Biology Cellular Respiration Neatly answer all questions completely for credit. Show all work.

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1 Teacher Notes Time: 45 minutes (plus 15 minutes for teacher preparation over two days) Student Difficult: moderate Purpose: Investigate cellular respiration in dormant and germinated seeds Overview: Students will compare the relative volume of oxygen used by dormant and germinated seeds. They will: prepare test-tube respirometers with dormant and germinated seeds measure the height of water that rises in the test tubes in response to the partial vacuum created by oxygen being consumed Lab Preparation: Use large, fresh seeds (peas or beans). Soak the seeds for hours. Lab Management: Remind students that respiration uses O 2 and forms CO 2. The pressure due to CO 2 might cancel out any change due to the take-up of O 2. To solve this problem, potassium hydroxide is added to combine with CO 2 to form insoluble potassium carbonate. Do not to remove the tubes from the beaker while measuring water height. Students should measure the height of the water in the tubes after inverting them and again the next day. Calculate any differences in height, if any. Setups should be stored at room temperature overnight. Post-Lab Discussion: Discuss the change in volume of gas in the tubes as indicative of the amount of O 2 consumed. Ask, Why did water move up into the tube? Water rises due to the partial vacuum created by oxygen consumption. Answers: Analyze and Conclude 1) A bar graph is best; check students work. 2) Oxygen consumption was measured by the height of the water in the tubes. Water level in the tube with germinated seeds was greater than that in the tube with dormant seeds. Dormant seeds respire very slowly. 3) Tube 3 is a control. It may show a slight rise in water level due to atmospheric pressure changes. 4) The volume of gas and corresponding air pressure in the test tubes decreased with increasing cellular respiration, that is, with increasing consumption of O 2. 5) Water level would be higher after one day. After one week, the germinated seeds may die because there is no CO 2 in the tube for photosynthesis. Cells and Energy 1 Overview of Cellular Respiration

2 Cellular Respiration Plant cells use cellular respiration to make ATP from the sugars they produce during photosynthesis. During cellular respiration, carbon dioxide (CO 2 ) is formed as oxygen (O 2 ) is used. In this experiment, you will compare cellular respiration rates in dormant (dry) and germinated (pre-soaked) seeds. Problem: How do respiration rates compare in dormant and germinated seeds? Process Skills: Materials: Procedure: Measuring Graphing Collecting Data Analyzing Data 3 test tubes marking pen 6 pre-soaked seeds 6 dry seeds 6 cotton plugs 1.5 teaspoons potassium hydroxide (KOH) powder rubber band 100-mL beaker 25-mL colored water metric ruler 1) Label the three test tubes as the following: a. Tube 1: pre-soaked seeds; Tube 2: dry seeds; Tube 3: no seeds 2) Layer into the test tubes the following materials. Be sure that the layers of materials are compact, but not too tight. a. Tube 1: pre-soaked seeds, cotton plug, 1/2 tsp. potassium hydroxide, cotton plug b. Tube 2: dry seeds, cotton plug, 1/2 tsp. potassium hydroxide, cotton plug c. Tube 3: cotton plug, 1/2 tsp. potassium hydroxide, cotton plug d. Caution: Potassium hydroxide is a strong base; avoid contact with eyes, skin, and clothing. 3) Use the rubber band to hold the three test tubes together. 4) Pour the 25 ml of colored water into the beaker. Cells and Energy 2 Overview of Cellular Respiration

3 5) Invert the tubes and place them in the beaker as shown below. Wait 15 minutes. 6) Using a ruler, measure the distance (in cm) that the colored water travels up each of the three test tubes. a. Record your results is the table below. TABLE 1. CELLULAR RESPIRATION IN DORMANT AND GERMINATED SEEDS Test Tube Distance Colored Water Travels (cm) 1. pre-soaked seeds 2. dry seeds 3. no seeds Cells and Energy 3 Overview of Cellular Respiration

4 Analyze and Conclude 1) Analyze Choose the type of graph that best represents the data. Construct your graph. 2) Analyze Describe your observations and measurements of test tubes 1 and 2. What do the data show? Explain why differences between the two tubes might exist. Cells and Energy 4 Overview of Cellular Respiration

5 3) Evaluate What is the function of test tube 3 in the experiment? What do the measurements from this test tube demonstrate? 4) Infer Potassium hydroxide reacts with, and removes, carbon dioxide from the air. Why might cellular respiration be responsible for water rising into some of the test tubes? 5) Apply Suppose this experiment were allowed to run an additional day. What might you expect to encounter? What about after a week? Cells and Energy 5 Overview of Cellular Respiration