7/10/2020 PhysioEx Exercise 8 Activity 3 PhysioEx Lab Report Exercise 8: Chemical and Physical Processes of Digestion Activity 3: Assessing Pepsin Digestion of Protein Name: Date: 10 July 2020 Session ID: session-0bc05dc9-6ﬀe-8acf-05c6-c85fa8002b99 Pre-lab Quiz Results You scored 100% by answering 5 out of 5 questions correctly. 1 Where in the body does protein digestion begin? You correctly answered: the stomach. 2 The substrate for pepsin is You correctly answered: protein and peptides. 3 In this activity the substrate you will be using to detect protein digestion is You correctly answered: BAPNA. 4 Negative results with the negative controls You correctly answered: are expected and validate the experiment. 5 A spectrophometer measures You correctly answered: optical density. Experiment Results Predict Question 1 Predict Question: At which pH do you think pepsin will have the highest activity? Your answer: pH 2.0. Stop & Think Questions 1 Which of the following tubes are negative control tubes? You correctly answered: tubes 3 (pepsin, deionized water, pH 2.0 buﬀer) and 4 (deionized water, BAPNA, pH 2.0 buﬀer). 2 An optical density greater than zero indicates that 1/3 7/10/2020 PhysioEx Exercise 8 Activity 3 You correctly answered: BAPNA digestion has occurred and pepsin is active. Experiment Data Tube No. Reagent 1 Reagent 2 Reagent 3 Boiled Time (min) Temp (°C) Optical Density 1 Pepsin BAPNA pH 2.0 Buﬀer + 60 37 0.00 2 Pepsin BAPNA pH 2.0 Buﬀer - 60 37 0.40 3 Pepsin Deionized Water pH 2.0 Buﬀer - 60 37 0.00 4 Deionized Water BAPNA pH 2.0 Buﬀer - 60 37 0.00 5 Pepsin BAPNA pH 7.0 Buﬀer - 60 37 0.03 6 Pepsin BAPNA pH 9.0 Buﬀer - 60 37 0.00 Post-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1 Pepsin would be most active You correctly answered: in the stomach. 2 Which two tubes validated the results of the experiment? You correctly answered: tubes 3 (pepsin, deionized water, pH 2.0 buﬀer) and 4 (deionized water, BAPNA, pH 2.0 buﬀer). 3 With more enzyme activity the optical density You correctly answered: increased. 4 If pepsin were digesting an actual protein substrate, the product would be You correctly answered: peptides and amino acids. Review Sheet Results 1 Describe the eﬀect that boiling had on pepsin and how you could tell that it had that eﬀect. Your answer: Boiling inactivated the pepsin. There was no activity observed in Tube 1 but it was very active in Tube 2. 2/3 7/10/2020 PhysioEx Exercise 8 Activity 3 2 Was your prediction correct about the optimal pH for pepsin activity? Discuss the physiological correlation behind your results. Your answer: Pepsin is the most active. My prediction was a pH of 2.0 was correct. 3 What do you think would happen if you reduce the incubation time to 30 minutes for tube 5 (pepsin, BAPNA, pH 7.0 buﬀer)? Your answer: If the incubation time was reduced to 30 min for Tube 5, I think there would be no digestion of protein. 3/3