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Planning exercise

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Planning exercise Aim: To plan an investigation to find out how changes in the consumption of protein in the diet influence the excretion of urea in humans. Introduction: I will need to measure the amount of urea produced by people with different protein intakes. I will use the enzyme urease to break the urea down into the alkaline ammonium carbonate and titrate this against an acid to find its concentration. Prediction: I think that the more protein the consumer has in their diet, the more urea will be secreted, therefore the ammonium carbonate will have a higher concentration. Hypothesis: Chains of amino acids make proteins. When too much protein is consumed those not needed for protein synthesis go through a process called deamination in the liver. The amino group and a hydrogen are removed from the amino acid and form ammonia (NH ) . This is then converted to urea which is less toxic and soluble. NO + CO = (NH ) CO. The urea is carried away by the blood to the kidney where it goes through the process of ultrafiltration before excretion. ...read more.


Allows you to have control over the volume which is added, the scale down the side shows the volume added in cc A pH metre Records the change in pH after the urease has been added. Shows big changes in pH clearly and accurately. syringe Extracts urine from sample collected. Shows volume of urine extracted in cc. The same volume must be used each time to make it a fair test. Conical Flask To mix the base and acid in. Narrow head allows acid to be added without causing any of the solution to splash out (thus changing the concentration). Test tube To mix the urea with water and urease in. Final method: -25cc of urine with 10% concentration of urea was used to create a calibration curve. This was used to compare the results against. -Nine subjects of the same age, weight, sex, and body build were divided into three groups. Each group was placed on a diet with a different protein intake for five days. One group had a restricted protein intake, one a healthy protein intake and the other an excess protein intake. ...read more.


CO : 1 (NH ) CO + 2HCL --> 2NH CL + H CO The moles of ammonium carbonate is equal to the number of moles of urea. -Concentration of urea in urine sample was calculated with the following equation: Number of moles of urea in sample X 1000 Volume of urine. - Procedure was repeated eight times. The mean from each group was calculated from those numbers. Choice of methods: -A different pH indicator could be used for titration such as phenolphthalein however this has a pH range of 8.2-10 and so would not coincide with the vertical section which is low due to the weak alkaline. - When James B Sumner carried out a similar experiment he momentarily warmed the urease up to 50 degrees C to speed the reaction up. However to get it precisely right each time is unlikely which I felt would make it an unfair test. If the temperature was too high it could denature the enzymes. Risk assessment: Risk Precaution Action if needed Acid skin corrosion Wear gloves Wash infected area immediately. Chemicals in eyes Wear protective goggles Wash eye Chemicals spilled Carry carefully, always make sure held in safe and secure container. Clean up wearing gloves. ...read more.

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