Name: _____________________
Oxygen Gas and Human Respiration
The process of breathing accomplishes two important tasks for the body. During inhalation,
oxygen-rich air is brought into your lungs. During exhalation, air depleted in oxygen and rich in
carbon dioxide is forced out. Oxygen is then transported to the cells where it is used in the
process of respiration, yielding carbon dioxide as a product.
C6H12O6 + 6 O2  6 CO2 + 6 H2O + energy
glucose
oxygen
carbon
dioxide
water
Gas exchange takes place in the lungs at the membrane between the alveoli and the pulmonary
capillaries. It is here that oxygen diffuses into the bloodstream and carbon dioxide diffuses out.
Under normal circumstances, there is an equilibrium between the oxygen and carbon dioxide
levels in the blood. Several mechanisms are involved in maintaining this balance. One such
mechanism involves chemoreceptors. These specialized cells respond to changes in carbon
dioxide, oxygen and H+ concentrations and influence the body’s ventilation patterns to maintain
the proper balance of blood gases.
In this experiment, you will determine what factors affect how long you can hold your breath.
You will be tested under two different conditions. The first condition is normal breathing. The
second condition is immediately following hyperventilation. Hyperventilation is when your
breathing rate is greater than what is necessary for proper exchange of oxygen and carbon
dioxide. This will be achieved by a period of rapid breathing prior to holding your breath.
OBJECTIVES
In this experiment, you will


Use an O2 Gas Sensor to determine residual oxygen levels in exhaled air.
Evaluate how internal O2 and CO2 concentrations influence breathing patterns.
MATERIALS
computer
Vernier LabQuest
Logger Pro
Vernier O2 Gas
Sensor
Biology with Computers
bio-chamber bottle
5 ½ rubber stopper
drinking straw
30 - 1
Experiment 30
PRELIMINARY QUESTIONS
1. How long do you think you can hold your breath?
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2. When you hold your breath, what do you think happens to the oxygen concentration in your
lungs? Explain why you think this.
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3. When you hold your breath, what do you think happens to the carbon dioxide concentration
in your lungs? Explain why you think this.
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4. The average person can hold his breath for a minute. What do you think prevents someone
from holding his breath for 2 or 3 minutes?
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PROCEDURE
Each person in a lab group will take turns being the subject and the tester. When it is your turn to
be the subject, your partner will be responsible for operating the equipment.
1. Lay the bio-chamber bottle on its side with the black rubber gasket on the top. Place the O2
Gas Sensor snuggly into the black rubber gasket of the bio-chamber bottle. Do not force it
into the hole too tightly. Keep the O2 Gas Sensor upright at all times.
2. Connect the O2 Gas Sensor to the Vernier LabQuest device.
3. Connect the Vernier LabQuest device to the laptop computer using the USB cable provided.
4. Open LoggerPro 3.8 from the Vernier Software folder in the Start menu.
5. Prepare the computer for data collection by opening the “30 Oxygen and Human Resp” file
in the Biology with Computers folder.
6. Insert the straw and stopper apparatus into the mouth of the bottle and position it so that a
student can comfortably blow air into the bottle.
30 - 2
Biology with Computers
Oxygen Gas and Human Respiration
7. When you begin collecting data, it is important that data collection begins at the same point
the subject begins to hold his breath.
a. Have a student take a deep breath and hold it. Immediately click
to begin data
collection. The student should hold his breath as long as possible.
b. When the student can no longer hold his breath, he should exhale into the straw
completely emptying his lungs, then quickly cover the straw with his finger. This should
result in the bio-chamber filling with the air the student was holding in his lungs. Allow
data collection to proceed for the full 120 seconds.
c. When data collection has finished, carefully remove the rubber stopper apparatus and the
O2 gas sensor (keeping it upright) and set it aside. Allow the condensation in the biochamber to evaporate and the sensor to return to a normal oxygen level. Leave everything
apart until you are prepared to collect data again.
d. Click the Examine button,
. The cursor will become a vertical line. As you move the
mouse pointer across the screen, the oxygen and time values corresponding to its position
will be displayed in the box at the upper-left corner of the graph. Scroll across the data to
determine how long the subject held his breath. Record the time in Table 1. Determine the
maximum and minimum oxygen concentrations and record them in Table 1. To remove
the examine box, click the upper-left corner of the box.
8. Move your data to a stored run. To do this, choose Store Latest Run from the Experiment
menu.
9. Reassemble the sensor, bio-chamber, and stopper-straw apparatus as before (Steps 1-6).
10. Collect data following mild hyperventilation. Have the same student take 10 quick deep
breaths, forcefully blowing out all air after each breath. The student should then take an 11th
breath and hold it. Immediately click
to begin data collection. The student should
hold his breath as long as possible. Follow Steps 7b-7d above.
11. Both runs should now be displayed on the same graph. Use the displayed graph and the data
in Table 1 to answer the questions on the next page.
DATA
Table 1: Oxygen in Exhaled Breath After Different Breathing Patterns
Breath
held
(s)
Maximum O2
concentration
(%)
Minimum O2
concentration
(%)
Change in
oxygen
(%)
Normal
Hyperventilation
Biology with Computers
30 - 3
Experiment 30
QUESTIONS
1. Did the amount of time the student held his breath change after hyperventilation (taking the
10 quick breaths)? If so, did the time increase or decrease? Explain why this might be so.
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2. In which trial (normal or hyperventilation) did the student exchange more oxygen between
his lungs and his body tissues? Why might this be the case?
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3. In which trial (normal or hyperventilation) was the concentration of oxygen in the lungs higher
at the end of the trial? Why might this be the case?
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4. On the first trial, what do you believe forced the student to start breathing again?
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5. On the second trial, what do you believe forced the student to start breathing again?
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6. Based on your answers to questions 4 and 5, does the concentration of oxygen or carbon
dioxide have a greater influence on how long one can hold his breath?
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30 - 4
Biology with Computers