BI101 Unit 2 Experiment

 

Read through the introductory materials below.

Open the Unit 2 Experiment Answer Sheet and complete the following Experiment exercises this unit:

Experiment 2 Exercise 1A – Effect of substrate concentration on enzyme function (~30 min)
Experiment 2 Exercise 1B – Effect of pH on enzyme function (~30 min)
Experiment 2 Exercise 2 – Cellular Respiration and Photosynthesis (~1.5 hrs)

Save your completed Unit 2 Experiment Answer Sheet and submit it by Midnight Sunday (CT).

Enzymes – Introduction

This unit we will examine enzyme function using a virtual simulation. Be sure to review our online lecture on Energetics and pp 80 – 82 in your book. As we have learned this unit, enzymes are biological catalysts that can lower the activation energy required to allow reactions to proceed. Enzymes are very sensitive to the environment in which they work, meaning changes in substrate concentration, temperature, pH, salts and other chemicals can drastically alter their function. This is one of the reasons the buffers we learned about last unit are so important!

When you are ready to begin these two exercises, go to:

Bioman. No date. Enzymatic (Links to an external site.)

Procedure

1. Click on “Start a New Game” and follow the on-screen instructions.
2. When you get to the “Main Menu”, click on “Experiments”.  You will have to click twice.
3. Click “OK” and follow the on-screen instructions.  Please note that you do not need to submit the answers from the quiz.

You will need an understanding of the different types of experimental variables in order to correctly graph your results. There are three different types of variables:

Independent Variable: This is the variable that the experimenter manipulates and is expected to affect the dependent variable. For example, if you think the amount of sunlight affects plant growth, you would vary the amount of light a plant receives (e.g., 2 hrs/day, 4hrs/day, 6 hrs/day). The amount of sunlight would be the independent variable.

Dependent Variable: This variable is expected to vary depending on the independent variable. In the example above, plant growth would be the dependent variable, because it is dependent on the amount of sunlight it receives.

Control Variable: This type of variable includes factors (there may be many) that could affect the outcome of your experiment. By holding these variables constant in all treatments, the experimenter knows that only the independent variable is affecting the outcome. In the example above, the variables you would want to hold constant would be things such as temperature, water and nutrients.

When graphing your results, the two variables of interest are the independent and dependent variables. The independent variable is always graphed on the x-axis and the dependent variable is always graphed on the y-axis. When you generate a graph, you must also always label each axis and include any units of measure.

When you are ready to begin, use the instructions in the Unit 2 Experiment Answer Sheet to complete these exercises.

Cellular Respiration and Photosynthesis – Introduction

In this exercise, you will have the opportunity to explore the relationship between the air we breathe and the plants around us. Be sure to review our online lecture on Energetics and Chapters 6 and 7 in your book; particularly pp 92-93.

Cellular respiration is the metabolic pathway in which all plants and animals extract usable energy (ATP) from foods either eaten (animals) or synthesized (plants). Yes, plants perform cellular respiration! This is because the energy they generate via photosynthesis is used to produce sugars. It is these sugars that are then broken down by cellular respiration to provide the energy to carry out plant cellular functions, just like in animal cells!

Cellular respiration and photosynthesis are linked by their reactants and products. Here is a chemical summary of the two reactions:

Cellular Respiration:     Oxygen + Glucose » Energy + Carbon dioxide + Water

Photosynthesis:             Energy + Water + Carbon dioxide » Glucose + Oxygen

What do you notice about the reactants and products of these two processes? RIGHT! The reactants of cellular respiration are the products of photosynthesis and the products of cellular respiration are the reactants of photosynthesis. Without photosynthesis and the production of oxygen, aerobic cellular respiration could not occur. And, carbon dioxide levels would increase significantly!

In this exercise, you will demonstrate this relationship between these two important processes using snails and Elodea, a water plant. When you are ready to start this exercise, go to:

Virtual Labs Simulation

http://www.classzone.com/cz/books/bio_09/resources/htmls/virtual_labs/virtualLabs.html (Links to an external site.)

If a link to Carbon Transfer through Snails and Elodea is not directly available, then follow these instructions:

• 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

You will need to open the Unit 2 Experiment Answer Sheet and follow the instructions carefully. The simulation is a little clunky to use and if you don’t do things right, you will have to start over. You must complete certain steps before you can proceed.

WEEK2 EXPERIMENT ANSWER SHEET

Please submit to the Week 2 Experiment “Submit Assignment” tab no later than Sunday midnight.

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 temperature on enzyme function, while holding enzyme concentration, pH and temperature constant. Open the following website to get started:

Bioman. No date. Enzymatic

https://biomanbio.com/HTML5GamesandLabs/LifeChemgames/enzymatichtml5page.html

Procedure

A. Click on “Start a New Game” and follow the on-screen instructions.

B. When you get to the “Main Menu”, click on “Experiments”. You will have to click twice.

C. Click “OK” and follow the on-screen instructions. Please note that you do not need to submit the answers from the quiz.

Questions

1. In this Experiment, which variable is the dependent variable and which is the independent variable (2 pts)?

2. Describe the relationship between temperature and enzyme activity (1 pts).

3. What is the temperature and enzyme activity was the highest (1 pts)?

4. What happens when the temperature becomes too high? Cited your sources. (2pts)

5. What happens when the temperature become too low? Cited your sources. (2pts)

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:

Procedure

A. Continue from the previous experiment by clicking “OK”. Follow the on-screen instructions.

Questions

1. In this Experiment, which variable is the dependent variable, and which is the independent variable (2 pts)?

2. Describe the relationship 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 (4 pts).

Experiment 2 Exercise 2: Cellular Respiration and Photosynthesis

In this exercise, you will test the following hypothesis by predicting results based upon the experimental set-up.

a. Hypothesis – Aquatic animals require the presence of plants to provide them with oxygen (via photosynthesis) needed for cellular respiration.

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.

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.

Indicator is added to detect the presence of carbon dioxide.

· Blue – no carbon dioxide

·

Green

– medium level of carbon dioxide

· Yellow – high level of carbon dioxide

Table 3. Predicted Results (

6 pts

).

Green

Green

Green

Green

Green

0 snails, 1 Elodea

Green

Green

Test Tube	Contents	Starting Color	Predicted End Color	Explain
1D	0 snails, 0 Elodea								Green
2D	1 snails, 0 Elodea
3D		0 snails, 1 Elodea
4D	1 snails, 1 Elodea ,
1L	0 snails, 0 Elodea,
2L	1 snails, 0 Elodea,
3L
4L	1 snails, 1 Elodea

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

8 pts

Experiment 2
Exercise 2

Component	Expectation	Points
Experiment 2 Exercise 1A	Demonstrates an understanding of the relationship between temperature and enzyme function and the ability to conduct an experiment and interpret results (Questions 1-5).		8 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).
	Experiment 2 Exercise 2	Follows instructions, correctly sets up experiment and records data (Tables 3).	6 pts
Demonstrates an understanding of the relationship between cellular respiration and photosynthesis and interpretation of experimental results (Questions 1-5)	11 pts
TOTAL	33 pts

Updated October 2013