Reader: _________________________________
Honors Biology
Recorder: _________________________________
Ch. 9- Cellular Respiration
Experimenter: _________________________________
Date: _________________________ Period:_________
Introduction
Life needs energy! The cells in our bodies need energy to function and to be, simply, alive.
Recall that cellular respiration and photosynthesis are two processes that allow plants and animals to live. Plants can make their own food (glucose) and make oxygen using the energy from the sun. This is photosynthesis. Animals and plants have to break down molecules like glucose to make ATP, which cells can use for energy. This is cellular respiration, which uses oxygen and glucose, and makes carbon dioxide.
Bromothylmol blue is an indicator for pH. When no carbon dioxide (CO
2
) is present, the pH is high and bromothymol blue is blue. When carbon dioxide (CO
2
) is present, the pH is low, and the bromothymol blue turns yellow.
Fill in the equation for cellular respiration below: (5 pts)
Question
6_______________ + _______________  6_______________ + 6_______________ + 38_______________
Does cellular respiration occur faster with or without exercise?
Hypothesis (2 pts)
Include an explanation why you think it does/does not.
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Materials
 Test tube
 Water
 Graduated cylinder
 Straw



Bromothymol Blue solution
Stop watch
Pen/pencil
Safety Precations
 DO NOT inhale through the straw.
If your skin comes into contact with the solution, notify Ms. Nguyen and wipe away with water.
 If you become dizzy or light-headed during the lab, notify Ms. Nguyen and sit down immediately.
Procedure
Set-up:
1.
Obtain a clean test tube & fill with 5 ml of water using the graduated cylinder.
2.
Add two drops of bromothymol blue to the test tube.
Without exercise:
3.
GENTLY blow bubbles into the test tube using the straw. Time how long it takes to change the solution from blue to yellow and record this on the data table.
4.
Rinse out the test tube with water and save the straw.

With exercise:
5.
Using the same test tube (now clean) fill with 5 ml of water and add 2 drops bromothymol blue.
6.
Do jumping jacks for 30 seconds. GENTLY blow bubbles into the test tube. Breathe at the same rate as you did in step 3. Time how long it takes to change to yellow and record this in the data table.
7.
Rinse out the test tube with water and save the straw.
8.
Using the same test tube (now clean) fill with 5 ml of water and add 2 drops bromothymol blue.
9.
Do jumping jacks for 2 minutes. GENTLY blow bubbles into the test tube. Breathe at the same rate as you did in step 3. Time how long it takes to change to yellow and record this in the data table.
Clean-up:
10.
Rinse out the test tube and wipe down your lab bench.
11.
Throw away the straw and any paper towels.
Data (3 pts)
Time of exercise Time for solution to change color (seconds)
0 seconds
30 seconds
2 min
Graph (5 pts)
Create a bar graph that illustrates the relationship between the time it takes for the color of the bromothymol blue to change color before and after exercise. The Y-axis should be the time for the color change to occur and the X-axis should be the time of exercise. Your graph must include:
 A title that clearly indicates what the graph is representing
 Labeled X and Y axes (with units!)
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Conclusion
1.
Identify the dependent and independent variables in this lab. (2 pts)
2.
Which byproduct of cellular respiration caused the color of the bromothymol blue to change? (1 pt)
3.
Did this test indicate that you produce more or less carbon dioxide after exercising? Use your data to explain. (2 pts)
4.
Which reactant of cellular respiration does your body need in order for cells to respire and make carbon dioxide, water and ATP? (1 pt)
5.
Did you notice during exercise that your body needed more oxygen to produce energy? How does your body compensate for that? (2 pts)