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An investigation to determine how excretion of urea is determined by the consumption of protein

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An investigation to determine how excretion of urea is determined by the consumption of protein Urea is formed from excess amino acids present in the body, by the process of deamination in the liver. The amino group is first removed from an amino acid by reacting it with oxygen, giving a keto acid (which can be converted in glucose or fat) and ammonia; the ammonia reacts with carbon dioxide to form urea and water. 2 NH2CH(R)COOH + 2 O2 2 CO(R)COOH + 2 NH3 2 NH3 + CO2 C(NH2) 2O + H2O Ref 1 If the consumption of protein is high, when it is broken down into its simplest form of amino acids by enzymes, the liver will convert the excess amino acids into urea, which is filtered out of the blood in the kidney. Urea is then removed from the body in urine. When urea is in the presence of water and the enzyme urease, a reaction occurs producing ammonium carbonate, a solution with an alkaline pH. ...read more.


The volume of urease added will be in excess to try and ensure that all of the urea is catalysed, and so will always be the same volume. In effort to gain accurate results, I will use 6 different concentrations of urea solution and repeat each test 4 times so that I may take an average result to plot on the graph to give the calibration curve. Because the urea concentration in urine is often in the range of 1.0 to 2.5g per 100cm3, I will use my concentrations at 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0g per 100cm3, to allow for the standard reading and slightly above and below for variation. I will use a test tube of water as a control, to note the end point of the colour change from pink to colourless, so that all the reactions can end at the same point. Apparatus Pipettes Burette Test Tubes Test Tube Rack Water Bath Bungs Droppers Urea solutions Urease Distilled Water Phenolphthalein Hydrochloric Acid Method 1. ...read more.


A human subject known to eat a diet high protein is likely to excrete the most urea, given that he is not growing, or has a irregularly high demand for protein, such as a body builder. The subject can have diets progressively increasing in protein levels, each lasting a week long. In week one, the subject has a diet low in protein, and the urea concentration of the urine is measured at the end of the week. Week two, the protein in the diet is increased, and the urea concentration is again measured at the end of the week. This continues for a period of 1 month, and at the end, the urea concentrations can be compared. I predict that the urea concentration in the urine from week four will be the highest, and week one will be the lowest. This will determine how a change in the consumption of protein in the diet influences the excretion of urea. Safety precautions should be taken when handling any chemicals. HCl is corrosive, so care should be taken not to make contact with skin, and goggles should be worn. The same principles apply with the urine. ...read more.

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