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Investigating the density of blood

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Investigating the density of blood Introduction I will investigate the relative density of three unknown blood samples by measuring the time taken for drops of simulated blood to fall under gravity through a solution of copper II sulphate. By comparing the two samples I can determine the relative density of them compared to the normal sample. There are three separate samples of simulated blood and each one will be tested. 1. Sample 1 will be from a healthy male 2. Sample 2 will be from the same male after 6 months of regular exercise. 3. Sample 3 will be from the same male after suspected blood doping. By analysing the results obtained I should be able to determine the relative density of the blood. Background scientific knowledge and understanding I would expect an average healthy male to contain 5-7 litres of blood. Each drop of blood would contain * 250 million red blood cells * 400,000 white blood cells * and 15 million platelets [JA1]1 Located with the erythrocytes is haemoglobin. Haemoglobin transports oxygen which is used for respiration. The red blood cells transport the haemoglobin so it can be delivered to wherever needed inside the body, however haemoglobin has a relatively small weight for a respiratory pigment. Haemoglobin molecules are able to pick up oxygen where it is plentiful and transport and release it to where energy levels are low in the body. This is important when exercising or playing a sport when you require a lot of extra oxygen. As cells in tissues are respiring more when exercising they are using up more oxygen, this means the concentration of oxygen in these areas will be low. To continue performing well they require more oxygen. The oxygen in the haemoglobin will now find its way to the tissue and will diffuse from the red blood cell, this method keeps a relatively good consistent supply of oxygen. ...read more.


Avoid splashing and contact with eyes and mouth. There is a risk of broken glass if beakers and measuring cylinders are not handled correctly leading to cuts. Handle carefully. [JA6]6 Results My raw data is located in the appendix of my coursework, my processed results are shown below. Blood drop number Sample 1 /s Sample 2 /s Sample 3 /s 1 8.79 7.33 6.03 2 13.44 10.42 5.84 3 9 6.63 6.57 4 8.75 7.62 5.87 5 8.66 9.33 6.26 6 9.36 6.69 6.9 7 14.02 6.88 5.74 8 9.34 8.12 7.69 9 12.36 10.39 6.31 10 8.79 6.98 7.66 Mean 10.251 8.039 6.487 Standard deviation (2 dp) 2.14 1.48 0.72 Standard error 10.25 +/- 1.55 8.03 +/- 1.07 6.49 +/- 0.51 True mean (95%) confidence 8.60 - 11.80 6.96 - 9.10 5.98 - 7.00 Relative densities To compare densities I will assume the relative density of the normal sample is 1.00 The relative density of unknown sample is found by formula, RDsample1 x time sample 1 / time unknown sample. RD sample 1 = 1.00 x 10.25 / 8.03 = 1.28 (28% increase in density over sample 1) RD sample 2 = 1.00 x 10.25 / 6.49 = 1.58 (58% increase in density over sample 1) Tally chart A tally chart helps to decide if the data is normally distributed by plotting a frequency histogram using the chart. The intervals help to show how compact the data is, they are found by dividing the difference between the maximum and minimum values by ten. I have rounded the intervals to the nearest tenth. Key: | represents a count of one / represents a count of five. Speed of drop /s (seconds) Sample 1 total 7.50-8.00<= 8.00-8.50<= 8.50-9.00<= / 5 9.00-10.00<= || 2 10.00-11.00<= 11.50-12.00<= 12.00-12.50<= | 1 12.50-13.00<= 13.00-13.50<= | 1 13.50-14.00<= 14.00-14.50<= | 1 Maximum value 14.02 Minimum value 8.66 Difference = 5.36 Intervals = 5.36 / 10 = 0.536 = 0.5cm intervals Speed of drop /s (seconds) ...read more.


This would eliminate a factor which increases the time taken to travel the distance and would make my results more accurate. > Using a Pasteur pipette means it is very tricky to produce a constant volume of blood droplet. By using a different piece of apparatus it would have been easier to make droplets the same volume. Having the same size droplets eliminates this variable and means my results would be more accurate. An ideal tool for getting a constant volume of the blood would be an automated pipette. > It would have been possible to reduce the parallax error if I had been able to use somebody to stay seated and time the blood droplet to travel the total distance. This person would be dedicated to timing the blood droplet and would not have to worry about releasing the blood droplet. They would just been doing the timing and therefore it is likely that they would have timed more accurately because they would become accustom to where to position themselves to reduce parallax error and because all they would have to do is time the droplet their reaction times would be minimal. > Using the same pipette for every solution means that when you wash the pipette out water stays in the pipette and this dilutes the blood sample when it is taken up. Diluting the blood sample affects the relative density of the blood sample and therefore to avoid this problem in the future I would have used a new pipette for every drop of blood. Validity of conclusion The true means of my samples show some overlap. Blood drop number Sample 1 Sample 2 Sample 3 True mean (95%) confidence 8.60 - 11.80 6.96 - 9.10 5.98 - 7.00 This would suggest that the data is not as valid as it could have been. I think that performing at least 20 measurements for each sample would help to validate my conclusion. ...read more.

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