Exercise 8 Chemical and Physical Processes of Digestion, pg. 105
Introduction: In this lab, I will learn how the complex digestive system breaks down substrates such as fats, proteins and carbohydrates.
Activity 1: Assessing Starch Digestion by Salivary Amylase
Data:
Chart 1 – Salivary Amylase Digestion of Starch
Tube # 1 2 3 4
Additives Amylase, Starch Amylase, Starch Amylase, DI Water DI Water, Starch
pH 7.0 buffer pH 7.0 buffer pH 7.0 buffer pH 7.0 buffer
Incubation Cond. Boil, Inc. 37 deg.C 37 degrees C 37 degrees C 37 degrees C
for 60 minutes
IKI Test: + - - +
Benedict's Test: - ++ - -
Chart1 – Salivary Amylase Digestion of Starch (5,6, 7)
Tube # 5 6 7
Additives DI Water, Maltose Amylase, Starch Amylase, Starch
pH 7.0 buffer pH 2.0 buffer pH 9.0 buffer
Incubation Cond. 37 degrees C 37 degrees C 37 degrees C
IKI Test: - + +
Benedict's Test: ++ + +
Questions: Please answer the questions in complete sentences and explain you answers.
1. What ph allowed the highest amylase activity and why? Please explain. pH buffer 7.0 allowed the highest amylase activity because, if the pH was lower than that or higher than 7.0, enzymes are still present in the amylases.
2. What effect does boiling have on enzyme activity? Boiling inactivates, or denatures enzymes.
3. Would the amylase present in the mouth be active in the stomach? Please explain your answer. Yes, because chemical digestion began in the mouth and ends in the stomach.
4. Does amylase digest peptidase? No, amylase digests starch and sugar.
5. Which tubes indicate that deionized water did not contain contaminating starch or maltose? Tube 3 did not contain contaminating starch or sugar.
Summary:
In this Activity, I learned/observed that: pH buffers higher or lower than 7.0 effects enzyme activity, which is activated by heat. I also observed the effects that boiling has on enzyme activity.
Activity 2: Assessing Cellulose Digestion
Data:
Chart 2 - Enzyme Digestion of Starch and Cellulose
Tube # 1 2 3 4
Additives Amylase, Starch Amylase, Starch Amylase, Glucose Amylase, Cellulose
pH 7.0 buffer pH 7.0 buffer pH 7.0 buffer pH 7.0 buffer
Incubation Cond. Freeze, Inc. 37 degrees C 37 degrees C 37 degrees C
37 deg C for 60 min 60 min. 60 min. 60 min.
IKI Test - - - +
Benedict's Test ++ ++ ++ -
Chart 2 Enzyme Digestion of Starch and Cellulose (Tubes 5, 6, 7)
Tube # 5 6 7
Additives Amylase, Cellulose Peptidase, Starch Bacteria, Cellulose
DI Water pH 7.0 buffer pH 7.0 buffer
Incubation Cond. 37 degrees C 37 degrees C 37 degrees C
60 min. 60 min. 60 min.
IKI Test + + -
Benedict's Test - - ++
Questions: Please answer the questions in complete sentences and explain your answers.
1. Which tubes showed that starch or cellulose was still present? Tubes 4, 5, and 6 stilled showed that starch was still present.
2. Which tubes tested positive for the presence of reducing sugars? No tubes tested positive for reducing sugar.
3. What was the effect of freezing tube 1? Freezing the tube didn’t cause any effects. I got the same results for tube 1 and 2, and both tubes contained the same reagents.
4. Does amylase use cellulose as a substrate? (Hint: Look at the results for Tube 4). No, amylase uses starch as a substrate.
5. What effect did the addition of bacteria have on the digestion of cellulose? The effect that bacteria had on the digestion of cellulose is, when it was amylases, the tube tested positive for cellulose and digested the sugar. But when the bacteria were added, the cellulose was digested in the tube, but there was an addition to the sugar in the tube.
Summary:
In this Activity, I learned/observed that: Bacteria uses cellulose as a substrate to digest in the body. Amylases caused no effect on the digestion of cellulose.
Activity 3: Assessing Protein Digestion by Pepsin
Data:
Chart 3 - Pepsin Digestion of Protein
Tube # 1 2 3 4
Additives Pepsin, BAPNA Pepsin, BAPNA Pepsin, DI Water DI Water, BAPNA
pH 2.0 buffer pH 2.0 buffer pH 2.0 buffer pH 2.0 buffer
Incubation Cond. Boil, Inc. 37 deg.C 37 degrees C 37 degrees C 37 degrees C
for 60 minutes 60 min. 60 min. 60 min.
Optical Density 0.00 0.40 0.00 0.00
Chart 3 - Pepsin Digestion of Protein (continued)
Tube # 5 6
Additives DI Water, BAPNA Pepsin, BAPNA
pH 7.0 buffer pH 9.0 buffer
Incubation Cond. 37 degrees C 37 degrees C
60 min. 60 min.
Optical Density 0.03 0.00
Questions: Please answer the questions in complete sentences and explain your answers.
1. Would pepsin be active in your mouth? No, because pepsin in the mouth is around 6.0.
2. What location in the body does Pepsin have the greatest activity? Pepsin has the greatest activity in the stomach.
3. What are the substrates and the subunits in this experiment? In this experiment, BAPNA is the substrate and amino acids are the subunits.
4. What would happen if you decreased the incubation temperature to 0 degrees? I think that there would be less digestion, due to the fact that enzyme activity is at its greatest at body temperature (37* C).
5. What effect did boiling have on Pepsin activity? Boiling the tube made the pepsin activity denature.
Summary:
In this Activity, I learned/observed that: Pepsin digested protein in the stomach, but because of its low pH, it will not digest protein in the mouth. I also observe how heat inactivated pepsin activity.
Activity 4: Assessing Fat Digestion by Pancreatic Lipase and the Action of Bile
Data:
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Chart 3 - Pancreatic Lipase Digestion of Fats and the Action of Bile
Tube # 1 2 3 4
Additives Lipase, Veg. Oil, Lipase, Veg. Oil, Lipase, DI Water, DI Water, Veg. Oil,
Bile salts DI Water Bile salts Bile salts
pH 7.0 buffer pH 7.0 buffer pH 9.0 buffer pH 7.0 buffer
Incubation Cond. 37 degrees C 37 degrees C 37 degrees C 37 degrees C
60 min. 60 min. 60 min. 60 min.
pH 6.21 6.72 9.00 7.00
Chart 3 - Pancreatic Lipase Digestion of Fats and the Action of Bile
Tube # 5 6
Additives Lipase, Veg. Oil, Lipase, Veg. Oil,
Bile salts Bile salts
pH 2.0 buffer pH 9.0 buffer
Incubation Cond. 37 degrees C 37 degrees C
60 min. 60 min.
pH 2.00 8.97
Questions: Please answer the questions in complete sentences and explain your answers.
1. At what ph did lipase have the greatest activity? Lipase had the greatest activity at pH 9.0.
2. Is the activity of bile a chemical or physical process? Please explain your answer. The activity of bile is a physical process I believe, because bile breaks up fats so that they are more accessible to digestive enzymes.
3. What is the substrate in the experiment? What are the subunits? Vegetable oil is the substrate and fatty acids are the subunits in this experiment.
4. In theory, would lipase be active in the stomach or your mouth? Please explain your answer. No, it would not be active in the mouth, because lipase works better at a pH of 4.5 – 5.4. But it would be active in the stomach.
5. Can we determine if fat hydrolysis has occurred in test tube 5? Please explain your answer. Yes, I can determine if fat hydrolysis in tube 5 and my conclusion is fat hydrolysis has not occurred because of the low pH indicating that there are still fatty acids present.
6. What happens to lipase activity if it is boiled? After doing the experiment over and boiling the tubes, I found that boiling increases lipase activity. All of the tubes pH measurements increased, except tube 5, which the pH remained the same as the last run.
Summary:
In this Activity, I learned/observed that:
Activity 5: Studying Mechanisms of Food Propulsion and Mixing: Deglutition (Swallowing)
Data: No data needs to be submitted.
1. While swallowing a mouthful of water from a paper cup, consciously note the movement of your tongue during the process. Record your observations. The back of the tongue pushes against the back of the throat closing off the area so that the water is pushed down.
2. Repeat the swallowing process while your laboratory partner watches the externally visible movements of your larynx. This movement is more obvious in a male, who has a larger Adam's apple. Record your observations. The larynx moves up, which helps with swallowing.
3. What do these movements accomplish? It’s preventing the water from entering the airway.
4. Interval between arrival of water at the sphincter and the opening of the sphincter: _______8_____ seconds
5. Explain the significance of the movement of the tongue during swallowing. The tongue initiates and controls the buccal phase of swallowing by pushing food into the pharynx.
6. Describe three events that occur during the pharyngeal-esophageal phase of deglutition. The three events that occur during the pharyngeal esophageal phase of deglutition is (1). The uvula and larynx rise to prevent food from entering respiratory passageways. The tongue blocks off the mouth. The upper esophageal sphincter relaxes, allowing food to enter the esophagus. (2). Small muscles that elevate the soft palate close off the nasal passages to prevent food from entering the esophagus inferiorly. (3). Food is propelled through the pharynx into the esophagus to the stomach by peristalsis.
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