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Biology coursework

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Investigating the effect of bead diameter on conversion of sucrose to glucose and fructose by immobilized invertase Hypothesis- I predict that as the invertase beads decrease in diameter, the rate of glucose production will increase. Background Biology Enzymes are protein molecules, which serve to accelerate the chemical reactions of living cells. Without enzymes, most biochemical reactions would be too slow to even carry out life processes. Enzymes display great specificity and are not permanently modified by their participation in reactions. Since they are not changed during the reactions, it is cost-effective to use them more than once. However, if the enzymes are in solution with the reactants and/or products it is difficult to separate them. Therefore, if they can be attached to the reactor in some way, they can be used again after the products have been removed. Specificity Enzymes are usually very specific as to which reactions they catalyze and the substrates that are involved in these reactions. Complementary shape, charge and hydrophilic/hydrophobic characteristics of enzymes and substrates are responsible for this specificity, which is often referred to as "the lock and key" model. Immobilized enzymes An immobilized enzyme is an enzyme that is physically attached to a solid support over which a substrate is passed and converted to product. There are a number of advantages to attaching enzymes to a solid support and a few of the major reasons are listed below: * Multiple or repetitive use of a single batch of enzymes * The ability to stop the reaction rapidly by removing the enzyme from the reaction solution (or vice versa) * Speedy separation of products reduces feedback inhibition * Product is not contaminated with the enzyme (especially useful in the food and pharmaceutical industries) * Analytical purposes - long 1/2-life, predictable decay rates and elimination of reagent preparation * Thermal stability is increased allowing higher temperatures to be used * Higher operating temperatures increase rate of reaction When immobilizing an enzyme to a surface, it is most important to ...read more.


The reason I have chosen to use 17 minutes is that after preliminary trialling, I discovered this was the ideal time to leave the beads to harden and that they would produce the best results after this time. * I will ensure that I use the same beaker, measuring cylinder and pipette dimensions throughout my experiment. Although I could use many instruments to take measurements, I will always use the same ones to make sure that the experiment is fair. * I will always be using the same brand of Diabur 5000 test strips to measure how much glucose there is in the bead and sucrose mixture and I will always take down the results in mmol/litre as this will produce the most creditable results. * I will also make sure that the test strips are used every 30 seconds for 5 minutes with every bead size as this will ensure the results are fair. I will time the reaction using a stop clock, taking readings every 30 seconds without pausing the stop clock for any reason. * I will always mix the chemicals such that the sodium alginate will always go into the beaker before the invertase and they will always be stirred with a glad rod to ensure equal distribution. * I will always measure 10 beads of each size, using the micrometer as this will help me to work out a sensible average. It will also make the experiment more fair and plausible because the results will not be based on only one bead coming from each nozzle as even beads from the same nozzle may very considerably in size. * Finally, I will make sure that all the glassware, measuring cylinders, pipettes, nozzles, syringes, strainer and glass rod are thoroughly washed with tap water and then distilled water each time I use them. Risk Assessment Calcium Salts Calcium Chloride Calcium chloride is an irritant; wear goggles to protect eyes; avoid inhalation and raising dust. ...read more.


The 210mm is also shown on the next page. Another important factor is the various limitations involved in drawing a conclusion from a single investigation. The use of 5 different nozzle sizes, though perhaps sufficient for my investigation, is not sufficient for drawing a firm conclusion. This is because a lack of further investigation prevents the more extensive results, which would be required in order to assert a conclusion. Overall it would appear that my investigation does support my hypothesis that as the beads decrease in size, the rate of reaction will increase. In regard to further work, I would need far more different nozzles of distinguishably different diameters in order to come to a definite conclusion. In addition, carrying out more repeat tests would help ensure the experiment was more reliable and this may lead to a better end result. I also faced a problem in that the colours shown on the Diabur test strips are of course limited and I had to assume the colour according to the scale I had. However, it might have been a good idea to decide on a value for colours in between the values I was given. This may have made the data more reliable as well as providing a higher degree of accuracy. Finally, I could have used pH buffers in order to ensure the pH of every solution was exactly the same. This would have made the test more fair and perhaps given more accurate results. For this particular investigation I used yeast-derived invertase but had more time been available, it would have also been profitable to investigate a wider range of invertase enzymes, perhaps derived from different sources. Furthermore, I used the method of immobilizing the enzymes by entrapping them within a gel to form the sodium alginate beads. However, there are a variety of other ways I could have done this: * Carrier-Binding: the binding of enzymes to water-insoluble carriers * Cross-Linking: intermolecular cross-linking of enzymes by bi-functional or multi-functional reagents. * Covalent bonding to a solid support * Encapsulation behind a selectively permeable membrane ...read more.

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