PHOTOSYNTHESIS AND CELLULAR RESPIRATION LAB / 67

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1 PHOTOSYNTHESIS AND CELLULAR RESPIRATION LAB / 67 OBJECTIVE: (Copy or Summarize - 1pt) Students will directly observe the role of indicators in identifying the presence or lack of molecules or ions Students will directly observe the release of oxygen from plants during the process of photosynthesis in the form of bubbles. Students will observe a demonstration of the utilization of CO 2 in the water as it used during photosynthesis. Students will observe evidence/product of the effect of exercise. Students will analyze the affect of exercise on cellular respiration. Students will identify the role of carbon dioxide production, breathing rate, and heart rate in determining the rate of cellular respiration. BACKGROUND: Egeria densa, also known as Elodea densa because of its previously incorrect classification in the Elodea genus, is the most popular aquatic plant used to teach photosynthesis in the classroom. Originally from Brazil, E. densa has spread to temperate regions on all of the continents except Antarctica. Known for its bright green color and leafy stems, E. densa is an excellent oxygenating plant, making it perfect for use in freshwater aquaria and in the classroom. Cellular respiration is a chemical reaction that occurs in your cells to create energy; when you are exercising your muscle cells are creating ATP to contract. Cellular respiration requires oxygen (which is breathed in) and creates carbon dioxide (which is breathed out). This lab will address 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) and after 1 and 2 minutes of exercise. Breathing rate is measured in breaths per minute, heart rate in beats per minute, and carbon dioxide in the time it takes bromthymol blue to change color. Carbon dioxide production can be measured by breathing through a straw into a solution of bromthymol blue (BTB). BTB is an acid indicator; when it reacts with acid it turns from blue to yellow. When carbon dioxide reacts with water, a weak acid (carbonic acid) is formed (see chemical reaction below). The more carbon dioxide you breathe into the BTB solution, the faster it will change color to yellow. 6CO 2 + 6H 2 O à 6HCO 3 + 6H + PRE-LAB QUESTIONS: Use your prior knowledge, photosynthesis/cellular respiration notes or textbook to answer the following pre-lab questions. (Answer in notebook-1pt each) LAB PREP QUESTIONS: 1. What is a chemical indicator? 2. Why must we utilize the chemical indicator in the 2 labs? 3. Why must we have a control? 4. Why is it important to obtain more than 1 sample when collecting data?

2 PHOTOSYNTHESIS QUESTIONS: 5. What is the equation for Photosynthesis? 6. Which items are the reactants and products? 7. What is the essential molecule produced in photosynthesis? What is the by-product molecule (waste)? 8. In what part of the cell does Photosynthesis occur? 9. In the case of the photosynthesis lab, which gases are you observing? 10. In your opinion, which limiting factor will impact photosynthesis? Explain. CELLULAR RESPIRATION QUESTIONS: 11. What is the equation for cellular respiration? 12. Which items are the reactants and products? 13. What is the essential product produced in cellular respiration? What is (are) the byproduct (waste)? 14. In what part of the cell does cellular respiration occur? CONNECTING QUESTIONS: 15. Why do we balance equations in chemical equations? 16. Without photosynthesis, there is no cellular respiration and vice-versa. Explain. WRITE A PREDICTION/HYPOTHESIS of what do you expect to observe when you place the Elodea (Plant) into the jars? Make sure you EXPLAIN WHY you arrived at that conclusion. (Copy-1pt) WRITE A PREDICTION/HYPOTHESIS of how exercise will affect your body s production of carbon dioxide (i.e. do you think your body will produce more or less carbon dioxide as you exercise)? Make sure you EXPLAIN WHY you arrived at that conclusion. (Copy-1pt) Materials (Copy-1pt for each lab) Photosynthesis: Jar Elodea Plant Water BTB Cellular Respiration: Erlenmeyer Flask 250 ml Water Straw Procedures: (Copy or Summarize 1pt for each lab and/or set-up) Photosynthesis Procedures: 1. Fill a jar about 4/5 full of water. 2. Add 12 drops of Bromthymol blue. 3. Using a straw, blow gently into the jar #1 for 1 minute 4. In a day or two, the mixture in the test tube should change colors. Allow the color to change without altering the amount of water or BTB 5. Put a small of Elodea into the mixture. Make sure the plant is submerged. 6. Seal the Jar 7. Allow the jar to sit in the sun or under a light for 45 minutes. Make observations the next day. 8. Set-up Jar #2-5 with Different changes in the set-up 9. Jar #2 No Sun 10. Jar #3 Unsealed

3 11. Jar #4 2x amount of Elodea 12. Jar #5 2x amount of CO 2 in the water Cellular Respiration Procedures: PART A: Resting (no exercise) Measuring Carbon Dioxide Production: 1. Use a graduated cylinder to measure out 100 ml of tap water and pour it into a small beaker. 2. Use a dropper to add 8 drops of bromthymol blue to make a BTB solution. 3. Using a straw, exhale into the BTB solution. (CAUTION: DO NOT INHALE THE SOLUTION!!!!) 4. Time how long it takes for the blue solution to turn yellow. Record the time in Table Wash out the beaker repeat steps 1-4 twice more. 6. Average the results of the 3 trials. Record this in Table 1. Measuring Breathing Rate: 1. Count the number of breaths (1 breath = inhale + exhale) you take in 1 minute. Record this in 2. Table Repeat this 2 more times. 4. Average the 3 trials to get your average breathing rate. Record this in Table 2. Measuring Heart Rate: 1. While you calculate your breathing rate, have your partner take your pulse. 2. Count the number of beats in 30 seconds and multiply that number by 2. Record this in Table Repeat this 2 more times. 4. Average the 3 trials to get your average heart rate. Record this in Table 3. PART B: Increased Muscle Activity (Exercise) 1. Exercise for exactly 1 minute by doing jumping jacks. 2. While you are exercising, your partner should get the BTB solution ready as in Part A. 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 in Table Then quickly calculate your breathing and heart rates as you did before. You only need to do this once. 5. Record these values in Tables 2 & 3. Remake your BTB solution. 6. Exercise as you did before, but for 2 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 Then quickly calculate your breathing and heart rates as you did before. You only need to do this once. 9. Record these values in Tables 2 & If there is time, repeat the entire procedure for your lab partner. IF NOT, collect other data from other groups. Record data from 2 OR 3 other subjects in the class to get more data depending on if you partner was able to go or not

4 DATA/RESULTS: (COPY DATA TABLES) Photosynthesis Table (8pts) Jar Sealed (1pt) Drops of BTB(1pt) Duration of CO2 blown into jar (1pt) Original Color of Indicator (1pt) How many days to notice a change in BTB? (1pt) Last observed Color of Indicator (1pt) OBSERVATIONS. What influenced the results? Identify sources of error. (2pts) Cellular Respiration Table (5 points each table - 15pts)

5 Identify your subjects: First Name and Initial Last (1pts each) STUDENT 1: STUDENT 2: STUDENT 3: STUDENT 4: Conclusion Questions (15 points) Photosynthesis Conclusion Questions (Answer in notebook 1pt each unless stated otherwise) 1. What happened to the color of the mixture after you blew air into it? 2. What was in your breath that caused the color change? 3. Why did you put the Jars with Elodea in the mixture under light? 4. What did you observe in the Jars after the Elodea was under the light for several days? Without light? 5. Was there a difference in the rates of change for BTB in each jar. Account for each Jar (5 points) 6. How are the processes of photosynthesis in plants and cellular respiration in plants and animals related? Cellular Respiration Conclusion Questions (Answer in notebook 1pt each unless stated otherwise) 7. How did exercise affect the time needed for the solution to change color? Explain why the color change occurred (How does BTB work?) 8. What can you conclude about the effect of exercise on the amount of carbon dioxide that is present in your exhaled breath? Why is this so? 9. What can you conclude about the effect of exercise on breathing rate? Why is this so? 10. 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? 11. State whether your hypothesis was correct or incorrect and why. In doing so, discuss 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, as well as how the muscles cells get the energy needed to continue contracting.