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Scholar Name: Class: College Prep Biology Period: Teacher: Mr. Free Date: 09/17/2014 W Waarrm mU Upp:: ““TTeessttiinngg ffooooddss ffoorr P Prrootteeiinn”” Lesson Objectives Objective 1: Scholars understand that proteins are macromolecules with amino acid monomers. Objective 2:Scholars will then use Biuret’s reagent to test for the presence of protein ( Biuret Test). DIRECTIONS: Read the following information and complete the Warm Up Task. Background Information: Just like glucose and starch, protein is also a chemical that our food may be made from. Protein is similar to starch in that it is made from chains of smaller molecules. However, protein is not a carbohydrate, so the smaller molecules are not glucose, but other chemicals called amino acids. Warm Up Task: Now that scholars have mastered the scientific method, below are 4 steps in random order on how one could test for the presence of proteins using Biuret’s test. Using your knowledge of experimental procedures, what do you think should be correct order for this experimental procedure? (A) If testing more than one liquid, label each test tube with a marker. (B) To a test tube, add up to a third of the test tube, the liquid to be tested. (C) Note any color change. Proteins will turn solution pink or purple. (D) Add Biuret reagent (3 drops of copper sulfate and 10 drops of sodium hydroxide solutions) to each test tube. Shake gently to mix. WARM UP RESPONSE: The correct order of the steps should be ___, then,___, next___ and finally ___. Class Notes as Mr. Free teaches the scholars: Move the following labels to the correct test tubes in the picture Blue Colour Protein present NO Protein present Conclusion: Biuret Reagent changes from …………. to ……………… color when protein is present. Discussion: Biuret reagent is a mixture of sodium …………….. and copper ………….. . It is the copper sulfate that gives the Biuret reagent its blue color. Purple Colour Scholar Name: Class: College Prep Biology Period: Teacher: Mr. Free Date: 09/17/2014 Proteins are essential to us because we use them for gr……… of new bones skin etc. and the re…….. of damaged tissue. Your body also uses proteins to control the chemical reactions in our body and can also be used as an energy source. Some common examples of protein foods include mi…, f……, m….. eggs and seeds. Discuss any problems or ways to improve the experiment. Scholar Name: Class: College Prep Biology Period: Teacher: Mr. Free Date: 09/17/2014 MACROMOLECULE LAB REPORT: Testing food samples for protein (a) In your lab write up, record your observations in the table below and analyse your findings using the new knowledge you learned in Mr. Free’s class today. (b) Label six test-tubes 1-6. (c) If the food is a solid, crush a small piece (about 5 mm cube) in a mortar with about 10 cm3 water. (If the food is a liquid, simply pour about 20 ml of it into a test-tube.) (d) Pour about 20 ml of the crushed mixture or liquid into a test-tube. (e) Add about 10 ml of Biuret’s reagent or indicator (Indicator contains sodium hydroxide and copper sulphate (HANDLE WITH CARE *) (f) Shake the tube gently sideways to mix the contents. Return the tube to the rack and wait for a few seconds. (g) Record the results in the table in your lab report. Food Result on adding sodium hydroxide and copper sulphate Interpretation Milk Egg white Egg Yolk Agar Gel Water Glucose Solution * CARE. Sodium hydroxide is caustic and dissolves clothing, skin and bench tops. It is destructive, so if any is spilt on the bench, neutralize it at once with an equal volume of dilute hydrochloric acid and wipe dry. If spilt on clothing, do the same but follow with a wash in as much water as possible. If spilt on the skin, do not add acid but wash under the tap until the 'soapy' feeling is removed. Data Analysis and Discussion 1 In which of your samples do you think protein is fairly abundant? 2 In which samples do you think protein is absent or in very low concentration? 3 If one of your samples gives no purple colour with the biuret test, does this result mean the sample contains no protein? Scholar Name: Class: College Prep Biology Period: Teacher: Mr. Free Date: 09/17/2014 4 If a food sample gives a purple colour with the biuret test does this mean that it contains only protein?