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Investigation to find out how changes in the consumption of protein in the diet influence the excretion of urea in humans

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Investigation to find out how changes in the consumption of protein in the diet influence the excretion of urea in humans Aim: to investigate how a change in the protein consumption by humans affects their excretion of urea. We will take into account the two protein classes; the 1st class being animal, and the 2nd class being plant (not all essential amino acids). Prediction The more protein consumed, the higher the intake of nitrogen, this Nitrogen is then lost from the body in the form of urea. Therefore an increase in protein the diet should lead to an increased concentration in the urea (after the intake becomes greater than the body requires). As the intake of protein increases the concentration of urea will also rise; and the more alkaline the pH of the urine. Justification of the prediction Increased consumption of dietary protein is linearly related to the production of urea and urea excretion is controlled by the kidney. Urea + water ammonium carbonate If excess protein is consumed, it cannot be stored in the body. The proteins are comprised of amino acids, which contain useful energy. To obtain this energy the liver removes the nitrogen from these amino acids, and this is excreted as urea. The process by which urea is formed is deamination. The amino-group is removed and combines with a hydrogen atom, this produces ammonia. ...read more.


solution of urease -0.1mol dm-� Hydrochloric acid -Burette for measurements -Graduated pipettes -Conical Flasks -Burette for titrations -Stop clock -Thermostatically controlled water bath -pH buffer -White tile to help determine end point Revised method to find volume of Hydrochloric acid required * As in the preliminary experiments, test tubes of known urea concentrations are set up (as below): * Incubate each sample of urease, and the concentrations for 20 minutes at 37�C using the thermostatically controlled water bath. Test Tube Number Volume of Urea (cm�) Volume of Water (cm�) Concentration (%) Control 0 10 0 1 0.5 9.5 0.5 2 1 9 1 3 1.5 8.5 1.5 4 2 8 2 5 2.5 7.5 2.5 6 3 7 3 7 3.5 6.5 3.5 8 4 6 4 9 4.5 5.5 4.5 10 5 5 5 11 5.5 4.5 5.5 12 6 4 6 13 6.5 3.5 6.5 14 7 3 7 * Perform the following separately for each test tube: add 2cm� of urease using a graduated pipette. Immediately add 3 drops of Screened Methyl Orange. * Return the test tube to the thermostatically controlled water bath and further incubate for 15 minutes. * Remove the test tube, and pour the concentration into a conical flask. Use a burette of Hydrochloric Acid to titrate. Record the volume at the end point of the reaction, when the colour has changed from green to grey. ...read more.


Exercise All volunteers would take part in 30 minutes aerobic exercise a day, and follow a strict and identical plan. Exercise would result in muscle growth/regeneration which in turn requires protein. This would detract from the samples that would be taken, and the results gained would be marginally different from those who stuck to the exercise regime. Age and Sex Subjects chosen would all be male and between the ages of 25-30. Males are likely to have more muscle and so will utilise more protein. Subjects below the age of 21 are still developing, using protein for muscle growth. The narrow age range results in a similar use of protein. Diet Everyone must follow an identical diet, barring the controlled varied amount of protein. They must all drink the same volume of water. All sources must be controlled to ensure that only our dependant variable is shown to be effecting results. Water intake would affect dilution of urine - but if controlled would not be noticeably different between subjects. Temperature Each subject must be held in a similar environment, it must be monitored so that it stays relatively constant. This experiment is investigating a process involving enzymes, which are affected by temperature (see independent variable) Sources * Jones, M, Fosbery, R and Taylor, D. (2000) Biology 1, Cambridge: Advanced Sciences * Jones, M and Gregory, J. (2001) Biology 2, Cambridge: Advanced Sciences * http://www.nutritionandmetabolism.com/content/2/1/25 ?? ?? ?? ?? Amelia Wilson U6HW Centre Number: 28254 Candidate Number: 1121 06/05/2008 ...read more.

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