PEX-08-02

Exercise 8: Chemical and Physical Processes of Digestion: Activity 2: Exploring Amylase Substrate Specificity Lab Report Pre-lab Quiz Results You scored 100% by answering 5 out of 5 questions correctly. 1. Which of the following is true of enzymes and substrates? substrates? You correctly answered: c. Enzymes are specific about the substrates they can act upon. 2. Which of the following is/are reducing reducing sugars? You correctly answered: e. both glucose and maltose 3. Cellulose and starch are both You correctly answered: e. polymers of glucose and polysaccharides. 4. Proteins and peptides are are formed by joining amino acids with a special type of covalent bond called a peptide bond. Which of the following enzymes do you think would be specific for a peptide bond? You correctly answered: c. peptidase 5. The Benedict's assay tests tests for for the presence of You correctly answered: c. reducing sugar.

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Experiment Results Predict Question: Predict Question: Do you think test tube 3 will show a positive Benedict's test? Your answer : b. no Stop & Think Questions: You included tube 2 to You correctly answered: b. see what a positive Benedict's test should look like. Which tube is included to detect contaminating amylase in the buffer or in cellulose? You correctly answered: d. tube 4 What is the usual substrate for the pancreatic enzyme peptidase? You correctly answered: d. peptides Experiment Data: Tube No. 1 2 3 4 5 6

Reagent 1 Amylase Amylase Amylase Cellulose Peptidase Bacteria

Reagent 2 Starch Glucose Cellulose Water Starch Cellulose

Reagent 3 pH 7.0 pH 7.0 pH 7.0 pH 7.0 pH 7.0 pH 7.0

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Time 60 60 60 60 60 60

Temp. 37 37 37 37 37 37

IKI + + + -

Benedict's ++ ++ ++

Post-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1. The substrate(s) for amylase is/are You correctly answered: a. starch. 2. The results of tube 5 demonstrated demonstrated that that You correctly answered: b. peptidase does not digest starch. 3. Why was the cellulose in tube 6 hydrolyzed to glucose? You correctly answered: d. The bacterial suspension contained the enzyme cellulase, which digested the cellulose. 4. Can you detect detect the presence of contaminating amylase from your experiments? You correctly answered: c. It is not possible to determine whether contaminating amylase is present because amylase doesn't digest cellulose.

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Review Sheet Results 1. Describe why the the results in tube 1 and tube 2 are the same. Your answer: In tube #1 the amylase is hydrolyzing the starch to glucose and in tube #2 the glucose is already present in the hydrolyzed form. 2. Describe the result in tube 3. How well did the results compare with your prediction? Your answer: The correct prediction is “no”. Tube #3 should not be positive for the Benedict’s test because amylase should not digest cellulose. 3. Describe the usual substrate substrate for peptidase. Your answer: . The usual substrate for peptidase is peptides and proteins. 4. Explain how bacteria can aid in digestion. Your answer: Bacteria can aid in digestion by breaking down cellulose which we do not produce cellulase.

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