Name: Hoang Le Minh 12MRLVTopic: Protein denaturationDate: 4th March 2014Time: 1 hour

Denaturing albuminI. Introduction

Research question

How does a change in heat, pH, the addition of 95% ethanol, and the addition of lead (II) nitrate/silver nitrate affect the solubility of albumin in eggs?

Hypothesis

I postulate that: In test tube 1 (investigating temperature), the albumin would undergo a colour change from clear to white and become water-insoluble. In test tube 2a (investigating acidic pH), the albumin would become water-insoluble. In test tube 2b (investigating alkaline pH), the albumin would become water-insoluble. In test tube 3 (investigating the effect of ethanol), the albumin would become water-insoluble In test tube 4 (investigating the effect of lead (II) nitrate), the albumin would become water-insoluble.

Variables

Controlled variables: Same starting concentration of albumin stock solution Test tube 1: Variables kept the same: pH, absence of ethanol, absence of lead (II) nitrate/silver nitrate Test tube 2: Variables kept the same: temperature, absence of ethanol, absence of lead (II) nitrate/silver nitrate Test tube 3: Variables kept the same: pH, temperature, absence of lead (II) nitrate/silver nitrate Test tube 4: Variables kept the same: pH, temperature, absence of ethanolDependent variable: Solubility of albumin Independent variable: Test tube 1: Temperature Test tube 2: pH Test tube 3: Presence of ethanol Test tube 4: Presence of lead (II) nitrate or silver nitrate

II. Procedures and materials

Apparatus 6 test tubes Test tube rack Pipettes Measuring cylinders BeakerSafety precautions Eye protectionProcedures

1. Prepare a stock albumen solution by adding the white of one egg to 100 ml of distilled water in a beaker. Stir until the albumin is in solution.2. Place 5 ml of albumen solution into each of six test tubes. Label the tubes Control, A, B1, B2, C, and D.3. Treat the four solutions as follows: Control: Let stand in room temperature. Measure the temperature and pH with pH paper. A: Heat in a hot water bath for a few minutes. B1: Add 2 ml of 1M HCl. Record the pH using pH paper. B2: Add 2ml of 10% NaOH. Record the pH using pH paper. C: Add 1 ml of 95% ethanol solution. D: Add 5 10 drops of 2% lead (II) nitrate.4. Record observations.III. Data collection and presentation

Results

Denaturing agentsObservation

Control test tube (pH 8, 240C)No change

A Heat, 650CTurns slightly cloudy.

B1 1M HCl, pH 1

B2 1M NaOH, pH 11Viscosity increases. Solution becomes thicker and runnier. However, no perceptible colour change is observed.

C 95% EthanolTurns cloudy, but not to the extent of test tube D. Turns cloudy at the top of the solution first, then eventually permeates to the entire body of the solution.

D Lead (II) nitrateCoagulates into a white solid immediately when coming into contact with lead (II) nitrate. Produces a white precipitate, soft when touched.

IV. Data processing

No quantitative data available.V. Conclusion and evaluation

1) What was the purpose of the controlled test tube?2) What common result occurred in all experimental tubes? Why?