The biuret method for total serum protein is used for serum but not for protein in urine or cerebrospinal fluid (CSF) because: The method is not sufficiently sensitive for use with urine or CSF. Ammonium ions in CSF interfere with the reaction. Protein is not the major solute present in urine. The color of CSF interferes with a reading at 550 nm.
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Step 1: State the biuret reaction principle — the biuret reagent (Cu2+ in alkaline solution) forms a purple complex with peptide bonds in proteins; the complex is measured spectrophotometrically (around 540–560 nm). Show more…
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DETERMINATION OF TOTAL PROTEINS IN SERUM USING THE BIURET REAGENT: INTRODUCTION Proteins have several functions to perform in the body. There are different fractions of proteins, many factors control or influence the levels of proteins in the body. PROCEDURE: 1. Take 2mls of the Biuret Reagent (light blue) into a clean test tube. 2. Add 40ul of serum to the reagent and mix gently 3. Leave on the Laboratory bench for 10minutes, the colour will change to violet blue or deep blue. 4. Take 40ul of the standard into another test tube containing 2mls of Biuret Reagent and leave on the bench for 10 minutes 5. You then read the optical densities of the test sample and standard sample at 540nm. 6. Calculation: OD OF TEST x CONC OF STD=xg/L OD OF STD Reference Range: 66-83g/L Questions: 1. Each bench should show their calculations using the above formula and make a one line comment of result. 2. Discuss 5 metabolic functions of proteins. 3. Mention 4 different plasma proteins. 4. State only 5 factors that can cause a decrease level in plasma proteins. 5. What is protein electrophoresis? (Not more than 5 lines). 6. State only 5 factors that can influence the movement of protein during electrophoresis. 7. Apart from electrophoresis, state only 2 other ways by which proteins can be separated. 8. By means of a neat table mention 5 common enzymes, their site of production and one major function of each.
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The Biuret test is used to test for the presence of an amino acid. True False Casein can be isolated from milk by bringing it to its isoelectric point. True False Biuret reagent is used to confirm the presence of protein. Which of the following do you expect to give a positive Biuret test? Deionized water Glutamic acid (an amino acid) Casein More than one of these will give a positive Biuret test. Albumin is a protein. Do you expect a solution of albumin to be able to neutralize a small amount of acid? Yes, because albumin can function as a base. Yes, because albumin can function as an acid. No, because albumin cannot function as a base. No, because albumin cannot function as an acid. Albumin is a protein. Do you expect a solution of albumin to be able to neutralize a very large amount of acid? Yes. No.
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Carbohydrates Sample Test Tube # Biuret's Result (protein) Color +/- Distilled Water 1 Albumin (protein) 2 Chicken Broth 3 Table 3.2 - Please indicate the color of your result & whether it was + or - for the Biuret test. What type of bond does the Biuret reagent react with? _________________________________ As indicated in the table above, albumin is a protein. Why bother to test this sample for the presence of proteins? Which sample(s) contained the most protein according to your results? _____________________ Explain why you think this is the case:
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