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Investigation into the density of mock blood.

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. Assessed practical: A2 Practical. Investigation into the density of mock blood. Aim: to find any difference in blood density in the mock blood samples belonging to: * a healthy male living at sea level (a); * the same male after he has undergone 6 months of regular aerobic exercise (b); * the same male who has spent 3 months undergoing aerobic training at altitude (c). Background knowledge: Blood is composed of watery plasma in which a variety of cells are present. The majority of cells present are red blood cells, or erythrocytes. These are red biconcave discs about 7?m in diameter. They have no nucleus, no mitochondria and no endoplasmic reticulum, this is to maximise the amount of oxygen which can be carried by each blood cell. The red colour is caused by the globular protein haemoglobin. The main function of haemoglobin is to transport oxygen from the lungs to respiring tissue. Oxygen is transported around the body in the red blood cells in combination with haemoglobin. Each haemoglobin molecule is made up of four polypeptides each containing one haem group, each of which can combine with one oxygen molecule. Therefore each haemoglobin molecule can combine with four oxygen molecules. This can be represented by the following equation: Hb + 4O2 HbO8 Haemoglobin oxygen oxyhaemoglobin The amount of oxygen which combines with each haemoglobin molecule depends on the partial pressures of oxygen. ...read more.


o Record the results in an appropriate table and repeat the above a further 9 times to gain an average. o Repeat the above procedure with samples B and C, and record the results. Risk assessment: * Goggles must be worn at all times to protect the eyes as you will be handling harmful products throughout the experiment. * Care should be taken when handling copper sulphate as it maybe irritating to eyes and skin. * Care should be taken when handling the syringes as they are sharp objects and can cause injury. * To avoid accidents, wipe any spillages immediately and keep large objects, such as seats, out of the way. Time taken for drop to fall between 100cm3 and 10cm3 (s) Trial no. Solution A Solution B Solution C 1 12.0 13.6 8.4 2 12.3 12.8 7.8 3 13.4 11.8 9.5 4 10.6 10.2 4.3 5 12.1 9.08 6.5 6 12.4 9.9 6.7 7 11.2 12.9 6.8 8 12.2 11.8 8.4 9 11.3 11.9 8.1 10 14.0 13.5 8.9 Total 121.5 118.2 78.7 No.of trials 10 10 10 Mean ? 12.15 11.82 7.87 Analysis and conclusions: The T test is used to test the difference between two unpaired independent samples. This statistical test was used to analyse the data as it is used to test the statistical significance of continuous variables. The mean can be calculated by using the following equation: ? ...read more.


* Human error- reflex actions such as activating and stopping the timer will cause inaccuracies in the results due to hand-eye coordination. Also the size of the drops released through the syringe may vary from trial to trial due to varying pressure applied in the different trials, so this too will affect the final result. * Point at which the drop is released- the height from which the sample is dropped will vary each time due to human error, and also the point from which it is dropped will affect the end result. The way in which the syringe is held will affect the amount of pressure applied which will then have an affect on how much of the sample is released. Modifications: The above sources of error, when considered individually, appear as not having a major influence over the results but if all these errors take place during the experiment then together they are found to be quite significant and can be the major cause of anomalous results. To increase the reliability of the results and in order to gain valid results, these errors will have to be overcome or reduced. The first error mentioned above could be overcome by using a solution that has been prepared by a qualified technician. Working in pairs may reduce human error; by having one person releasing the sample whilst the other activates the timer. Finally by using a clamp stand to hold the syringe in place will ensure a consistent height from which the sample is dropped as well as a consistent position in which the syringe is held. ...read more.

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This is a well researched and detailed report.
1. The background knowledge section needs to be referenced.
2. The analysis of the results is performed well.
3. The conclusion is well detailed.
4. The evaluation shows a good understanding of scientific processes.

Marked by teacher Luke Smithen 05/07/2013

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