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Design an experiment to investigate the effect of temperature on the movement of a pigment through a membrane

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Introduction

Design an experiment to investigate the effect of temperature on the movement of a pigment through a membrane Hypothesis The tonoplast is the membrane that separates the vacuole from the rest of the cell. The membrane is selectively permeable and a phospholipid bilayer. The membrane is made up of phospholipids, which have a phosphate group and two fatty acid tails. The phosphate group is polar and hydrophilic, whereas the fatty acid tails are non-polar and hydrophobic. The fatty acid tails therefore try to get as far away as they can from the watery fluid in the vacuole and the watery cytoplasm, so the fatty acid tails point inwards and the phosphate heads point outwards. Also in the bilayer there are proteins, which can be intrinsic or extrinsic. Intrinsic proteins are proteins that span the full width of the membrane, whereas extrinsic proteins only go a small way into the membrane. The proteins provide structural support, act as carriers for water-soluble substances, can act as enzymes, form ion channels and they can act as receptors for hormones. Carbohydrate chains can join to the extrinsic proteins forming glycoproteins. These act as recognition sites. Carbohydrate chains can also join to the phospholipids forming glycolipids, this act as recognition sites and helps the stability of the membrane. Also there is cholesterol in the membrane this prevents leakage of water and ions from the cell, and therefore reduces the movement of the phospholipids, giving the membrane stability. This whole structure of the tonoplast is called the fluid mosaic model. This is because the phospholipids and proteins in the membrane are continuously moving and the membrane resembles a mosaic in appearance. Below is a diagram of the phospholipid membrane. (Source- http://fig.cox.miami.edu/Faculty/Dana/membrane.jpg) As the temperature increases the membrane becomes more fluid because the individual molecules have extra energy so they move around more. Furthermore at I think that the cholesterol molecules would also be affected by temperature, this would mean that the membrane would become even more fluid at high temperatures, because of the affect of cholesterol on the membrane. ...read more.

Middle

9.42 -3.42 11.7 2 13 9.42 3.58 12.8 3 16 9.42 6.58 43.3 4 3 9.42 -6.42 41.2 5 11 9.42 1.58 2.50 6 12 9.42 2.58 6.66 7 14 9.42 4.58 21.0 8 10 9.42 0.58 0.336 9 5 9.42 -4.42 19.5 10 6 9.42 -3.42 11.7 11 8 9.42 -1.42 2.02 12 9 9.42 -0.42 0.18 Sum ? x2= 113 ?(x2-x2)2= 172.896 = 173 (3sf) Variance= ? (x1-x1) 2 n-1 = 173 11 = 15.7272... = 15.7 (3sf) Standard deviation = V15.7 = 3.96 (3sf) t = x1 - x2 V s12 + s22 n1 n2 t = 89.2- 9.42 (4.282/12)+ (3.962/12) `= 28.15764.... = 28.2 Degrees of freedom= n1+n2 -2 = 12+12-2 = 22 Gradients of lines I have used the averages excluding the anomalies to calculate the gradient of different line segments on my graph. Gradient of line segment from 35�C - 45�C y2-y1 =90-97 = -0.7 x2-x1 45-35 Gradient of line segment from 50�C - 60�C y2-y1 =21-81 = -6 x2-x1 60-50 Gradient of line segment from 65�C - 80�C y2-y1 =2-10 = -0.53 x2-x1 80-65 Analysis I used results from pooled data of my biology class. This is because the more data that I have the more likely it is that my results are accurate. In my table I have highlighted the anomalous results and I have done two averages, one including my anomalies and one excluding them. This is to show the affect that my anomalous results have on my graph and on my results. My results show that as the temperature increases there is a lower transmission of light through the solution of water and pigment. My graph is a sigmoid shape. The graph showing the results including my anomalies has a steeper gradient at the top and bottom of my graph, whereas the one excluding my anomalies has a gentler slope at the top and bottom. ...read more.

Conclusion

I then cut each of the columns of beetroot into 4cm pieces, measuring them using a ruler to ensure that they were exactly the same length. To improve this I could use a more accurate way of measuring the length of the beetroot than a ruler, this is because it is hard to measure the length of the columns of beetroot with a ruler, since they are round and the ruler is flat, so you cannot see the ends of the beetroot exactly. Colorimeter 8 The colorimeter caused errors in the data produced. This is because after it had been used to measure the percentage transmission a few times, it had to be recalibrated therefore some of the samples had to be measured more than once to check that they were correct. However this is not a very significant error. To ensure that the colorimeter was correct I made sure that I used the correct filter, that the cuvette was clean and that I did not touch the clear side of the cuvette. Also I made sure that I regularly recalibrated the cuvette. To improve this I could have used distilled water to calibrate the cuvette so that it was completely clear. This would have improved the reliability by a small amount. In general the reliability of my experiment was very good despite these errors. This is shown by how high my t-test results were. Also my experimental technique was reliable enough for the results that I got to be accurate, so that the conclusions that I drew were correct. Nevertheless I did get some anomalous results these are: Temperature /�C 1 4 7 10 35 92 60 9 8 65 3 80 19 The reasons for these anomalies are that the beetroot pieces, because they are natural, have varying amounts of pigment in, causing differences in the results. Another reason for these anomalies is that the proteins denature at slightly different temperatures, this is why there is more variation in the results at the middle temperatures, when the proteins first start to denature. ?? ?? ?? ?? Vickie Hayton 12 FRE ...read more.

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