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An investigation to establish how concentration of substrate effects the rate of anaerobic respiration of yeast.

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Simon May 13I Biology Coursework An investigation to establish how concentration of substrate effects the rate of anaerobic respiration of yeast Aim The aim of this investigation is to produce data from which an accurate evaluation can be formed which shall show in quantitative terms how the anaerobic respiration of yeast occurs when the substrate concentration alters. Preliminary Research From my preliminary investigations I was able to deduct which of numerous methods stood the best chance of offering success in terms of giving quantitative data that was both accurate and reliable. In addition to this I was able to investigate which solutions offered the most activity and which range was most appropriate to the investigation. From these, investigations I have concluded the following: 1. Methods 1 and 2 outlined in the planning section offered the best chance of accurate, reliable, safe and easily reproduced data. 2. The substrate to be used in terms of producing accurate data does not really matter in terms of whether orange Juice or Glucose is used. However, Orange Juice offers the best qualitative data, whereas, the absence of vitamins means that glucose substrate results offer better quantitative data. This, it seems appropriate that both substrates are used in this investigation. 3. Although up to 2moldm-3 of glucose as a substrate gives good results. The optimum maximum concentration is 0.2moldm-3. This is due to the higher concentrations drawing out more of the yeast's water by osmosis to combat the high concentration gradient produced by the substrate compared to the cell interior. In severe cases of high concentration outside the yeast this can lead to the destruction of the yeast itself. For more detailed information of the method selection see A3 sheet enclosed. Method 1: Diagram Below is a diagram of the final experiment and procedure that was developed from my preliminary work: Method To obtain accurate data from this investigation I must ensure that for every experiment that the following method is implemented. ...read more.


Also, temperature can have an adverse effect on the rate of reaction if an enzyme is involved (see variables section). Finally, non-competitive and competitive inhibitors, these have the ability to affect the rate of respiration because if they attach themselves to the active site or any other area of the enzyme they can distort the shape. Thus the ability for the enzyme to work- this can be both on a permanent and temporary affect. The inhibitors work by changing the shape so those substrate molecules cannot fit the desired pattern and be used in the ensuing reaction. Thus, the enzyme is useless. These factors will affect my experiment significantly because the anaerobic respiration of yeast is highly dependent on the enzyme alcohol dehydrogenase. To illustrate these points the following diagrams are enclosed from the resources named in the bibliography section. Safety To complete this investigation in a safe manner for both myself and my colleagues, I must ensure that the following are in use all the time when laboratory work is under way: 1. All substances and containers are labelled and securely stored in the centre of the desk when not needed. 2. All spillage's and breakage's are reported to the appropriate authority in the event of an accident. 3. Throughout this investigation I must ensure that I am always wearing Safety spectacles and that all loose clothing is away from chemicals. 4. Make certain that the yeast Candida Albicans is not present because it may in extreme cases cause Candidasis. Range To obtain accurate and reliable information in this experiment I shall take five different concentrations of sugar and orange juice solution for the yeast to respire. This range will be between 0m and 1m. Accuracy and Reliability To increase the accuracy and reliability of my data in this investigation I shall repeat each experiment three times. The reasoning behind this is that if any anomalous results occur I shall be able to highlight and repeat this data without my results being effected. ...read more.


following alterations: * I would conduct the initial homogenisation of the yeast and substrate in excess amounts of each and then dip in a sample test tube to up turn and do all of this beneath the water. The advantage in terms of accuracy I believe would be significant because the air bubble created in up turning the test tube would be eliminated. Method 2 If the experiment was to be repeated using the apparatus and method specified in "method two" to ensure an improvement in the accuracy and reliability I would make the following adjustments: * The water-bath and bath underneath the burette keeping the water in the burette become one and the same. I believe that this would increase the accuracy because the delivery tube length would be significantly cut. Therefore the loss of pressure also, thus more accurate data could be obtained. Improvements applying to both methods In terms of improvements that would improve the accuracy and reliability of both the experiments I would recommend that the following changes be adopted in future experiments: * Increased range and number of repeats so that we can be more certain of obtained data and the pattern that it is showing. * A device that enables the yeast and substrate to homogenise quicker and the same in each experiment, i.e. something better than just the hand shaking to produce the required mixing and reaction start. * Improved accuracy on measuring devices. This would help improve the accuracy because errors caused by measuring cylinders and other measuring instrumentation for recording data would be greatly reduced. Significance of uncertainties Although my experiments were effected by numerous sources of errors with one result in particular being effected enough to be deemed as anomalous I do not believe that the results on the whole were large enough to be classed as significant. I state this because, both sets of data were over 99% accurate, my data supported my theory and the results were constant in terms of repeats. ...read more.

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