How does Exercise Affect Cellular Respiration?
Introduction:
Cellular respiration takes stored energy in glucose and converts it into usable energy in the form of ATP. Cellular
respiration is an aerobic process meaning it requires oxygen to occur. Oxygen is going to combine with carbon molecules
from the glucose to form carbon dioxide as glucose is converted to ATP. Oxygen and glucose, therefore, are reactants while
carbon dioxide, water, and energy are products. In this lab, we are going to investigate the effects of exercise on the rate of
cellular respiration. Again there are two ways to measure the rate of a chemical reaction. One way is to measure the
amount of raw material used, and the other is to measure the amount of product produced. In this experiment, we will
measure the amount of carbon dioxide produced using an indicator.
The indicator used in this experiment is called bromothymol blue. Bromothymol blue indicates changes in pH of an
environment. The indicator will be blue in basic and neutral environments and yellow to yellowish-green in acid
environments. When carbon interacts with water it creates carbonic acid:
H20 + CO2  H2CO3  H+ + HCO3-
Materials:
Two beakers
Graduated cylinder
Bromothymol blue
Goggles
Beakers
Straws
Procedure:
1. Go to the back room and obtain goggles. You can leave them on the lab desk until instructed to put them on.
2. At your lab table two beakers will be labeled A and B. Measure 10 ml of water and add 2-3 drops of
bromothymol blue to each test tube.
3. PUT ON GOGGLES!
4. Using the stop watch, time this step. When your partner says go, slowly blow air through a straw into the
bottom of the test tube.
5. When the solution changes color to yellow, the timer will say stop and record the time it took for the
solution to changes color.
6. Using the stop watch as a timer, jog in place for 1 minute.
7. When you are done repeat steps 4-6 including – PUTTING ON GOGGLES!
8. Compare times and answer questions.
Pre-Lab Questions:
1. How is carbon dioxide linked to exercise?
2. How will exercise affect your body’s production of carbon dioxide?
3. Bromothymol blue indicates ________________________________.
a. It turns _________________ in ___________________ environments.
b. It turns _________________ in ___________________ environments.
4. The addition of carbon dioxide to an environment will cause the environment to become _____________.
Post-Lab Questions:
1. How long did it take to turn without exercise?
a. With exercise?
2. How did exercise affect the time for the solution to change color?
3. What is the process in your body that produces carbon dioxide called?
4. Was your hypothesis correct? Explain your answer.
Cellular Respiration
True or False
_____ 1. Cellular respiration that proceeds in the presence of oxygen is called aerobic respiration.
_____ 2. Oxygen is the final electron acceptor during anaerobic respiration.
_____ 3. Cellular respiration begins with the absorption of sunlight by the mitochondria photosystems.
_____ 4. Cellular respiration occurs in the mitochondria.
_____ 5. Mitochondria posses their own DNA and ribosomes
_____ 6.The Krebs cycle comes after glycolysis, during cellular respiration.
_____ 7. ATP synthase uses electrons to make ATP molecules.
_____ 8. One molecule of glucose holds enough energy to produce an average of 30 ATP.
_____ 9. The Krebs cycle produces four ATP.
_____ 10. Whereas plants perform photosynthesis, plants and animals perform cellular respiration.
_____ 11. Aerobic respiration evolved prior to anaerobic respiration.
Cellular Respiration Stage III: Electron Transport
Transporting Electrons
High-energy electrons are released from electron carriers, and they move along electron transport chains. The electron
transport chains are on the inner membrane of the mitochondrion. As the high-energy electrons are transported along the
chains, some of their energy is captured. This energy is used to pump hydrogen ions (from NADH and FADH2) across the
inner membrane, from the matrix into the intermembrane space. ATP synthase acts as a channel protein, helping the
hydrogen ions cross the membrane. It also acts as an enzyme, forming ATP from ADP and inorganic phosphate. After
passing through the electron-transport chain, the “spent” electrons combine with oxygen to form water. This is why
oxygen is needed; in the absence of oxygen, this process cannot occur.
How Much ATP?
You have seen how the three stages of aerobic respiration use the energy in glucose to make ATP. How much ATP is
produced in all three stages? Glycolysis produces 2 ATP molecules, and the Krebs cycle produces 2 more. Electron
transport begins with several molecules of NADH and FADH2 from the Krebs cycle and transfers their energy into as
many as 34 more ATP molecules. All told, then, up to 38 molecules of ATP can be produced from just one molecule of
glucose in the process of aerobic respiration.
Questions
1. Where does electron transport get its energy during cellular respiration?
2. What is the role of the electron transport chain in cellular respiration?
3. Why is the role of oxygen in cellular respiration?
4. Describe ATP synthase and its role.
5. Summarize how up to 36 molecules of ATP are produced for each glucose molecule.