Name: ____________________ Cellular Respiration Lab Learning Outcomes: · Compare cellular respiration and photosynthesis in Elodea under different environmental conditions · Observe anaerobic...

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Name: ____________________ Cellular Respiration Lab Learning Outcomes: · Compare cellular respiration and photosynthesis in Elodea under different environmental conditions · Observe anaerobic respiration in yeast Introduction Cellular Respiration All living organisms use cellular respiration to provide the energy used for the many processes involved in maintenance and growth. The process of cellular respiration includes several steps beginning with glycolysis and concluding with either fermentation or the electron transport chain (ETC). To obtain energy from glucose, all cells perform several reactions involving the transfer of electrons and/or hydrogen atoms. Reactions of this type are known as oxidation/reduction reactions. An easy way to remember what occurs in these reactions is OILRIG: Oxidation Is Losing electrons/hydrogens and Reduction Is Gaining electrons/hydrogens. The initial use of glucose occurs in the cytoplasm of the cell and involves oxidation/reduction reactions and molecular rearrangements, resulting in two molecules of pyruvic acid, two molecules of ATP and two molecules of reduced coenzyme, NADH + H+ This series of reactions is known as glycolysis and since the presence of oxygen has not been required, the process is considered anaerobic. Under anaerobic conditions, the pyruvic acid produced by glycolysis may participate in fermentation where hydrogens/electrons are removed from NADH and are accepted by pyruvic acid to make either lactic acid or ethanol. The type of creature determines whether lactic acid or ethanol is produced. For example, yeast contain the enzymes for ethanol production while humans contain the enzymes for lactic acid production. The importance of fermentation to the cell is its reoxidation of NADH to NAD+, which is used to keep glycolysis going so that small amounts of ATP can be produced in the absence of oxygen. Under aerobic conditions where oxygen is available, pyruvic acid may enter into a series of reactions involving the Krebs Cycle (Citric Acid Cycle) and the Electron Transport Chain, which produces approximately 36 ATP per glucose if the cell is operating at highest efficiency. EXPERIMENT 1: COMPARISON OF PHOTOSYNTHESIS AND CELLULAR RESPIRATION IN ELODEA 1. What was the purpose of phenol red in this experiment? __________________ 2. What was the color of the tube with the plant in the light after the experiment? _____________________ a. Does this indicate an acidic or a basic solution? ___________________________________________ b. Explain the observed color change with respect to the change in CO2 concentration. Was the plant performing cellular respiration or photosynthesis more? 3. What was the color of the tube with the plant in the dark after the experiment? ________________ a. Does this indicate an acidic or a basic solution? ______________________________________ b. Explain the observed color change with respect to the change in CO2 concentration. Was the plant performing cellular respiration or photosynthesis more? 4. The two products of cell respiration (also known as aerobic respiration) are carbon dioxide and water. As an animal, you release carbon dioxide to the atmosphere. What do plants do with this carbon dioxide? EXPERIMENT 2: FERMENTATION IN YEAST Table 1: Record observations of the three bottles in terms of the size of the balloon used to seal each bottle. Feel free to include other descriptions as well. Time Flask 1. 10 g Glucose Flask 2. No Sugar 0 minutes 20 minutes 1. What is the difference between aerobic and anaerobic respiration? 2. What are the products of alcohol fermentation performed by yeast? 3. What is the purpose of Flask #2 “No sugar?” 4. Which tube showed the fastest/greatest inflation of the balloon? Explain why. 5. How might running this experiment with ice water (instead of warm water) affect the results? Why? 6. Based on the information above, circle or highlight the correct answers in the following statement about yeast. The first one has been done for you. Yeast are microbes that provide the neutrons / enzymes (circle or highlight one) needed to break down sugars in the process of alcohol / lactic acid (circle or highlight one) fermentation. This happens in an aerobic / anaerobic (circle or highlight one) environment with the final products produced being CO2 and ethanol / lactic acid (circle or highlight one).