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An investigation into the rate of reaction of the enzyme urease.

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An investigation into the rate of reaction of the enzyme urease Introduction Enzymes are protein molecules produced in living cells. They act as biological catalysts. They are specific to certain reactions, and so they only operate within narrow temperature and pH ranges. Urease is an enzyme that breaks the carbon-nitrogen bond of urea to form ammonia and carbon dioxide. This can be represented in the equation: Urea urease ammonia + carbon dioxide (NH2)2CO urease NH3 + CO2 The rate of reaction of the enzyme can be affected by the following variables: a) pH: at too high pH, the enzyme is denatured due to the loss of H+ ions. The same applies for too low a pH level, where too many H+ ions would attach to the negative regions of the enzyme, changes its shape and causing it to denature. b) Concentration of enzyme: The higher the concentration, the higher the rate of reaction will be. With a larger number of urease molecules, the chance of successful collisions between enzyme (urease) and substrate (urea) will be increased. This is the factor which I will be investigating in my experiment. c) Surface area: Again, the greater the surface area, the greater the rate of reaction will be. So with a larger surface area, there is more chance of successful collisions between the urea and the urease taking place. d) Temperature: An increase in temperature will speed up the rate of reaction because the reacting molecules have more kinetic energy, so more collisions are likely to take place. ...read more.


0.00348 1.5 1.5 5 2 431 0.5 21 0.00232 1 2 5 2 761 0.3� 21 0.00131 Experiment 3 Amount of Amount of Amount of Amount of Time taken to Concentration of Temperature Rate of 1 Urease cm� water cm� Urea cm� Acid cm� reach pH8 (s) Urease (mols) of solution �C reaction time 3 0 5 2 237 1 20 0.00422 2.5 0.5 5 2 263 0.83� 20 0.00380 2 1 5 2 389 0.6� 21 0.00257 1.5 1.5 5 2 435 0.5 21 0.00230 1 2 5 2 737 0.3� 21 0.00136 Analysis After collecting my information, I originally drew graphs plotting the concentration of the urease against the time taken for the reaction to take place. However, these graphs did not show me the rate of reaction of the experiment, which is what I am investigating, so I calculated the rate of reaction using the equation: rate of reaction = 1 time Using these results (see Obtaining Evidence) I was then able to draw graphs plotting rate of reaction against concentration of urease to show how the two are related. As we can see from the graph for experiment 1, the rate of reaction increases as the concentration of the urease is increased. As the rate of reaction increases, it does so proportionally. The line of best fit is straight and there are no anomalous results plotted in this graph. ...read more.


I feel my results are accurate as I have repeated each experiment a total of three times, and almost all the results, apart from the aforementioned anomalies, are around the same figure. To increase the accuracy and to make my results and final conclusion more reliable, I have taken the average result for each concentration from all three experiments. This has ensured that the results I have collected are as accurate as possible and allows me to see the common trend forming. I think my experiment has been successful because the results I have collected clearly support my prediction, and as they have turned out the same each time, are reliable. A downfall of the method is the fact that there is no actual way of telling the reaction has finished, so you have to guess when the solution is around the colour the experiment was stopped at for the last experiment. This is what I think has led to some inaccuracy within my results, because I had to estimate when the solution was the right pH. This experiment could be improved in a number of ways. I feel I have repeated my results enough times to achieve accurate results, but by using more concentrations of urease I would have produced a more accurate graph which would support my results further. I could have used concentrations higher than the concentration I started with, so that I could see how the rate changes through a greater range and to see if the maximum possible rate of reaction could be reached. ...read more.

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