Lab 9 - Proteins and Carbohydrates

Lab 9 - Proteins and Carbohydrates - Jin Bae CHEM-242L...

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Jin Bae CHEM-242L Proteins and Carbohydrates: The Isolation of Casein and Lactose from Milk Performed: 4/05/2007 Written: 4/10/2007 Purpose The purpose of this lab is to isolate casein and Lactose from milk through a series of tests, which includes the Benedict’s test for reducing sugar. Reactions Tables of Reactants and Products Name Appearance Molar W M. point B. point Density Mercuric chloride 271.52 g/ mol 277 °C 302 °C 6.5 g/cm 3 Ethanol 46.08 g/mol −114.3 °C 78.4 °C 0.789 g/c Albumin 385 amino acids 45 kD Procedure A: 4.0g of powdered mild and 10ml of water was placed in 100ml beaker. The mixture was heated in a water bath to 40°C. 1.0ml of dilute acetic acid solution was added dropwise to the warm milk. Using the rubber policeman, the casein was pushed up onto the side of the beaker so that most of the liquid drains from the solid. Casein was removed. 0.2g of calcium carbonate was added to the milk. Liquid was taken out by Buchner funnel. B: Albumin: The mixture was heated to 75°C for about 5 minutes. The liquid was taken away. The albumin was pressed with a spatula to remove as much liquid as possible and the liquid was poured into the centrifuge tube. The liquid was cooled to the room temperature, centrifuged the contents of the tube for 3 minutes. Following centrifugation, the liquid was discarded from the solid into a beaker. Lactose: 15ml of 95% ethanol was added to the beaker containing the centrifuged and decanted liquid. The mixture was heated to about 60°C. The hot liquid was poured into a 40ml centrifuge tube and centrifuged for 3 minutes. Warm supernatant liquid was removed from the tube to a small Erlenmeyer flask. Lactose was collected by vacuum filtration. 3ml of 95% ethanol was added to aid transfer. C: Above 90°C hot water bath was prepared. 0.01g of lactose was dissolved in 1ml of water in a test tube. 1ml of each of 1% solutions of glucose and galactose was placed in separate test tubes. 2ml of Benedict’s reagents was added to each of the three test tubes. The test tubes were placed into the how water bath for 2 minutes. D: 1.0g of casein was placed in a test tube and 5.0ml of water and 2.0ml of 10% NaOH solution were added. A stopper was placed in the test tube, and was shaken. Concentrated
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Jin Bae CHEM-242L HCl was added dropwise with shaking. Adding HCl was continued until 4.0ml of acid had been added. The test tube was shaken. E: 2.0ml of egg albumin solution was placed in a test tube and boiled for a few minutes.
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Lab 9 - Proteins and Carbohydrates - Jin Bae CHEM-242L...

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