1. Describe why the results in tube 1 and tube 2 are the same.
2. Describe the result in tube 3. How well did the results compare with your prediction?
3. Describe the usual substrate for peptidase.
4. Explain how bacteria can aid in digestion.
1. No, amylase doesn’t use cellulose as a substrate. Starch is the substrate for amylase.
2. The bacteria were able to digest the cellulose because they produce the enzyme, cellulase.
3. The peptidase had no effect on the starch because the substrate for peptidase is peptides and proteins.
4. The smallest subunit that starch can be broken down into is glucose.
1. Describe the effect that boiling had on pepsin and how you could tell that it had that effect.
2. Was your prediction correct aboutthe optimal pH for pepsin activity? Discuss the physiological correlation behind your results.
3. What do you think would happen if you reduced the incubation time to 30 minutes for tube 5?
1. The optimum pH matches the pH secreted by gastric glands. Gastric juice is also about pH 2.
2. Since the pH of the mouth is closer to neutrality, you would expect pepsin to be slightly active but not as
active as it is in the stomach at pH 2.
3. The subunit products of digestion are peptides and amino acids.
4. The control tube #4 is present to make certain that the BAPNA is not breaking down due to the low pH.
1. Describe the activity of lipase with and without the addition of bile salts. Refer to Chart 4 for pH values.
2. Is the activity of bile a chemical or a physical process? Explain.
3. What pH resulted in the maximum pancreatic lipase activity? How does this optimal pH correlate to the enzyme's location in the body?
4. Explain whether or not we can determine fat hydrolysis in tube 5. Why or why not?
1. Lipase activity is measured by a decrease in pH through the release of fatty acids.
2. The pH in tube #5 is pH 2.0. The pH is too low to be able to see if any fatty acids have been released.
3. Pancreatic lipase would be active in the mouth since the pH of the mouth is close to 7.0 and the enzyme is
most active at this pH.
4. Fat globules are separated into droplets by bile salts through an emulsification process which is physical
not chemical.