physioex post lab questions

Name: john
Exercise 8: Chemical and Physical Processes of Digestion: Activity 3: Assessing Pepsin Digestion of Protein Lab Report
Pre-lab Quiz Results
You scored 40% by answering 2 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
Your answer : a. pepsin.
Correct answer: d. BAPNA.
4. Negative results with the negative controls
Your answer : a. are expected.
Correct answer: d. are expected and validate the experiment.
5. A spectrophometer measures
Your answer : b. starch concentration.
Correct answer: 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?
You did not answer this question.
Stop & Think Questions:
Which of the following tubes are negative control tubes?
Your answer : d. tubes 2 and 4
Correct answer: e. tubes 3 and 4
An optical density greater than zero indicates that
Your answer : a. BAPNA digestion has occurred.
Correct answer: 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 75% by answering 3 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?
Your answer: d. tubes 4 and 5
Correct answer: 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.
You did not answer this question.
2. Was your prediction correct about the optimal pH for pepsin activity? Discuss the physiological correlation behind your results. You did not answer this question.
3. What do you think would happen if you reduce the incubation time to 30 minutes for tube 5?
You did not answer this question.

09/22/13

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