Effect of pH on enzyme function

Effect of pH on enzyme function
SUMMARY OF ACTIVITIES FOR WEEK 2 EXPERIMENT ASSIGNMENT
· Experiment 2 Exercise 1a – Effect of substrate concentration on enzyme function
· Experiment 2 Exercise 1b – Effect of pH on enzyme function
· Experiment 2 Exercise 2 – Cellular Respiration and Photosynthesis
Experiment 2 Exercise 1A: Effect of substrate concentration on enzyme function
Review the Week 2 Experiment Introductions, our online lecture on Energetics and pp 80 – 82 in your book. For this exercise, we are going to look at the effect of substrate concentration on enzyme function, while holding enzyme concentration, pH and temperature constant. Open the following website to get started:
Procedure
A. Click on the TV/VCR and listen to the short overview about enzyme action. Close the window when done.
B. Then click on the Information button and review the information there. Close the window when done.
C. In our first experiment, we will determine the effect of different amounts of substrate on enzyme function. First, we need to set up the experiment:
a. Click on the 0.5 g substrate weigh paper and drag it to Tube #1; note the color change. When our enzyme breaks down the substrate, the solution turns blue. The intensity of the color indicates the amount of product formed.
b. Now drag the 1.0 g substrate weigh paper to Tube #2 and continue as such with the rest of the substrate samples as indicated in the table below.
c. Click on the computer monitor to view your results and transcribe them to Table 1 below.
Table 1. Substrate amount and product formation results (1 pts).

Test Tube Number
Amount of Substrate (g)
# of Molecules of Product Formed per Minute (X 106)

1
0.5
 

2
1.0
 

3
2.0
 

4
4.0
 

5
8.0
 

D. Generate a scatter plot of Amount of Substrate vs Molecules of Product Formed and paste it here. Be sure you label your axes and include units. If you need help generating a graph, see the tutorials mentioned in the Week2 Experiment Introduction (3 pts).
Questions
1. In this Experiment, which variable is the dependent variable and which is the independent variable (2 pts)?
2. Describe the relationship between substrate concentration and enzyme function (as estimated by product formation) as evidenced by your graph above (1 pts).
3. What is the maximum rate of product formation and at what substrate level did this occur (1 pts)?
Experiment 2 Exercise 1b: Effect of pH on enzyme function
Be sure to review the Week 2 Experiment Introduction, our online lecture on Energetics and pp 80 – 82 in your book. For this experiment, we are going to look at the effect of pH on enzyme function, while holding enzyme concentration, substrate concentration and temperature constant. Go to:
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Procedure
A. Click on Reset if necessary before beginning.
B. In our second experiment, we will determine the effect of pH on enzyme function. First, we need to set up the experiment:
a. First, you will need to adjust the pH in each test tube.
i. Use the up or down arrows beneath the test tubes.
ii. Set Tube #1 at pH 3 and Tube #2 to pH 5. Leave Tube #3 at pH 7. Set Tube #4 to pH 9 and Tube #5 to pH 11.
iii. Your test tube rack should now look like this:

C. Click on the paper containing 4.0 g of substrate and add it to each tube. Note that the amount of substrate is now a control variable and we add the same amount of substrate to each tube.
D. Click on the computer to view your results and transcribe your data to Table 2 below.
Table 2. pH and product formation amounts (1 pts).

Test Tube Number
pH
# of Molecules of Product Formed per Minute (X 106)

1
3
 

2
5
 

3
7
 

4
9
 

5
11
 

E. Generate a scatter plot in of pH vs Molecules of Product Formed and paste it here. Be sure you label your axes and include units (3 pts).
Questions
1. In this Experiment, which variable is the dependent variable and which is the independent variable (1 pts)?
2. Describe the relationship shown in your graph between pH and enzyme activity. At what pH did you see optimum enzyme activity (2 pts)?
3. Explain your results based on what you have learned about enzymes this week and the factors that affect their function. Cite your source (1 pts).
Experiment 2 Exercise 2: Cellular Respiration and Photosynthesis
To get started, go to:
Virtual Labs Simulation http://www.classzone.com/cz/books/bio_10/resources/htmls/virtual_labs/virtualLabs.html
· Select Missouri as your location and click Go
· Click on the Go beneath Biology 2010
· Under the Labs heading, click on Virtual Labs
· Click on Carbon Transfer through Snails and Elodea
Follow the instructions carefully. In many cases, you cannot proceed until you completed every step.
Procedure
A. Listen to the Problem and close the window when done.
B. Click on the Background tab and listen to the information presented. Close the window when done.
C. Explore the lab. Before you can set up the Experiments, you must click on the various items in the laboratory (sorry). See the list of items under Checklist on the right side of the page. Once you have click on each item you can move on.
D. Click on the Procedure tab to continue and then click on the Lab Notebook. You must enter information in the Lab Notebook in order to proceed. You will be given some of the information to enter and other information you will have to provide.
a. Hypothesis – Aquatic animals require the presence of plants to provide them with oxygen (via photosynthesis) needed for cellular respiration. <–READ first and then copy and paste it into the Hypothesis box in the Notebook.
The relationship mentioned in the hypothesis is illustrated in the diagram below:

In our experiment, we are using an aquatic environment, but the concepts are the same. The snails and Elodea will produce carbon dioxide via cellular respiration. The Elodea will use this carbon dioxide in photosynthesis to produce sugars. The oxygen required for cellular respiration will be generated by the Elodea via photosynthesis.
E. Leave the Notebook open and click on the tab next to Procedure (Step 1 of 7) to advance to Step 2.
F. Fill in the text boxes in the Lab Notebook by copying and pasting the information in italics below. You will need to use the slider on the right side of the Notebook to scroll down the page:
a. In my experiment, I will measure the level of CO2 by: bromothyol blue. Recall that in the presence of carbon dioxide, it will turn yellow.
b. In my experiment, my independent variable will be: The presence or absence of snails, the presence or absence of Elodea, and the use of light and dark.
c. The set-up condition for my control condition is: A test tube containing BTB.
d. I will use 8 test tubes.
e. Determine the set-up for each tube (Note the letters D and L refer to Dark and Light treatments):
Tube 1D: BTB only Tube 2D: BTB + 1 snail Tube 3D: BTB + 1 Elodea Tube 4D: BTB + 1 snail + 1 Elodea Tube 1L: BTB only Tube 2L: BTB + 1 snail Tube 3L: BTB + 1 Elodea Tube 4L: BTB + 1 snail + 1 Elodea
NOTE: Tubes 1-4D and 1-4L consist of the same treatments, except that one set will be placed in the dark (D) and the other in the light (L).
G. Close the Lab Notebook and click on the tab next to Procedure (Step 2 of 7) and advance to Step 3 and follow the lab set-up outlined above.
a. Distribute eight test tubes into the rack. Click on the box of test tubes and drag each one to the test tube rack.
b. Pour BTB into all eight test tubes. Click on the beaker of BTB and drag over the test tubes.
H. Click on the tab next to Procedure (Step 3 of 7) to advance to Step 4 and set up the design indicated above.
a. Click on the beaker of snails and drag one each into the appropriate tubes (2D, 4D, 2L, and 4L).
b. Click on the beaker of Elodea and drag a sprig into the appropriate tubes (3D, 4D, 3L, and 4L). Your eight test tubes should look like those below. If not, clear tubes and try again.

One rack of tubes (1D-4D) will be placed in the dark box for 24 hrs, while the other rack (1L-4L) will be exposed to light.
Click on the Lab Notebook and enter your predictions for the color in the test tubes at the end of the experiment. See the diagram below to locate where the information needs to be entered. Do not enter any End Colors yet. Recall the end color choices are:
· Blue – no carbon dioxide
· Green – medium level of carbon dioxide
· Yellow – high level of carbon dioxide

Do not enter any End Colors yet.
I. You will need to enter these same predictions in Table 3 below and explain your predictions. Close the Lab Notebook when you are done.
Table 3. Predictions (4 pts).

Test Tube
Contents
Starting Color
Predicted End Color
Explain

1D
0 snails, 0 Elodea
Green
 
 

2D
1 snails, 0 Elodea
Green
 
 

3D
0 snails, 1 Elodea
Green
 
 

4D
1 snails, 1 Elodea,
Green
 
 

1L
0 snails, 0 Elodea,
Green
 
 

2L
1 snails, 0 Elodea,
Green
 
 

3L
0 snails, 1 Elodea
Green
 
 

4L
1 snails, 1 Elodea
Green
 
 

J. Click on the tab next to Procedure (Step 4 of 7) to advance to Step 5.
a. Add stoppers to all of the test tubes (click on the two Add Stoppers buttons).
b. Drag the test tube rack on the left to the black box cover.
c. Drag the test tube rack on the right to the grow light.
K. Click on Start (near the clock) and allow the time to elapse. Then click on the tab next to Procedure (Step 5 of 7) to advance to Step 6.
L. Enter your results in Table 4 below. Recall that the amount of CO2 present is indicated by the color.
NOTE that you do not need to open the Lab Notebook to enter your results. You need only enter your results below. You are done with the simulation once you record your results.
Table 4. Results (2 pts).

Test Tube
Contents
Start Color
End Color
How much CO2 is present
(None, Medium, High)

1D
0 snails, 0 Elodea
Green
 
 

2D
1 snails, 0 Elodea
Green
 
 

3D
0 snails, 1 Elodea
Green
 
 

4D
1 snails, 1 Elodea
Green
 
 

1L
0 snails, 0 Elodea
Green
 
 

2L
1 snails, 0 Elodea
Green
 
 

3L
0 snails, 1 Elodea
Green
 
 

4L
1 snails, 1 Elodea
Green
 
 

Questions
1. In which treatment(s) did you see the greatest amount of carbon dioxide present? Explain why this was true for each treatment that had the greatest amount; be specific (3 pts).
2. In which treatment(s) did you see the least amount of carbon dioxide present? Explain why this was true for each treatment that had the least and explain what happened to the carbon dioxide that had been present (2 pts).
3. Was there any difference in your results between tubes 3D and 3L? If so, describe what the difference was and why (2 pts).
4. Based on your results, how do you know that snails produce carbon dioxide (2 pts)?
5. What was the purpose of tubes 1D and 1L (2 pts)?
 
Week 2 Experiment Grading Rubric

Component
Expectation
Points

Experiment 2 Exercise 1A
Follows instructions, correctly records data (Table 1) and generates a graph.
4 pts

Experiment 2 Exercise 1A
Demonstrates an understanding of the relationship between substrate concentration and enzyme function and the ability to conduct an experiment and graph and interpret results (Questions 1-3).
4 pts

Experiment 2 Exercise 1B
Follows instructions, correctly records data (Table 2) and generates a graph.
4 pts

Experiment 2 Exercise 1B
Demonstrates an understanding of the relationship between pH and enzyme function and the ability to conduct an experiment and graph and interpret results (Questions 1-3).
4 pts

Experiment 2 Exercise 2
Follows instructions, correctly sets up experiment and records data (Tables 3 and 4).
6 pts

Experiment 2 Exercise 2
Demonstrates an understanding of the relationship between cellular respiration and photosynthesis and interpretation of experimental results (Questions 1-5)
11 pts

TOTAL
 
33 pts

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