Name_________________________
Date: ________________ Period:___
Cellular Respiration Lab
Purpose: to investigate how we can use what we breathe to measure what is happening
inside of our body cells
Pre-Lab Questions:
1. What goes INTO the reaction (reactants) that transforms food into energy within our
cells? *Circle all that apply
a.
b.
c.
d.
e.
Carbon dioxide
Water
Oxygen
Sugars (glucose)
Energy (ATP)
2. What is PRODUCED (products) by the reaction that transforms food into energy within
our cells? *Check all that apply
a.
b.
c.
d.
e.
Carbon dioxide
Water
Oxygen
Sugars (glucose)
Energy (ATP)
3. Write down the reaction for CELLULAR RESPIRATION
4. What is the main purpose of cellular respiration?
5. How are cellular respiration and photosynthesis alike? How are they different?
6. Why do we need to breathe (don’t answer: “to live”)?
Some Important Background for Lab:
Bromothymol Blue Indicator Reaction to Measure CO2
● When carbon dioxide enters water it makes the water more acidic. Bromothymol blue is a chemical
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Name_________________________
Date: ________________ Period:___
that changes color (blue to green) if exposed to acid. In other words, Bromothymol Blue will change
colors (blue to green) when CO2 is present because CO2 converts to an acid in the presence of
water. Using the Titration Technique described below, you can compare the amount of carbon
dioxide produced by people at different levels of activity.
The Titration Technique Procedure to Indirectly Measure CO2:
● Use a straw to exhale air into a flask containing a solution of Bromothymol blue.
● Add 1 drop of sodium hydroxide (NaOH) to green Bromothymol Blue
● Swirl flask for up to 30 to 60 seconds to make sure color change is permanent
● If solution has not returned to its original royal blue color, then add 1 more drop of NaOH and
swirl flask again
● Repeat adding 1 drop at a time until the solution returns to its original royal blue color even after
rigorous, prolonged swirling of flask
● The more drops of sodium hydroxide needed, the greater the amount of carbon dioxide in the
flask.
Experiment
Lab Roles in each group of 3:
● 1 person will be in charge of adding the drops for titration, timing the subjects , and recording the
data in the lab data entry forms on the website.
● The other 2 people will be the subjects who perform activities 1 and 2 below and measure the
other subject’s respiratory rate. Also they will assist in the titration process by helping determine
when the Bromothymol Blue has been restored to its original blue color completely.
Activity #1: At rest
1. Measure the respiration (breathing) rates (RR) of each subject by counting how many breaths they
take normally over 15 seconds and multiplying by 4 for # of breaths per one minute. Record in data
table.
2. Pour 75 mL of Bromothymol Blue solution into the flask you will be using.
3. Using a clean straw and while fully rested, blow into the flask for 10 seconds.
4. Using the NaOH, titrate the solution to determine the amount of CO2 present and record in your
data table.
5. Dump your Bromothymol Blue Solution, rinse out the flask and refill flask with 75 mL fresh
Bromothymol Blue from teacher solution.
Activity #2: Perform jumping jacks for 30 seconds at comfortable, steady pace (meaning if
you cannot continue talking with your group while doing jumping jacks, then you should slow
down your pace so that you can talk and jack at the same time comfortably)
6. At the completion of 30 seconds of comfortable jumping jacks, subject will immediately blow into
the flask Bromothymol Blue solution with the same straw for 10 seconds.
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Name_________________________
Date: ________________ Period:___
7. Again, also get the respiration rate of subject immediately after exercise and record. in data table
8. Titrate the green solution NaOH until it turns blue and record # of drops in data table.
At End of Lab
9. Clean up the flasks and beakers, throw out the straws, and return all equipment to your station dry.
10. Answer the post-lab questions.
Data Table:
Subject Name
#Drops NaOH
(CO2) at rest
#Drops NaOH
(CO2) after
jumping jacks
Respiratory Rate
per 1 minute
(O2) at reat
Respiratory Rate
per 1 minute
(O2) after
jumping jacks
Post-Lab Questions:
What conclusion can you draw from the class data about how carbon dioxide output
changes during aerobic activity from jumping jacks compared to at rest? *Assume # drops
of NaOH measures carbon dioxide output
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a.
b.
c.
d.
Name_________________________
Date: ________________ Period:___
CO2 output decreases with aerobic activity compared to rest
CO2 output increases with aerobic activity compared to rest
CO2 output stays the same with aerobic activity compared to rest
CO2 output is not a factor during aerobic activity
Based on the lab results, what PRODUCT of cellular respiration done by our muscle cells
were we able to indirectly measure? Choose BEST answer only
a.
b.
c.
d.
e.
Carbon Dioxide
Water
Oxygen
Sugars (Glucose)
Energy (ATP)
Based on the lab results, what REACTANT of cell respiration done by our muscle cells
were we able to indirectly measure? *Choose BEST answer only
a.
b.
c.
d.
e.
Carbon Dioxide
Water
Oxygen
Sugars (Glucose)
Energy (ATP)
If you are told that the chemical equation for cellular respiration is: C6H12O6 + O2 -->
CO2 + H2O + ATP, what can you infer about the levels of the other reactants and products
if CO2 levels increased? *
a.
b.
c.
d.
e.
The reactants increased, but the products stayed the same
The reactants decreased, but the reactants increased
The reactants increased, but the products decreased
The reactants increased and the products increased
The other reactants and products were unchanged
What does the amount of O2 intake and CO2 output tell us about what is happening inside
our bodies' cells in terms of energy being converted from food (in other words, the rate
of cellular respiration in our cells)? *
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Name_________________________
Date: ________________ Period:___
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