Lab: The Effect of Exercise on Cellular Respiration Purpose: To analyze the effect the exercise has on breathing rate, heart rate, and carbon dioxide production Background Information: Cellular respiration is a chemical reaction that occurs in your cells to make energy. When you exercise, your muscle cells need energy in order to move your muscles. Cellular respiration requires oxygen (which is breathed in) and creates carbon dioxide (which is breathed out). The process of cellular respiration, which occurs in the cells, requires the respiratory system and the circulatory system. This lab will explore how exercise (increased muscle activity) affects the rate of cellular respiration. You will measure 3 different indicators of cellular respiration: breathing rate, heart rate, and carbon dioxide production. You will measure these indicators at rest (with no exercise); after one minute of exercise; and after two minutes of exercise. Breathing rate is measured in breaths per minute. Heart rate is measured in beats per minute. Carbon dioxide production is measured in the time it takes bromothymol blue (BTB) to change color. Carbon dioxide production can be measured by breathing through a straw into a solution of bromothymol blue (BTB). BTB is an acid indicator; when it reacts with acid it turns from a blue color to a yellow color. When carbon dioxide reacts with water, a weak acid is formed. The more carbon dioxide you breathe into the BTB solution, the faster it will change color from blue to yellow. Materials: Beaker Test tube of bromothymol blue (BTB) Dropper Cup Water Straw Stopwatch Lab Sheet
Procedure: Part 1: Resting (no exercise) Measuring Carbon Dioxide Production: 1. Use a small beaker to measure out 20 ml of tap water. Pour it into the cup. 2. Use a dropper to add 8 drops of bromothymol blue to make a BTB solution. 3. Using a straw, exhale gently into the BTB solution. (CAUTION: Do not inhale the solution! Do not breathe too hard, or you will spray BTB solution!) 4. Time how long it takes for the blue solution to turn yellow. Record the time in Table 1. 5. When you are finished, wash out the beaker. Measuring Breathing Rate: 1. Count the number of breaths (1 breath = inhale + exhale) you take in 30 seconds. Multiply this by 2 to get your breathing rate per minute. 2. Record your breathing rate in Table 2. Measuring Heart Rate: 1. While you calculate your breathing rate, have your partner take your pulse for 30 seconds. (See teacher if you do not know how to take a wrist pulse rate.) Multiply this by 2 to get your heart rate per minute. 2. Record your heart rate in Table 3. Part 2: Increased Muscle Activity (Exercise) 1. Prepare another BTB solution with 20 ml of water and 8 drops of BTB. Pour into the cup. 2. Exercise for exactly 1 (one) minute by doing jumping jacks. 3. After 1 minute of exercise, immediately exhale through the straw into the BTB solution. Time how long it takes for the BTB to turn yellow. Record this data in Table 1. 4. Then, quickly calculate your breathing and heart rates as you did before. Record these values in Tables 2 and 3. 5. Rinse your cup and then make a 3 rd BTB solution. 6. Exercise as you did before, but for 2 (two) continuous minutes. 7. Immediately exhale through the straw into the BTB solution. Time how long it takes for the BTB to turn yellow. Record this in Table 1. 8. Then, quickly calculate your breathing and heart rates as you did before. Record these values in Tables 2 and 3. 9. If you have time, repeat all steps with another lab partner. If you do not have time, collect data from 2 other groups.
Results: Table 1. Carbon Dioxide Production (time it takes BTB to change color) Resting sec sec sec sec Exercise: 1 minute sec sec sec sec Exercise: 2 minutes sec sec sec sec Table 2. Breathing Rate (breaths per minute) Resting /min /min /min /min Exercise: 1 minute /min /min /min /min Exercise: 2 minutes /min /min /min /min Table 3. Heart Rate (beats per minute) Resting /min /min /min /min Exercise: 1 minute /min /min /min /min Exercise: 2 minutes /min /min /min /min
Data Analysis: Using the grids below, graph your results (averages) on 3 bar graphs. Graph 1: Carbon Dioxide Production Graph 2: Breathing Rate Graph 3: Heart Rate
Conclusion & Reflection: Answer the questions below in COMPLETE sentences. 1. What can you conclude about the effect of exercise on breathing rate? Why is this so? Use your learning from science class to explain your answer. 2. What can you conclude about the effect of exercise on heart rate? Why is this so? What do your muscles need during exercise that the blood brings? Use your learning from science class to explain your answer. 3. Explain what you think is going on in the muscles of the body as muscle activity is increased. Address the need to get oxygen to the muscles and get rid of carbon dioxide. Use your learning from science class to explain your answer.