Testing Artificial Urine Samples

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Testing Artificial Urine Samples


The aim of the experiment is to find out the concentration of urea in the unknown urea solution.


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


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.


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...
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