Biology
Respiration Lab & Analysis
In answering the following questions try to provide your best “Biological”
explanations with detailed complete sentences.
1) Why do we need to breathe (please don’t answer “to Live”?
2) What kind of activities cause us to breathe harder?
3) Why would we need to breathe harder during some activities?
4) When we are running around or playing really hard we sometimes need to
stop and we feel “out of breath”. What does this feel like?
5) Why do you think this happens?
Biology
Respiration Lab & Analysis
BREATH OF LIFE
UNLOCKING THE SUGAR INSIDE OF YOU
Measuring the Differences in Carbon Dioxide Production
Background
Each cell of your body, including your muscle cells, gets energy from
a molecule called ATP, which functions like a rechargeable battery.
To recharge the ATP battery cells need to break down sugar.
All living cells (plants, bacteria, fungi, animals) can break down
sugar without oxygen in a process called Gylcolysis. Glucose
molecules are split into 2 smaller 3 carbon molecules called
pyruvate and a little ATP is produced.
Our cells require a lot of ATP. To meet the demand we call on mitochondria to combine
pyruvate with oxygen (which we breathe in) in a process called Aerobic Respiration (note:
plants and fungi do this as well). The result of this chemical reaction is carbon dioxide,
water, and a great deal of recharged ATP. Your body either uses or exhales the water, and
exhales all the carbon dioxide.
Occasionally we demand our muscles to use more ATP then our mitochondria can recharge
because the body can only supply oxygen so fast. To get extra ATP without oxygen cells can
break down pyruvate by fermentation (also called anaerobic respiration). Our body cells can
do this and release lactic acid (think about the muscle burn athletes feel) and a little ATP, but
no extra carbon dioxide. Yeast and bacteria can do this and release carbon dioxide, alcohol,
and a little ATP (fermentation, beer, wine, bread, etc).
When carbon dioxide enters water it makes the water more acidic. Bromthymol blue is a
chemical that changes color (blue to green) if exposed to acid. Using a Titration Technique
with sodium hydroxide (NaOH), you can compare the amount of carbon dioxide produced by
people at different levels of activity (after exhaling into a flask containing Bromthymol blue,
the more drops of sodium hydroxide needed to restore color, the greater the amount of carbon
dioxide in the flask).
In general a higher number of NaOH drops indicates better aerobic fitness. During exercise
it is important for the body to be able to quickly get rid of carbon dioxide.
Biology
Respiration Lab & Analysis
The Titration Technique:
Procedure:
1. Use a straw to exhale one complete breath of air into a flask
containing 25ml of bromthymol blue solution. The solution should turn
green, but if it does not, breathe additional breaths until it turns
green.
2. Return the solution to blue by adding drops of sodium hydroxide
(NaOH), one drop at a time swirling the flask between drops.
3. Swirl the flask after adding each drop to see if the color changes, as
sometimes the change is delayed.
4. Record the number of drops of NaOH. The more drops of sodium
hydroxide needed, the greater the amount of carbon dioxide in the
flask.
Brain Stretch!
1) What does bromthymol blue detect?:
2) What does NaOH (sodium hydroxide) indirectly measure?:
3) What does the amount of carbon dioxide a person exhales tell you about the rate of
respiration?
Biology
Respiration Lab & Analysis
4) Certain types of regular exercise cause an increase in the number of mitochondria
in muscle cells, making these cells able to generate more power. Which type of
activity, steady low intensity or fast high intensity exercise would most likely increase
the number of mitochondria? In your answer explain why an increase in mitochondria
would benefit the type of activity you chose.
5) Knowing that the heart is made of muscle, after a heart attack, small amounts of
lactic acid are present in the blood. What does this evidence suggest about the nature
of a heart attack? What would the relative amount of lactic acid let you know about
the heart attack?
Biology
Respiration Lab & Analysis
In this lab we will gather a range of date on human guinea pigs…ourselves 
Each student will gather baseline data on their aerobic fitness “at rest”
using NaOH as an indirect measure.
Students will then gather aerobic respiration data after 5 minutes of
running up and down flights of stairs.
Finally students will gather anaerobic respiration data after 30 seconds of
intense anaerobic activity (e.g. pull-ups, push-ups, one arm push-ups, etc.)
Personal Data to enter on our class spreadsheet
Question
Gender:
Answer
M
F
Body weight in pounds
Do you do sustained aerobic exercise 4 times or
more a week for at least an hour each time
(sustained running, dance, aerobics class,
swimming,etc.)
Do you do anaerobic or general exercise 4 times
or more a week for at least an hour each time
(basketball, football, lifting, etc.)
Do you eat Breakfast
Yes
No
Yes
No
Yes
No
Do you smoke regularly (1 or more cigarettes a
week)
Yes
No
At Rest Results:
Number of drops of sodium hydroxide used to
restore Bromthymol blue to it’s original color
Aerobic Exertion:
Number of drops of sodium hydroxide used to
restore Bromthymol blue to it’s original color
Anaerobic Exertion:
Number of drops of sodium hydroxide used to
restore Bromthymol blue to it’s original color
Biology
Respiration Lab & Analysis
Your Challenge!
Step 1) Develop a testable question that could be answered using the data
gathered from our class activity. Sample questions include:



Does gender make a difference in carbon dioxide produced during
exercise?
Does regular exercise have a significant effect on how effectively
carbon dioxide is removed?
How significant is the effect of smoking on aerobic fitness?
Your Question (you can use a sample question):
Step 2) As a team develop a hypothesis. Your hypothesis can take the form
of a prediction with an explanation, like the example below;
During exercise boys will produce more carbon dioxide than girls, because on
average boys have more muscle than girls, and will therefore burn more
sugar.
Our hypothesis:
Step 3) Looking at our class data and your question, what will serve as your
Control(s)
Independent Variable
Dependant Variable
Biology
Respiration Lab & Analysis
Step 4) Conduct a comparison analysis using the Respiration Data Base we
constructed on our class wiki. You might want to make a couple of
comparisons to refine your conclusions (i.e. “the effect of exercise is greater
then the difference between genders). Copy graphs you make to a MS Word
document.
Step 5) Compose a lab report using the lab report template. Remember to
include:
 Title with your names
 Intro paragraph stating your question and reasoned hypothesis
 The procedure you used during the experiment and how you
analyzed the data
 A Paragraph that explains your graph(s) and if your conclusions
are significant (as a rule of thumb a 20% difference is
significant)
 Paragraph that explains limitations of your analysis, and how the
activity has enriched/furthered your understanding.