Physio Ex Exercise 8 Activity 3 PDF

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Physio Ex Lab Notes for Exercise 8 Activity 3. Expand more on the written questions to get a higher mark. ...

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8/9/2020

PhysioEx Exercise 8 Activity 3

PhysioEx Lab Report Exercise 8: Chemical and Physical Processes of Digestion Activity 3: Assessing Pepsin Digestion of Protein Name: Date: 9 August 2020 Session ID: 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: the stomach. 2 The substrate for pepsin is You correctly answered: protein and peptides. 3 In this activity the substrate you will be using to detect protein digestion is You correctly answered: BAPNA. 4 Negative results with the negative controls You correctly answered: are expected and validate the experiment. 5 A spectrophometer measures You correctly answered: optical density.

Experiment Results Predict Question 1 Predict Question: At which pH do you think pepsin will have the highest activity? Your answer: pH 2.0. Stop & Think Questions 1 Which of the following tubes are negative control tubes? You correctly answered: tubes 3 (pepsin, deionized water, pH 2.0 buffer) and 4 (deionized water, BAPNA, pH 2.0 buffer). 2 An optical density greater than zero indicates that You correctly answered: BAPNA digestion has occurred and pepsin is active. https://media.pearsoncmg.com/bc/bc 0media ap/physioex/10/ex8/act3/

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8/9/2020

PhysioEx Exercise 8 Activity 3

Experiment Data Tube No.

Reagent 1

Reagent 2

Reagent 3

Boiled

Time (min)

Temp (°C)

Optical Density

1

Pepsin

BAPNA

pH 2.0 Buffer

+

60

37

0.00

2

Pepsin

BAPNA

pH 2.0 Buffer

-

60

37

0.40

3

Pepsin

Deionized Water

pH 2.0 Buffer

-

60

37

0.00

4

Deionized Water

BAPNA

pH 2.0 Buffer

-

60

37

0.00

5

Pepsin

BAPNA

pH 7.0 Buffer

-

60

37

0.03

6

Pepsin

BAPNA

pH 9.0 Buffer

-

60

37

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: in the stomach. 2 Which two tubes validated the results of the experiment? You correctly answered: tubes 3 (pepsin, deionized water, pH 2.0 buffer) and 4 (deionized water, BAPNA, pH 2.0 buffer). 3 With more enzyme activity the optical density You correctly answered: increased. 4 If pepsin were digesting an actual protein substrate, the product would be You correctly answered: peptides and amino acids.

Review Sheet Results 1 Describe the effect that boiling had on pepsin and how you could tell that it had that effect. Your answer: Boiling the pepsin denatured the enzyme, causing it to have no effect on BAPNA. This is shown by how there were no activity shown in Test Tube #1. The protein was not ingested in Tube #1. There was no colour change and the optical density was at 0. The reason as to why boiling denatures enzymes is that at boiling temperatures, the chemical bonds that hold together the structure of enzymes begin to break down. This makes the enzyme to lose its structure and shape so that it will no longer fit their target substrate molecules. As a result, the enzymes stops functioning.

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PhysioEx Exercise 8 Activity 3

2 Was your prediction correct about the optimal pH for pepsin activity? Discuss the physiological correlation behind your results. Your answer: My prediction was correct that the optimal pH for pepsin activity was a pH of 2.0, the same pH level of gastric juice. The reason as to why pepsin functions the most at pH 2.0 is due to the carboxylic acid group on the amino acid in the enzyme's active site. The carboxylic acid group in the enzyme's active site must be bound to a hydrogen atom so that at low pH, it could catalyze the chemical reaction of breaking chemical bonds. At pH levels higher than 2, the carboxylic acid then becomes deprotonated and unable to participate in chemical reactions. Pepsin is the most active at a pH of 2.0 since its activity decreases at higher pH and drops off completely when it is over at pH 6.5. Enzyme activity is very sensitive to pH levels because the catalytic group, the carboxylic acid group, can be protonated or deprotonated, and these states usually determines if it could participate in a chemical reaction or not. 3 What do you think would happen if you reduce the incubation time to 30 minutes for tube 5 (pepsin, BAPNA, pH 7.0 buffer)? Your answer: If the incubation time were reduced to 30 minutes instead for tube 5, there might be no sign of digestion seen. At a full 60 minutes, there was only an optical density of 0.03. Therefore with only an incubation of 30 minutes, it is possible that no digestion would be seen at all as it could have an optical density of 0.01 or even lower.

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