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Investigate the effect of changing substrate concentration on the rate of the reaction between catalase and hydrogen peroxide.

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Introduction

Aim : To investigate the effect of changing substrate concentration on the rate of the reaction between catalase and hydrogen peroxide. Introduction : Enzymes are proteins and biological catalysts, produced by living things. They have high specificity, i.e., they only catalyse one particular reaction; every biological process has its own enzyme designed specially for it. Enzymes are not changed when they perform their function, which means that the enzyme molecule can be used over and over again. Each enzyme has a unique shape. The active site of an enzyme is the region where it fixes itself with the reactant. The reactant on which the enzyme acts is called the substrate. This is why an enzyme's profile is so important; it can only work if the shape of its active site is perfectly correct to interact with the substrate. This is called the lock and key mechanism. Hydrogen peroxide is a by-product formed during metabolic reactions in cells. It is a toxic and has to be gotten rid of as quickly as possible. For this, catalase is a tremendously useful enzyme. Catalase is present in every living cell of the human body. It carries out a very vital reaction :- Hydrogen peroxide Water + Oxygen 2H2O2 H2O + O2 For this particular reaction, catalase can be obtained from potatoes, which may be added to the hydrogen peroxide. The rate of reaction can be calculated very effectively by measuring the amount of oxygen that gets produced. A simple and accurate method of doing this would be to count the number of oxygen bubbles produced during a set time in the reaction. Key Factors : Enzyme activity is mainly affected by temperature and pH value. At high temperatures and extremes of pH, an enzyme changes shape and can no longer work. This is called denaturing. They discontinue working because the shape of the enzyme molecule changes and so does the shape of the active site. ...read more.

Middle

Set aside. (3) To prepare the above setup, fill in a beaker with water from a tap or a bowl previously filled with water at room temperature. The level of water should be such that the test tube can be submerged in it, without it having to overflow. (4) Fill up another beaker with water from the same source and then fill a measuring cylinder with the water from the beaker. Invert the cylinder immediately into the beaker, allowing no water to escape or overflow from the vessel. (5) Insert one end of the rubber tubing into the measuring cylinder, making sure that no water escapes. The other end of the tubing should be attached to the rubber cork that will be used to plug the boiling tube during the course of the reaction. (6) Clamp the required boiling tube onto the extension from the stand and immerse into the relative beaker. (7) In a measuring cylinder, measure out the required quantity of hydrogen peroxide. (8) Pour out the volume of water needed to dilute the hydrogen peroxide, in another measuring cylinder. Do not use the same measuring cylinder for the hydrogen peroxide and water as it will cause pre-integration of both substances. (9) Dilute the hydrogen peroxide in the boiling tube. (10) Add the potato to the test tube and plug the tube instantaneously. Start the timing with this addition. (11) Observe how not much change occurs during the first 30 seconds of the reaction. Hence, do not record any changes that do occur. (12) After the first 30 seconds, record the production of oxygen bubbles on the upper surface of water in the inverted measuring cylinder. (13) Count the number of bubbles created for one minute. This is because, when the production of oxygen first begins, it is slow. Soon, the bubbles start increasing in number rapidly and over a minute, it can become difficult to get an accurate calculation. ...read more.

Conclusion

To extend this reconnaissance, I would first and foremost, choose to explore a wider range of concentrations. This would give me a broader view of the processes that take place during the course of the reaction and get me a more extensive array of results. I would also prefer to undertake a separate option for acquiring results as counting bubbles of oxygen turned out to be a rather chancy procedure. There may even be better source for obtaining the catalase. Cutting up the potato, weighing it, mashing it and then transferring it to the boiling tube, took very long. In this process, a certain amount of potato was lost so that the amount we carried out the reaction with was not the same 2 grams we began with. Catalase is also present in liver and this could be a substitute for potato in a further task. If this is done, it will also help us in comparing the amount of catalase in potato and liver and judge which one would be a better ingredient for an appropriate enzyme concentration. If I had to do this research again with a different method, I would, most importantly, use different apparatus. Firstly, I would use a gas syringe to measure the amount of oxygen being produced, instead of just counting bubbles, which in my opinion, did not prove to be very accurate. This may also prevent further hassle with the rubber tubing. Furthermore, I feel that the experiment will be more successful if carried out at the optimum temperature of catalase. In this way, the reaction rate will not be limited by low temperature. As a final point, I feel that extending the investigation would generate better results because it would give me a chance to view better circumstances for the experiment to be carried out in, as well as to explore, in depth, the reason for all the anomalies and atypical ingredients of this initial research. ...read more.

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