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Mr. Orend Honors Biology
Cellular Respiration
How does exercise affect disposal of wastes from cellular respiration?
BACKGROUND INFORMATION
Cellular respiration refers to the cellular process of harvesting energy from food molecules in aerobic (in the
presence of oxygen) conditions. This process occurs in the mitochondria. All eukaryotic cells have
mitochondria, including plants. During cellular respiration, food molecules are burned to release chemical
energy stored in their chemical bonds. This energy is then stored by the cell in the chemical bonds of
adenosine triphosphate (ATP).
Unfortunately, cells are not totally efficient at harnessing the energy released from food molecules. For
example, only 40% of the energy of a glucose molecule is converted to energy in ATP. The rest is converted to
heat. Glucose (C6H12O6) is often used as a convenient representative food molecule, but cells also burn many
other organic molecules in cellular respiration. The chemical equation for the burning of glucose through
cellular respiration is shown below.
The human body, and all other organisms on Earth, uses energy from ATP for all of its activities. Our body
cells require a continuous supply of energy just to stay alive-to keep the heart pumping blood, to breath, to
maintain body temperature, and to digest food. These and other life-sustaining activities use as much as 75% of
the energy a person takes in as food during a typical day. Above and beyond the energy we need for body
maintenance, the ATP made during cellular respiration provides energy for voluntary activities. This includes
dancing, bicycling, bowling, running, hopscotching, swimming, playing piano, and doing the Macarena ().
PURPOSE: The purpose of this experiment is to determine whether or not exercise will affect the amount of
carbon dioxide an organism will produce. The investigators will test two different humans before and after
exercise to determine the difference in the waste products produced.
PRE-LAB QUESTIONS
1. From what molecule does the carbon in the carbon dioxide produced cellular respiration come?
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2. The glucose consumed by heterotrophs is originally synthesized during what process in autotrophs? In which
step of this process is glucose ultimately produced?
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3. What do you notice about the equation for cellular respiration when compared with photosynthesis?
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4. Is cellular respiration an endergonic or exergonic process? What molecule stores this energy in the cell?
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5. Cellular respiration occurs in the mitochondria. Plants perform cellular respiration in mitochondria just as
animals and humans do. Why do plants need to perform cellular respiration?
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6. What would happen if the test subject was enclosed in a jar during this experiment?!?! From your knowledge
of the equation for cellular respiration, why would this happen?
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7. What type of everyday substances have carbon dioxide dissolved in them? Are these substances generally
acidic or basic?
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8. Why would you want to test more than one human in this experiment?
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9. During this experiment you will measure the amount of carbon dioxide produced before and after exercise.
Write your hypothesis for this experiment below. (If…then…because…)
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MATERIALSs:
2 small test tubes
10 mL graduated cylinder
2 straws
Goggles
Pen or pencil
Masking tape
Bromthymol blue solution (an indicator of acids)
Timer
Test tube rack
250 mL beaker of water
SAFETY PRECAUTIONS:
*****All students MUST be wearing an apron and safety goggles!!!!!!
*****Make sure you DO NOT inhale through the straw during testing!!!!!!
PROCEDURE
1. Label two test tubes A and B. Place them in the test tube rack.
2. Put 10 mL of water (measure this with your graduated cylinder-be sure to measure the level at the meniscus)
and 10 drops of Bromothymol blue solution (an acid/base indicator) in each test tube.
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Carbon dioxide causes Bromothymol blue to turn yellow or green in the presence of an acid.
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Our external respiration (breathing, specifically exhalation) releases the waste products from
cellular respiration, carbon dioxide and water.
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The mixture of carbon dioxide and water produces a substances known as carbonic acid.
3. One member of the group will time this step using the timer. When they say “GO” they will start the
timer, while another member of the group will SLOWLY blow air through a straw into the bottom of test tube
A.
DO NOT inhale through the straw!
4. When the solution changes color to yellow or green, the timer should say “STOP,” and then record on the
data chart how long the color change took.
5. The same test subject will then jog in place for one minute while the timer times them.
Please let your teacher know if you feel faint or dizzy, or have any medical
condition that would prohibit you from doing this.
6. Once the subject has completed the exercise have them immediately blow into the straw, this time into the
bottom of test tube B. The timer should start the time when they begin blowing and stop when the color
changes. Also record these results on your data chart.
7. Switch roles with another member of the group and REPEAT steps 2-6.
DATA CHART- Make sure to record your date in SECONDS.
Before Exercise
Test Tube A
Subject #1
Subject #2
After Exercise
Test Tube B
Difference in Time for
Color Change
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Cellular Respiration Post-Lab
PART TWO: **************DO NOT THROW AWAY YOUR TEST TUBES!!!!!!*****************
Before answering the questions below, you will conduct a second phase to this experiment to be analyzed
tomorrow when you come in.
DIRECTIONS:
1. Obtain 2 small sections of aquatic plant or algae about 2 cm long. Place one section in test tube A, and
one section in test tube B.
2. Label your test tubes with your group names using masking tape and a permanent marker.
3. Put your test tubes in the test tube rack on the window sill until tomorrow.
DATA ANALYSIS: Look at your data and explain the results obtained during the experiment. USE your
numbers in your response.
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CONCLUSION: Answer the following questions using complete sentences.
1. How did exercise affect the time for the solution to change color? Did these results support your hypothesis?
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2. What process in your body produces carbon dioxide? How does exercise affect this process? Why do you
think this is the case?
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3. Breathing into the water produced a color change in the Bromothymol blue solution. What does this color
change indicate? What substance was produced when your breath mixed with the water?
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4. EXPLAIN. Describe how exercise affects your INTERNAL respiration rate (cellular respiration) and
therefore your EXTERNAL respiration rate (breathing). (At LEAST 3 complete sentences!)
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5. ERRORS What errors could have occurred throughout the completion of this lab? What might you do
differently if you were to conduct this experiment again?
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6. How do you expect the algae or aquatic plant to affect the color of your solution? What compounds do you
expect to be used up/produced by the aquatic plant or algae? Why?
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7. Where in the cell does the carbon dioxide produced during cellular respiration occur? Do plants also have
this organelle? What organelle is responsible for the color change that occurred overnight from the plants?
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8. What do you think would happen to the solution if you were to capture the gas escaping from a burning
candle and perform the same experiment? Why?
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9. What do you think would happen to the solution if you were to capture the gas escaping from a burning
candle and perform the same experiment? Why?
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