Cellular Respiration and Carbon Dioxide
Purpose: To determine how exercise affects the disposal of wastes from cellular respiration.
Background:
Running requires a great deal of muscular activity. Muscles can only work when they contract.
Contracting muscles require a great deal of energy. This energy is obtained through the
process of cellular respiration. During this process, carbon dioxide is released by the muscle
cells as a waste product. If muscle activity is high, like it is when running on a steep slope, more
carbon dioxide will be produced. The excess carbon dioxide must be eliminated quickly
because it is toxic to the human body.
In this activity you will be using an indicator called bromothymol blue to check for the presence
of carbon dioxide. In a neutral solution, such as water, bromothymol blue is blue in color. In the
presence of an acid, bromothymol blue turns from green to yellow depending on the pH of the
solution. When carbon dioxide is added to water it forms a weak acid called carbonic acid.
Materials: (add this to your lab report)
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1 Erlenmeyer flask per partner group
1graduated cylinder per table
Medicine droppers or pipettes
1 plastic straw per group
Bromothymol blue solution
Clock or watch with second hand
Procedure:
1.
Add 20 mL of water to the flask. Add 4-5 drops of bromothymol blue to the water. Swirl the
flask to completely mix the color.
2.
Place a straw in the Erlenmeyer flask then place the flask on a sheet of white paper.
Your partner will time you during this step. When your partner says “go” breathing normal,
inhale through your nose and exhale through your mouth into the straws in solution. The
exhaled air should bubble gently in the solution.
CAUTION: DO NOT INHALE THROUGH THE STRAW.
3.
4.
Continue breathing in this fashion. DO NOT force breathing and be sure that all exhaled air
goes through the straw into the solution.
5.
When the solution changes color, your partner will say “stop,” and then record how long the
color change took.
6.
Empty and rinse your flask.
7.
Repeat steps 1 and 2.
8.
Jog in place for 1 minute (partner should be timing you).
9.
Dispose of your straws in the trash and clean up.
In your lab notebook write and answer the following.
Experimental Design:
Purpose
Independent Variable:
Dependent Variable
Control
3 Constants:
Data - Create an appropriate data table and graph for your results.
Cellular Respiration Lab Analysis (Answer in your lab journal):
1. What gas(es) does bromothymol blue serve as an indicator for?
2. What gas do you exhale?
3. What gas do plants give off?
4. What color did the bromothymol blue solution turn after you exhaled into it? Why?
5. How long (in seconds) did it take for the first solution to change color? For the solution after you
jogged in place for a minute? Was there a difference? Why?
6. What do you think would happen to the color of the bromothymol blue if you added an aquatic
plant into one of the flasks now? Why?
7. What is the purpose of cellular respiration?
8. Which cell organelle does cellular respiration take place in (name it and illustrate it)
9. Would you expect to find more or less of the organelle mentioned in #8 in the muscle cells of
athletes? Explain why.
10. What is ATP?
11. How does exercise affect the rate of cellular respiration?
12. In the space below, write out the balanced chemical equation for cellular respiration.
13.How are photosynthesis and Cellular Respiration similar? What are some differences?