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What factors affect the activity of urease? What are the kinetics of the urea-urease reaction?

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Introduction

Chemistry Coursework What factors affect the activity of urease? What are the kinetics of the urea-urease reaction? Aim: To investigate closely the factors that can affect the activity of urease. The effect of concentration and temperature can be studied over a period of time leading to the order and activation enthalpy of the reaction. Introduction: UREASE (NH2)2CO + 3H2O ----------> 2NH3 (aq) + CO2 (g) Urease is an enzyme found in microorganisms, invertebrates, and higher plants. It catalyses the hydrolysis of urea to ammonia and carbon dioxide. In some bacteria and invertebrates this reaction is the final step in the breakdown of complex nitrogenous compounds before ammonia is excreted. Method: Quench with known volume and concentration of HCl to stop the reaction. Some of the acid will react with the ammonia produced by Urease to determine the amount of HCl used up. Contents of the flask are titrated with standard Sodium Carbonate solution using methyl orange indicator. From the results of this titration, the amount of HCl that did not react with the ammonia can be found by substituting the amount of HCl used to neutralise ammonia can be found. Background Knowledge: An enzyme, such as Urease, is a protein that acts as a catalyst, speeding up the rate at which a biochemical reaction proceeds but not altering the direction or nature of the reaction. An enzyme catalyses virtually every metabolic reaction that takes place within a living organism. Enzyme molecules have a special feature in that they possess an active site. The active site is a region to which another molecule or molecules can bind. This molecule is the substrate of the enzyme. The shape of the active site allows the substrate to fit perfectly and to be held in place by temporary bonds, which form between the substrate and some of the R groups of the enzyme's amino acids. This combined structure is termed the enzyme-substrate complex. Each type of enzyme will usually act on only one type of substrate molecule. ...read more.

Middle

Therefore, it is fair to say that the exact temperature would have been roughly +/- 2�C of this value. I then placed the heated solution into a beaker containing my measured 80cm3 of Urea. I immediately started the stopwatch when both reactants reacted. Once again every minute I took a sample of 10ml of this solution using a bulb pipette and placed it in a conical flask containing my 50ml of 1M Hydrochloric acid. I will then add a few drops of methyl orange indicator to the solution. Finally, I will titrate my 0.5M solution of Sodium Carbonate and will turn the tap off the burette at the first sign of colour change. The volume of alkali added will be recorded. I will each temperature three times over. I will carry out the same procedure for each experiment, except for the 10�C, as I will have to add ice to the urease solution to cool it down. Diagram of Experimental Procedure Prediction: I predict that as both the temperature and the concentration increase then so does the rate of the reaction increase. As the temperature increases, molecules have more kinetic energy (vibrate more often per second) with which to react. They collide more often and are more likely to collide with enough energy to overcome the activation energy needed. This is the energy that is needed to start breaking the bonds in the colliding molecules so that the collision can lead to a reaction. Figure 4 in Chemical Ideas page 224 shows that when you increase the temperature by 10�C, from 300K to 310K. E.g. The activation enthalpy of a reaction is +50kJ mol-1. Figure 5 (Chemical Ideas, pg. 225) shows the number of collisions with energy greater than 50kJ mol-1, for the reaction at 300K. It's given by the shaded area underneath the curve. However, the optimum temperature at which most enzymes work is approximately 40�C or roughly body temperature and I believe this to be true for Urease also. ...read more.

Conclusion

Vol. of added Na2CO3 (VT) in cm3 V0-VT (50-VT) in cm3 1 45.3 4.7 2 38.6 11.4 3 35.9 14.1 4 20.4 29.6 5 15.1 34.9 0.25M Urea Time (mins) Vol. of added in Na2CO3 (VT) in cm3 V0-VT (50-VT) in cm3 1 36.8 13.2 2 26.4 23.6 3 18.5 31.5 4 14.4 35.6 5 12.8 37.2 0.4M Urea Time (mins) Vol. of added in Na2CO3 (VT) in cm3 V0-VT (50-VT) in cm3 1 27.0 23.0 2 16.8 33.2 3 11.9 38.1 4 8.8 41.2 5 7.1 42.9 0.6M Urea Time (mins) Vol. of added in Na2CO3 (VT) in cm3 V0-VT (50-VT) in cm3 1 22.2 27.8 2 11.6 38.4 3 7.9 42.1 4 3.7 46.3 5 2.4 47.6 1.0M Urea Time (mins) Vol. of added in Na2CO3 (VT) in cm3 V0-VT (50-VT) in cm3 1 10.3 39.7 2 3.2 46.8 3 2.8 47.2 4 2.4 47.6 5 2.1 47.9 1M Urea - Varying Urease Urease concentration (%) Volume Na2CO3 titrated at the end of 5mins in cm3 V0-VT (50-VT) in cm3 1% 0.40 49.60 0.7% 8.35 41.65 0.5% 12.40 37.60 0.2% 27.40 22.60 0.1% 39.70 10.30 1% Urease Time (mins) Volume Na2CO3 titrated at the end of 5mins in cm3 V0-VT (50-VT) in cm3 1 12.20 37.80 2 3.90 46.10 3 1.80 48.20 4 0.75 49.25 5 0.40 49.60 0.7% Urease Time (mins) Volume Na2CO3 titrated at the end of 5mins in cm3 V0-VT (50-VT) in cm3 1 33.90 16.10 2 14.35 25.65 3 17.00 33.00 4 12.10 37.90 5 8.35 41.65 0.5% Urease Time (mins) Volume Na2CO3 titrated at the end of 5mins in cm3 V0-VT (50-VT) in cm3 1 38.50 11.50 2 29.45 20.55 3 21.75 28.25 4 15.95 34.05 5 12.40 37.60 0.2% Urease Time (mins) Volume Na2CO3 titrated at the end of 5mins in cm3 V0-VT (50-VT) in cm3 1 43.30 6.70 2 37.45 12.55 3 32.50 17.50 4 29.05 20.95 5 27.40 22.60 0.1% Urease Time (mins) Volume Na2CO3 titrated at the end of 5mins in cm3 V0-VT (50-VT) in cm3 1 48.15 1.85 2 45.50 4.50 3 43.05 6.95 4 41.10 8.90 5 39.70 10. ...read more.

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