Name: __________________
Date: ___________
Period: ___________
Exercise and Cellular Respiration Lab
Introduction: What happens when you exercise? As you know, increasing your activity level
will cause an increase in your respiration rate. What you may not know is that this is closely
tied to cellular respiration in your cells. As you increase your activity, mitochondria in your
cells use oxygen to break down sugars to charge up ATP molecules; ATP is then used for
energy directly elsewhere in your cells, including muscle work. A waste product of the
breakdown of sugars is carbon dioxide gas, which you exhale.
For quick energy, the body uses already-stored ATP and new ATP made by lactic acid
fermentation. These sources can only supply enough ATP to last about 90 seconds! For
exercise longer than 90 seconds, cellular respiration is the only way to generate a continuing
supply of ATP. Cellular respiration releases energy more slowly than fermentation, which is
why you have to pace yourself during long sessions of exercise. Glucose is a common fuel for
the process of cellular respiration. The complex sugar, starch, is broken down into a simple
sugar, glucose, by the digestive system. Humans and many other animals store another form of
starch called glycogen in the liver and muscle cells. Glycogen can also be changed into glucose
and used to fuel cellular respiration. Glucose is not the only fuel the body can use. For
example, proteins and fats can also be used. Proteins are broken down into their monomer
amino acids and then modified to be used in the Kreb’s cycle with the help of enzymes. Fats,
whether taken in with food or stored in the body, provide excellent fuel for respiration. A
gram of fat produces more than double the amount of ATP than a gram of carbohydrate does.
Although in the lab we cannot physically see this breakdown, we will examine how exercise and
physical exertion affects cellular respiration.
If we were to increase our activity level, we should expect an increase in the amount of
carbon dioxide we exhale. This can be measured by a blue solution of BTB (bromothymol blue).
This chemical turns yellow-green in the presence of carbonic acid, the chemical resulting when
carbon dioxide gas mixes with water. All you need to do is blow through a straw into a solution
of BTB to detect it!
Prelab Questions:
1. Why does carbon dioxide increase during exercise?
____________________________________________________________
____________________________________________________________
2. How do we generate energy (ATP) for longer periods of exercise?
____________________________________________________________
____________________________________________________________
3. How are we observing the presence of carbon dioxide in this lab?
____________________________________________________________
____________________________________________________________
Purpose Question: How will exercise affect your cellular respiration rate?
Objectives by end of lab: I can…
• Describe the overall affect of exercise on cellular respiration.
• Describe the affect of exercise on carbon dioxide production.
• Describe how I illustrated the affects of exercise on CO2 production during this lab.
Procedure: We will be using bromothymol blue (BTB) solution as an indicator of CO2. As BTB
comes in contact with CO2, the blue solution will turn yellow-green. Do NOT ingest BTB!
1. Preparing the solution - Put 50 mL of water and a dropper full of BTB in each flask.
Cover the flask with parafilm. Then stick a straw through the parafilm.
2. While a partner times you, slowly blow air through a straw into the bottom of the flask
until the solution turns yellow/green (when carbon dioxide combines with the BTB it
changes the color from BLUE to YELLOW/GREEN). Do not let the solution get in your
mouth!
3. Record the time it takes for the color change to occur.
4. Dump out the BTB solution, rinse with tap water, and create another 50mL of BTB
solution.
5. Have the same person who blew through the straw in step 2 run up and down the stairs
for 1 minute.
6. After the time is up, have the runner blow through the straw again until the BTB
solution changes to the yellow-green color.
7. Record the time it takes for the color change to occur.
8. Dump out the BTB solution, rinse with tap water, and create another 50mL of BTB
solution.
9. Have the same runner run up and down the stairs for 1 minute 30 seconds.
10. After the time is up, have the runner blow through the straw again until
the BTB solution changes to the yellow-green color.
11. Record the time it takes for the color change to occur.
12. Dump out the BTB solution, rinse with tap water, and create
another 50mL of BTB solution.
13. Have the same runner run up and down the stairs for 2 minutes.
14. After the time is up, have the runner blow through the straw again until the
BTB solution changes to the yellow-green color.
15. Record the time it takes for the color change to occur.
16. Dump out the BTB solution, rinse with tap water, and create another 50mL of BTB
solution. Repeat the experiment with another group member.
Results:
Time Elapsed Before Color
Change – Person A
Before
exercise
After 1
minute
After 1.5
minutes
After 2
minutes
Time Elapsed Before Color
Change – Person B
Analysis:
Create a line graph of your data and your lab partner’s data. Answer the questions that follow.
Graph Key:
1. From your graph, which of your trials was longest to change the BTB? Why?
_____________________________________________________________________
_____________________________________________________________________
2. From your graph, which of your trials was shortest to change the BTB? Why?
_____________________________________________________________________
_____________________________________________________________________
3. From your graph, How does your data compare to your lab partners? (Was there a
difference?)
_____________________________________________________________________
_____________________________________________________________________
4. Which group member had the most efficient cellular respiration? Explain your answer.
_____________________________________________________________________
_____________________________________________________________________
5. What process in your body produces carbon dioxide? How did exercise affect this process?
_____________________________________________________________________
_____________________________________________________________________
6. What gas was present in your breath to change the BTB?
___________________________
Note’s Review Q’s (use your notes/TB to answer the following)
7. Is lactic acid fermentation aerobic or anaerobic? ________________________
8.
Is cellular respiration aerobic or anaerobic? _______________________
9. How much ATP is produced by anaerobic processes (glycolysis)? (circle one) little
or
lot
10. How much ATP is produced by aerobic processes (Krebs/ETC)? (circle one) little
or
lot
11. Overall, explain what you observed in this lab.
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________