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Investigating the Effects of Temperature on Cell Membranes

Investigating the effects of temperature on cell membranes Independent variable: Temperature of beetroot Dependent variable: Absorbency of light Hypothesis: As temperature rises to its optimum temperature, the absorbency of light will increase because protein is an enzyme and will therefore be affected by temperature. This is because more beetroot dye will pass through the cell membrane and then into the distilled water. The deeper the colour of the beetroot dye, the higher the absorbency of light.

Beetroot vacuoles have red pigments which can’t pass through the cell membrane there will therefore be an increase in the amount of red pigment diffusing out of the cell. This is because there is a high concentration of red pigment in the cell and no concentration in the water. Increasing the temperature will also provide kinetic energy to the phospholipid bilayer, increasing the movement of the individual phospholipids – this will cause gaps to appear allowing the dye to pass through.

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Membrane proteins may be denatured by the higher temperatures and their tertiary structure will unravel also allowing dye molecules through the membrane. Apparatus: * Access to several water baths set at a range of temperatures, or beakers containing water at different temperatures (note 3) * Thermometers, 1 for each water bath * Kettle, to provide boiling water for the water baths * Ice bath (a beaker of water surrounded by ice) * Scalpel, 1, or sharp vegetable knife * Tile, 1 * Forceps or mounted needles to ‘handle’ beetroot cores * Ruler, up to 15 cm, 1 Distilled water, in wash bottle * Measuring cylinder, 10 cm3, 1 * Test tubes, 1 for each temperature of water bath * Paper towels * Marker pen Temperature / °C| Absorbency / A| | 1| 2| Mean| 0| 0. 24| 0. 28| 0. 26| Room temp (22)| 0. 39| 0. 41| 0. 4| 40| 1. 22| 1. 31| 1. 25| 60| 2. 00| 2. 00| 2. 00| Method: 1. Collect 3 or 4 beetroot cores from the beaker provided. Cut each core into 2 cm sections until you have enough for one core for each temperature of water bath that you will be using. Put your 2 cm sections into a test tube with plenty of distilled water. 2.

Label a set of test tubes (one for each temperature of water bath) with the temperature and your initials. Add exactly 5 cm3 of distilled water to each test tube and place the tubes, one in each water bath, for 5 minutes to equilibrate to the water bath temperature. 3. Remove the beetroot cores from the distilled water and blot gently on a paper towel. Decide whether forceps or mounted needles are best for handling the tissue and what damage this might cause to the cores. 4. Place one 2 cm beetroot core into each test tube and leave in the water bath for 30 minutes 5.

After 30 minutes, shake the test tubes gently to make sure any pigment is well-mixed into the water, and then remove the beetroot cores. 6. Describe the depth of colour in each test tube. A piece of white card behind the tubes will make this easier to see. Arrange the tubes in order of temperature of the water bath. Describe any relationship between the amount of pigment released from the beetroot and the temperature. 7. If you have access to a colorimeter, set it to respond to a blue/ green filter (or wavelength of 530 nm) and to measure absorbance.

Check the colorimeter reading for distilled water. 8. Measure the absorbance of each tube and plot a graph of absorbance against temperature. Describe any trends or patterns in your results. GRAPH Conclusion: The graph shows that as temperature increases between 0 and 60 °C the mean absorbency of light increases from 026 A to 2. 00A, showing a positive correlation. Between 0 and 40 °C the rate at which the temperature vs. absorbency increases is low however between 40C and 60C the rate of increase is much faster and the light absorbency increases from 1. 5 A to 2. 00. After collecting and correlating the results, I have come to the conclusion that the hypothesis is correct in that an increase in temperature will cause an increase in the absorbency of light. Higher temperatures provide more kinetic energy to the cell membrane which consists mainly of a phospholipids bilayer and membrane proteins. The phospholipids movement and fluidity will increase and beetroot pigment molecules are able to move through gaps between individual phospholipids and out through the membrane.

The graph also indicates that past 40C the cell membrane became more permeable and allowed a greater diffusion of the red beetroot pigments into the distilled water. It also highlights that 60C would be the optimum temperature for proteins in beetroot storage tissue cell membranes to facilitate diffusion as this is the highest point the line rises to, it is thought that if we had continued the experiment past 60 degrees that the line would have decreased back to 0. Evaluation: Precision * We used the colorimeter which is a piece of precise electronic equipment which measured absorbency.

It therefore had no human error which very much helped the experiment become more precise. * We used a pipette to distribute the beetroot solution into the cuvette. But it only had a scale of only 0. 25 ml and it was difficult to measure the volume of water in it as the water slowly dripped out of the end. * But we did not measure the volume of distilled water into the boiling tubes very precisely as it was only a matter of guessing it against others. We also did not have any apparatus to pour the distilled water into the boiling tube. Reliability Unfortunately because we were constricted by the time of the lesson, we were not able to obtain 3 different sets of results. This therefore means that our results cannot be fully reliable. * However saying that, a mean was taken from the two results that were obtained and the experiment did still seem to fit the hypothesis. * A problem from the results is that between the temperature differences there are huge gaps in results as to what happened between 40 and 60 degrees and therefore we do not know if it is specifically temperature as a factor that contributed to the increase in ight absorbency. * But from the last set of results at 60 degrees, the light absorbency was identical and the other sets of results were very close. To improve the results further steps could be taken to repeat them 4 or 5 times and obtain a mean, this will also contribute to making the experiment all round a more accurate one. Validility: We obtained valid results by keeping the control variables as constant as possible and only varying the temperature of the water surrounding the beetroot- in order to be able to measure one variable in the experiment against another. Volume of water in test tube measured with measuring cylinder. * Volume of beetroot cylinders kept constant using cork borer then cut to precise length against ruler. * All beetroot cylinders were kept in water for the same time, measured to the nearest minute. Although there were several inaccuracies in the experiment, such as the method of measuring the distilled water, the lack of precise method of measuring beetroot (i. the curvette) , the lack of precision of measuring the beetroot cylinders ends (cut at an angle or human error) and the water baths perhaps being at an inaccurate temperature. If enough time was given, you could definitely improve the experiment by; repeating it 3 times to obtain accurate results, using a more precision method of measuring the beetroot solution; perhaps checking for errors on the Colorimeter and trying to control as many confounding variables as possible, then this experiment could become much more accurate and provide a very precise result.


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