Introduction One function of the kidneys is to regulate the concentration of urea in urine. In this experiment the enzyme urease acts as a biological catalyst and speeds up the reaction rate. The urease breaks down the urea and produces carbon dioxide and ammonia [pic] The six boiling tubes contain urea, agar gel and a pH indicator. The gels inside the boiling tubes contain bromothymol blue which gives it its yellow colouring and each tube has been acidified with citric acid.
Once the enzyme urease has been added to the boiling tubes and left for 24 hours the agar gel will turn blue in colour indicating the production of ammonia from the breakdown of urea. The measurement taken from the blue gel inside the boiling will determine the amount of ammonia produced. Equipment and Materials The equipment used in this experiment consists of; 6 boiling tubes containing acidified sugar with bromothymol blue indicator, six stoppers for the boiling tubes, 7x2cm3 syringes, urea solutions (prepared in advance).
The urea concentration within the solutions are (mMol) 31. 5, 62. 5, 125, 250, 500. The equipment also contained an urea solution with an unknown concentration and urease solution. Method First 2cm3 of urease was added to each of the six test tubes which contained the acidified agar (using one of the seven syringes) then using the remaining syringes 2cm3 of the urea was added to five of the boiling tubes, each boiling tube getting a different concentration of urea added to it using a clean syringe each time.
2cm3 of the unknown concentration of urea was then added to the sixth boiling tube. The stoppers were put into the boiling tubes and they were left in the same room for 24 hours. After 24 hours the length of the blue agar was measured and the results recorded in the table of results below and plotted on a line graph (see attached graph sheet). Table of Results |Concentration of urea solution (mMol) |Class Results (mm) |Mean Average (mm)| |500 |25 26 27 27 / 29 29 21 28 |26. 5 | |250 |21 22 20 21 21 21 22 20 25 |21.
4 | |125 |14 16 15 15 18 15 17 15 14 |15. 8 | |62. 5 |8 5 4 8 10 6 10 9 10 |7. 8 | |31. 2 |2 1 2 2 0. 1 1 5 1 2 |1. 8 | |Unknown |14 15 13 15 15 13 18 11 12 |14 | Conclusion From the graph drawn on the graph sheet it can be concluded that that the unknown urea concentration is 110 mMol. Discussion or results Within this experiment there are numerous variables that were kept constant and controlled to ensure accurate results. The variables include the volume of agar gel, the volume of urease solution, and the volume of the pH indicator.
The temperature and length of time the boiling tubes were left in the room (before measurements were taken) were other important variables to be considered and kept constant during the experiment. A variable that was not kept constant was the concentration of urea going into the boiling tubes. The reason for this was to examine and record the ammonia produced from different concentrations of urea and to use these results to find out the unknown urea solution’s concentration.
As a precaution and to ensure accurate results contamination of urea solutions was avoided by using a clean syringe for each concentration of urea. A clean syringe was used for the measurement of the urease to avoid cross contamination between the urease and urea solutions. The same method of measuring the urea solution was used to ensure the accuracy of the experiments results. A more accurate and reliable result was provided by taking a class mean average of the experiments results (as detailed in the table of results on the previous page. )