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How varying the substrate concentration (hydrogen peroxide) when reacting with an enzyme catalyse (potato) affects the volume of oxygen produced.

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Enzymes are biological catalysts. They increase the rate of chemical reactions taking place within and around living cells without suffering any overall change. There are 3 known factors that affect the rate of reaction in accordance with predictable interactions between enzyme and substrate molecules: Temperature - The affects of temperature may be explained on the basis of kinetic theory. Increased temperature increases the speed of molecular movement and thus the chances of molecular collisions. It is often said that an enzyme's rate of reaction doubles for every 10� C rise in temperature. pH - Changes in the pH affect the attraction between the substrate and enzyme, and thus the efficiency of the conversion process. Often there is an optimum pH, near pH 7 (neutral) in intracellular enzymes, and in the acidic range between pH 1-6 and in the alkaline ranges between pH 8-14. Concentration - There are two types of concentration, concentration of substrate and concentration of enzyme. Substrate concentration can alter the rate of reaction as the higher concentration the more frequent collisions with enzymes and therefore a higher rate of reaction. The concentration of enzymes is similar, as if there is a higher concentration of enzymes then there will be more frequent collisions and therefore a faster rate of reaction. AIM: How varying the substrate concentration (hydrogen peroxide) when reacting with an enzyme catalyse (potato) affects the volume of oxygen produced. BACKGROUND KNOWLEDGE: The reactants of enzyme-catalysed reactions are termed substrates and each enzyme is quite specific in character with a unique 3 dimensional shape shared by all its molecules. Within the shape there is an area called the active site where the chemical reactions occur. In order for this reaction to occur only a small amount of enzyme (catalyse) added to the substrate is required. As according to the Lock and Key theory, the substrate and catalyse molecules are continuously on the move and providing that the substrate is complementary to the active site of the enzyme, every so often they will collide so the substrate molecule(s) ...read more.


7. Repeat stages 3-6 again, but stage 3 should be altered so the next range of substrate concentration is experimented. i: this procedure should continue until you have recorded all results up to 50 cm3 water and 0 cm3 hydrogen peroxide. 8. Finally repeat the whole experiment again in order to increase the accuracy of results which will make an average calculation possible for each recording. Before the results are recorded into the final results table, initially this should be converted to the volume of oxygen collected. This can be calculated from simply subtracting the volume of water present in the measuring cylinder after 5 minutes from the volume of water at the beginning of the experiment. There are many elements to ensure a fair test is carried out: All recordings will be repeated twice; this will allow me to identify any recording that doesn't follow the usual trend and furthermore calculate an average, I will use the same set of equipment for each recording, and caution will need to be taken when measuring the volume, as a mere mismatch of measurement may be unreliable. Safety is also a major factor that needs to be kept in mind at all times: Risk Preventative Actions Hydrogen Peroxide irritant Wear goggles, Care when dispensing, Mop up spillages, wash of spillages quickly. Tube breakages Wear goggles; clear up immediately after breakage occurs. All apparatus should be handled with care, and primarily with the glass equipment placed away from the edge of the desk. RESULTS: Length of potato chips - 3cm Temperature - Room temperature VOLUME OF WATER (CM3) CONCENTRATION OF HYDROGEN PEROXIDE (CM3) VOLUME OF OXYGEN COLLECTED (CM3) IN 5 MINUTES -1dp- 1 2 Average 0 50 12.5 12 12.25 10 40 11 11.5 11.25 20 30 10 8 9 30 20 8 7.5 7.75 40 10 5.5 5.5 5.5 50 0 0 0 0 The lengths of the magnesium were all matching in length, and I assured the concentration of hydrogen peroxide used was as precise as possible to the required measurement. ...read more.


This enabled me to calculate an average and gave me the advantage of being able to produce a better analysis overall. In addition to the scopes of errors mentioned above, there are many other incontrollable factors that may have had a form of influence or obstruction. However no significant problems or difficulties were encountered whilst conducting the experiment. My results and conclusion were accurate and reliable enough to verify a relationship that as the concentration of hydrogen peroxide is increased, the rate of reaction also increases, hence agreeing with my set prediction. Improvements: No matter how accurate produced results are, due to the restriction in apparatus provided and the time to complete the investigation, improvements will always be applicable. Possible improvements: * There are methods to ensure the temperature is kept constant throughout the experiment. This could be by adding ice whenever the temperature exceeds the normal room temperature; however it is known that the most productive temperature for enzymes to work is at about 40�C. So therefore the temperature could be kept at this constant with the use of a thermometer, Bunsen burner or kettle. * Instead of simply measuring the length of the potato pieces it would be more accurate if they were weighed also. This would be to ensure the pieces are indistinguishable. * Even though two repeats for each recording was accurate enough to produce a reliable average, increasing this to three or four recordings would produce a range of results which could then be analysed in more detail. Extending the investigation: * There are alternatives to using a potato for catalyse for example cheese or bread. A liquid can also be used, yoghurt, beer or wine to name a few examples. * It would be interesting to observe the results if the concentration of hydrogen peroxide was varied to every 5cm3. * The affect temperature has on the rate of reaction can be investigated by making this the independent variable and making the concentration a constant. SECONDARY SOURCES OF INFORMATION: http://www.8886.co.uk http://www.s-cool.co.uk http://homepage.ntlworld.com/mbradley49/science/amylase_project.html NIKESH PARMAR - 11E 1 ...read more.

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