results for 67°C would still be derived. Whereas for 5°C, the ice used may have been in different conditions (i.e. some water more iced than others). Using the standard deviation to choose how accurate the results are, 67°C is the most accurate, followed by 54°C, then 35°C, then 18°C and lastly 5°C. There’s a pattern in this, and it’s the higher the temperature, the more accurate the results are and lower temperature shows to be slightly less accurate. This is shown by the results derived from the standard deviation.
There were some limitations in the experiment. This has affected the results, by making them less accurate than it should have been.
Numbers is used to rank the error in accordance to how each limitation will have the most or the least impact on the experiments. 1 for most and 7 for least.
Overall, the evidence is quite reliable in showing that higher temperature does have an effect on the permeability of a beetroot’s membrane. The main source of error is using a wide range of temperatures. The temperatures used for this experiment are too widely spread i.e. from 5°C to 18°C to 35°C etc. if a closer range of temperatures is used, then the result would have been more reliable than it is. Another main source of error is not blotting out the beetroot to remove leaked betalain pigments before putting it in distilled water. This is because the membrane is already damaged, and blotting it out removes all leaked pigment, this means more precise results will be obtained.
An error with the least impact is the straightness of the beetroot because we are not measuring how straight the beetroot is, but how easily permeable the membrane of the beetroot is. Straightness does not have much of an impact on the permeability of a beetroot’s membrane.
If all improvements is taken into use when doing this experiment again, then the result obtained will be far accurate than the one I have now.
Finally, the beetroot gives a good representation of the theories behind the plasma membrane and how it behaves but it does not give a good representation of the whole eukaryotic group because their behaviour may differ to others.