Activity Notes and Answers
Exploring Biology—The Products of Cellular Respiration
(BC Biology 12 student textbook page 178)
Curriculum Prescribed Learning Outcome and Achievement Indicators
• PLO B1 analyze the functional interrelationships of cell structures
• AI B1.1 describe the following cell structures and their functions: cell membrane;
cell wall; chloroplast; cytoskeleton; cytoplasm; Golgi bodies; lysosomes;
mitochondria; nucleus; ribosomes (polysomes); smooth and rough endoplasmic
reticulum; vacuoles; vesicles
• AI B1.1 state the balanced chemical equation for cellular respiration
Notes and Troubleshooting
• Review with the students the function of pH indicators.
• Discuss the reaction that takes place between carbon dioxide and water.
CO2 + H2O → H2CO3 → 2 H+ + CO32Point out that the reaction produces hydrogen ions, and that an excess of the ion
defines an acid.
• Suggest students blow into the straws in a normal manner for a fair test. After
exercising they will probably blow a little harder.
• When they are finished the activity, have students dispose of the contents of the
Erlenmeyer flasks in a safe, environmentally - friendly manner.
Expected Results
• The body produces carbon dioxide during cellular respiration. As students exercise
their rate of cellular respiration increases and consequently the amount of CO2
produced will increase. Carbon dioxide dissolves in water to form carbonic acid.
Bromothymol blue turns yellow in acidic solutions. When students exhale into the
bromothymol blue solution in the beaker, it will turn from blue to green to yellow
more rapidly after the student has been exercising.
Data Table
NAME
Flask A
Time taken for
bromothymol blue to turn
yellow before exercise
(min)
Flask B
Time taken for
bromothymol blue to turn
yellow after exercise
(min)
6-14 MHR TR • Unit A Cell Biology
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Answers to Questions
1. The bromothymol blue in the Erlenmeyer flask turns green then yellow when
the student blows into it. The CO2 in the student’s breath mixes with the water in
the bromothymol blue solution forming an acid.
2. When the CO2 in the student’s breath is mixed with the water in the Erlenmeyer
flask they form carbonic acid, H2CO3. This dissociates into H+ ions and CO32ions. The H+ ion contributes to the acidic nature of the solution.
C6 Activity Notes and Answers
3. The exercise done by the student causes the solution in the flask to turn yellow
more quickly. The time taken to change colour is shorter.
4. The process is cellular respiration.
The word equation is glucose + oxygen → carbon dioxide + water + ATP
The balanced chemical equation is: C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP
5. Cellular respiration occurs in the mitochondria.
6. During exercise your body required more ATP for the activity. As a result
more cellular respiration occurred than when at rest and more carbon dioxide
was produced.
7. a. The pH indicator in the beaker would gradually change from blue to yellow
as the solution absorbs carbon dioxide from the air. The carbon dioxide in the
room is a result of the mitochondria in the students’ cells performing cellular
respiration and producing CO2. The blood carries the CO2 to the lungs where
it is exhaled into the classroom.
b. During the day, the pH indicator in the beaker would change from blue to
yellow more slowly or it may not change colour. The plants are undergoing
cellular respiration, but some of the CO2 they produce is being used for
photosynthesis. At night the pH indicator in the beaker would change from
blue to yellow more quickly. The plants are undergoing cellular respiration
producing CO2. No photosynthesis occurs in the dark, so no CO2 will be
removed from the air in the room by the plants at night.
Chapter 6 Cellular Respiration • MHR TR
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