Procedure 2 test protein digestion

Procedure 2 Test Protein Digestion Next you will examine protein digestion with the enzyme pepsin. Recall that pepsin is produced by the chief cells as the inactive enzyme pepsinugen, and that pepsinogen requires certain conditions to become active. You will assess for protein digestion with the chemical Biuret reagent, which turns blue in the presence of undigested proteins and lavender-purple in the presence of amino acids (Fig. 24.26). 1 Obtain four test tubes and number them I through 4 with a Sharpie. Safety Note 2 Add about 3 ml of egg white (or albumin) to each test tube. Safety glasses and gloves are required! 3 Add 3 mL of pepsinogen in 0.1 M NaOH (PH about 8) to tube 1. 4 Add 3 ml of pepsinogen in 0.5 M hydrochloric acid (PH about 2-3) to tube 2. Negative Positive Reagent Reaction Reaction 5 Add 3 ml of 0.1 M NaOH to tube 3. 6 Add 3 ml of 0.5 M hydrochloric acid to tube 4. 7 Place each tube in a 37C water bath for one hour. Biuret reagent 8 Remove the tubes and add 5 drops of Biuret reagent to each tube. Record the color change that you observe in each tube in Table 24.4. FIGURE 24.26 Possible results with Biuret's test: light blue indicates no protein digestion, while light purple indicates amino acids are present. TABLE 24.4 Results of Protein Digestion Experiment Tube Color of Mixture after Adding Biuret Reagent Tube 1 (egg white + pepsinogen + NaOH) Tube 2 (egg white + pepsinogen + HCI) Tube 3 (egg white + NaOH) 24 Tube 4 (egg white + HCI) = Exploring Anatomy & Physiology in the Laboratory