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Effects of Copper Sulphate on the Activity of Catalase

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Introduction

Effects of Copper Sulphate on the Activity of Catalase Introduction Enzymes are biological catalysts and their contribution to our existence is pivotal. Without them, human and animal digestion may take days. Enzymes therefore, help catalyse reactions at an increased metabolic rate. Each type of enzyme would normally act upon only one type of substrate molecule. This is due to the specific shape of the active site. Sometimes, enzyme activity is disrupted not because of temperature or other environmental factor but by alien molecules, which attach themselves to the enzyme molecules just as easily as the intended substrate. This is called inhibition. Aim I will be testing the effects of Copper Sulphate (inhibitor) on a reaction between catalase and hydrogen peroxide. I predict that the greater the concentration of the copper sulphate, the slower the reaction. Reactions will be measured at the rate of which oxygen is released from the H2O2. I will use yeast as a source of the enzyme catalase. If it is an inhibitor, I will go further and try to prove if it is a competitive or non-competitive by increasing substrate concentrations. Fig 1 shows word equation of the reaction. 2H2O2 2H2O + O2 Figure 1 Scientific Involvement At a molecule level, it is thought that the substrate molecules fit precisely into the enzyme molecules in the same way that a key fits a lock (see Fig 2). The part of the enzyme molecule into which the substrate fits is called the active site. Figure 2 The configuration of the enzyme molecule is due to ionic bonding, hydrogen bonding, disulphide bridges and hydrophobic interactions I know that enzymes have optimum temperatures and optimum pH levels. The enzyme is said to denature at temperatures exceeding its optimum or at the wrong pH level resulting in an ineffective enzyme molecule (Fig 3a). Inhibitors that compete for the active site are called competitive inhibitors. ...read more.

Middle

The rate at which the water level falls can be taken as the rate of oxygen produced. This method guarantees that no oxygen will be lost at any stage. I will be doing two tests. One to show the normal rate of reaction between 2%catalase and various concentrations of 3%hydrogen peroxide and the second will be the same but with One ml of 0.5M copper sulphate added to it. The two different results will allow me to make a comparison and will also allow me to conclude whether copper sulphate is an inhibitor of catalase or not. And testing it with various concentrations will show me if it is a competitive or non-competitive inhibitor. Dilution Table: Test tube 1 Test tube 2 Test tube 3 Test tube 4 Test tube 5 H2O2 20 vol (ml) 5 4 3 2 1 Water (ml) 0 1 2 3 4 Final Volume (ml) 5 5 5 5 5 Final Concentration (%) 100 80 60 40 20 Final Concentration (vol) 20 16 12 8 4 Safety * Enzyme inhibitors are metabolic poisons harmful to all forms of life. They must be handled with care. * Any small volumes of the inhibitor must be measured out using a syringe; safety spectacles must be worn. * Aprons or some other form of protective clothing must be worn because the H2O2 is known to bleach most things it comes in contact with. * Enzyme preparations containing added inhibitors should be in labelled tubes * When the experiment is completed, dispose of mixtures with excess water and rinse out the tubes before setting them aside for washing. * Otherwise good laboratory practice is sufficient to take account of any hazards and avoid significant risks Bibliography * Toole, G. & Toole, S. 'A Level Biology' Letts Educational (1999) * Jones, M., Fosberry, R. & Taylor, D. 'Biology 1' Cambridge University Press (2001) * www.seps.org Results The amount of oxygen produced (ml) ...read more.

Conclusion

It was actually my ability to read values and faulty apparatus that lead to errors rather than my method. In my opinion it was ideal for producing such reliable results. My method have limitations because I didn't try for a continue to record values until the reaction had stopped completely. I also should have done some experimenting with solutions of more than a 100% concentration to further support that CuSO4 is non-competitive inhibitor. Testing with more concentrations may even surprise me with a shock increase in the rate of reaction, if this does not occur then eventually excess substrate inhibition should take place and reduce the rate of reaction to zero. The results are satisfying because they represent my prediction and most importantly they represent what is known to happen when CuSO4 is introduced to a catalase and H2O2 reaction. This makes my results very reliable and it poses as firm evidence that proves CuSO4 is a non-competitive inhibitor of catalase. The use of a gas syringe would help make the results more reliable because I will be less concerned with resetting the equipment, meaning more time would be spent on attempting to acquire more accurate results. Thus avoiding any anomalous results at all. The gas syringe is designed for collecting gas and it will always give you the correct reading no matter what position you hold the syringe in. With a measuring cylinder, you have to keep it straight because the slight tilt will make the meniscus appear to be at one value on one side and a different value on the other. I don't have enough anomalous results to make my conclusion invalid, the few that I do have are very minor anyway. All the anomalous results are eliminated when a line of best fit is drawn on the rate of reaction graph, which shows a trend of the completely reliable results. Abdus Salam A/S Biology Coursework Page 1 of 7 ...read more.

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