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Investigate the effect of temperature on the activity of catalase (from potato)

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Introduction

Arefin Khan The Effect of Temperature on Catalase Enzyme Aim: Investigate the effect of temperature on the activity of catalase (from potato). Introduction: Enzymes are biological catalysts. They speed up metabolic reactions in the body but remain chemically unchanged themselves. Enzymes contain an active site. This is a region, normally a depression or cleft, to which another molecule may bind. This molecule is known as the substrate, and is usually specific to the active site of the particular enzyme, which breaks it down. Substrates will not usually fit into any other active sites other than that of the enzyme it is specified to. This can be explained as a lock and key model, where the lock and key are specific to each other, only, that there are many of the same kinds of lock and key when it come to the enzymes. Just as lock and keys have three-dimensional shapes, proteins are also three-dimensional. Usually, there is only one active site on an enzyme; however there can be more. Some energy releasing reactions in cells produce hydrogen peroxide. This is acidic, and can thus, kill cells. Normally, hydrogen peroxide decomposes to form hydrogen and oxygen: 2H2O2 2H2O + O2 However, this process is very lengthy. There is an enzyme known as catalase in cells which dramatically increases the rate of decomposition of hydrogen peroxide. catalase 2H2O2 2H2O + O2 This type of reaction where a molecule is broken down into smaller pieces is known as a catabolic reaction. In order to investigate the effect of temperature on the activity of catalase, I will record the amount of oxygen released when hydrogen peroxide is broken down. Variables: There are quite a few variables which can alter the rate of reaction, and need to be kept constant. They are as follows: a) PH: at too high PH, the enzyme is denatured due to the loss of H+ ions. ...read more.

Middle

Goggles Cutting tile Clamp and stand Beaker (250cm3) Graduated pipette (5ml) ice Thermometer (0 �C-100 �C) Arefin Khan During the experiment, the apparatus will be set up in the way shown below: During preliminary work, I found that the 100 cm3 measuring cylinder was ideal for the measurement of water being displaced by oxygen formed during the reaction. This is because it is graduated in millilitres. Thus, it will be possible to measure the displacement of water to the nearest 0.5 of a millilitre. Also, the measuring cylinder is not so small that the volume of oxygen produced will be greater than the cylinder can hold within the course of the reaction. The 50cm3 measuring cylinder used to measure the volume of hydrogen peroxide was ideal as the amount of hydrogen peroxide was wasn't too little that it would be inappropriate and also inaccurate to measure with a 50cm3 measuring cylinder, nor was it so large, that it would just about be measured. Boiling tubes are ideal for the reaction to take place in, as the volume of oxygen produced is quite small. Thus, it will be quicker for the oxygen produced to be able to displace the water in the measuring cylinder. With a conical flask, it would take much longer. I also found that the breakdown of hydrogen peroxide at room temperature is very slow (Without a catalyst). No oxygen was given off at all over the period of time I observed the hydrogen peroxide for any reaction. However, I did not test whether this was true for higher temperatures. If it was not, then there is the likelihood of major inaccuracies in the conducting of the experiment. Arefin Khan Source: Background information used during this investigation was obtained from Cambridge Advanced Sciences. Biology 1 - endorsed by OCR: Chapter 3. (Page 42 onwards.) Also, information on variables was taken from concepts learned in AS chemistry: (Salters Horners Advanced Chemistry) ...read more.

Conclusion

d) PH level may have altered If I was to conduct the experiment again, I would make sure that it was more accurate overall. This would ensure that the results obtained were more reliable and accurate. I would do this in the following ways: 1) I would use a graduated syringe, instead of a measuring cylinder as this would ensure that it was easier to measure the volume of oxygen produced. It would also be more accurate as there would be a clear line to mark the amount of oxygen produced and there would not be a need to observe where thw meniscus of water touched on the graduation marks. 2) I would use a greater volume of water to ensure that the temperature of the reactants remained constant, due to the fact that water is such that, the greater the volume, the greater its ability to retain heat. 3) I would use a buffer to control the PH of the reactants as it would ensure that the Ph remained constant. 4) I would crush the potato to a paste, using a mortar ant pestle, and drain the filtrate for use as the catalase sample. A measure of the volume would be made.In this way, the exact amounts of enzyme could be calculated. If not, then I would use yeast as my enzyme, as it can be measured out to very precise quantities. 5) I would also use a graduated syringe to measure out the amounts of hydrogen peroxide, and other fluids. The reasons for this are the same as the ones mentioned above. With the above taken into account, I would say that my conclusion is in fact, not very safe due to the fact that there were too many errors and uncertainties concerning the results obtained. Subsequently, the results do not provide a very stable evidence for support of my hypothesis. Although the percentage error of individual equipment may have been at first glance, small, they add up to large percentage errors which then render useless, the legitimacy of the results obtained. Suma_83@hotmail ...read more.

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