Name: Group 7a Exercise 8: Chemical and Physical Processes of Digestion: Activity 3: Assessing Pepsin Digestion of Prote
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Name: Group 7a Exercise 8: Chemical and Physical Processes of Digestion: Activity 3: Assessing Pepsin Digestion of Protein Lab Report 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: b. the stomach 2. The substrate for pepsin is You correctly answered: d. protein and peptides. 3. In this activity the substrate you will be using to detect protein digestion is You correctly answered: d. BAPNA. 4. Negative results with the negative controls You correctly answered: d. are expected and validate the experiment. 5. A spectrophometer measures You correctly answered: c. optical density.
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Experiment Results Predict Question: Predict Question: At which pH do you think pepsin will have the highest activity? Your answer : c. pH 9.0 Stop & Think Questions: Which of the following tubes are negative control tubes? You correctly answered: e. tubes 3 and 4 An optical density greater than zero indicates that You correctly answered: e. BAPNA digestion has occurred and pepsin is active. Experiment Data: Tube No.
Reagent 1
Reagent 2
Reagent 3
Boiled
Time
Temp.
1 2 3 4 5 6
Pepsin Pepsin Pepsin DeIonized Water Pepsin Pepsin
BAPNA BAPNA DeIonized Water BAPNA BAPNA BAPNA
pH 2.0 Buffer pH 2.0 Buffer pH 2.0 Buffer pH 2.0 Buffer pH 7.0 Buffer pH 9.0 Buffer
+ -
60 60 60 60 60 60
37 37 37 37 37 37
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Optical Density 0.00 0.40 0.00 0.00 0.03 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: b. in the stomach. 2. Which two tubes validated the results of the experiment? You correctly answered: c. tubes 3 and 4 3. With more enzyme activity the optical density You correctly answered: a. increased. 4. If pepsin were digesting an actual protein substrate, the product would be You correctly answered: c. peptides and amino acids.
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Review Sheet Results 1. Describe the effect that boiling had on pepsin and how you could tell that it had that effect. Your answer: Pepsin activity break up ingested proteins and polypeptides into smaller peptide chains and free amino acids, therefore the zero optical density. 2. Was your prediction correct about the optimal pH for pepsin activity? Discuss the physiological correlation behind your results. Your answer: pH has an influence on the activity of the enzyme pepsin. It correlates with our prediction. 3. What do you think would happen if you reduce the incubation time to 30 minutes for tube 5? Your answer: It does not absorb the light and will have an optical density near zero.
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