Name Class Date. Explain how organisms get energy in the absence of oxygen. Identify the pathways the body uses to release energy during exercise.

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1 9.3 Fermentation Lesson Objectives Explain how organisms get energy in the absence of oxygen. Identify the pathways the body uses to release energy during exercise. Lesson Summary Fermentation Fermentation releases energy from food molecules by producing ATP without oxygen. Cells convert NADH to the electron carrier NAD +. This allows glycolysis to produce a steady stream of ATP. There are two forms of fermentation. Both start with the reactants pyruvic acid and NADH. alcoholic fermentation produces ethyl alcohol and carbon dioxide occurs in yeast and a few other microorganisms produces alcoholic beverages and causes bread dough to rise lactic acid fermentation produces lactic acid occurs in most organisms, including humans used to produce beverages such as buttermilk and foods such as cheese, yogurt, and pickles Energy and Exercise The body uses different pathways to release energy. For short, quick bursts of energy, the body uses ATP already in muscles as well as ATP made by lactic acid fermentation. For exercise longer than about 90 seconds, cellular respiration is the only way to continue generating a supply of ATP. Fermentation For Questions 1 6, write True if the statement is true. If the statement is false, change the underlined word or words to make the statement true. True 1. Glycolysis provides the pyruvic acid molecules used in fermentation. NAD + 2. Fermentation allows glycolysis to continue by providing the NADPH needed to accept high-energy electrons. anaerobic 3. Fermentation is an aerobic process. cytoplasm 4. Fermentation occurs in the mitochondria of cells. True 5. Alcoholic fermentation gives off carbon dioxide and is used in making bread. True 6. Most organisms perform fermentation using a chemical reaction that converts pyruvic acid to lactic acid. Lesson 9.3 Workbook A Copyright by Pearson Education, Inc., or its affiliates. All Rights Reserved. 137

2 7. Compare and contrast fermentation and cellular respiration by completing the compare/contrast table. Write your answers in the empty table cells. Aspect Fermentation Cellular Respiration Function produces ATP without oxygen long-term, large production of ATP Reactants glucose, ATP pyruvic acid, NADH glucose, ATP, pyruvic acid, NADH and FADH 2, oxygen Products NAD +, ethyl alcohol and CO 2 in alcoholic fermentation or lactic acid in lactic acid fermentation, ATP CO 2, H 2 O, ATP 8. Compare and contrast alcoholic fermentation and lactic acid fermentation by completing the compare/contrast table. Write your answers in the empty table cells. Type of Fermentation Alcoholic Summary Equation Pyruvic acid + NADH Alcohol + CO 2 + NAD + Use in Industry used to produce alcoholic beverages, causes bread dough to rise Lactic acid Pyruvic acid + NADH Lactic acid + NAD + used to produce cheese, yogurt, sour cream, pickles and other foods 9. What causes humans to become lactic acid fermenters? Brief periods without oxygen will cause many of the cells of a human body to produce ATP by lactic acid fermentation. Lesson 9.3 Workbook A Copyright by Pearson Education, Inc., or its affiliates. All Rights Reserved. 138

3 Energy and Exercise 10. What are three main sources of ATP available for human muscle cells? The three sources are ATP already in muscles, ATP made by lactic acid fermentation, and ATP produced by cellular respiration. 11. During a race, how do your muscle cells produce ATP after the store of ATP in muscles is used? After the ATP in muscles is used, the muscles produce ATP by lactic acid fermentation. 12. Why does a sprinter have an oxygen debt to repay after the race is over? Lactic acid fermentation produces lactic acid as a byproduct. The only way to get rid of the lactic acid is in a chemical pathway that requires extra oxygen. 13. A runner needs more energy for a longer race. How does the body generate the necessary ATP? Cellular respiration is the only way to continue generating a supply of ATP. 14. Why are aerobic forms of exercise so beneficial for weight control? The body stores energy in the form of glycogen. These stores of glycogen are usually enough for minutes of activity. After that, the body begins to break down other stored molecules, including fats, for energy. 15. Compare and contrast the role of fermentation and cellular respiration in the actual production of ATP. In your response, consider which process produces ATP and which process contributes to its production. For every molecule of glucose, cellular respiration produces 36 ATP molecules, while fermentation produces two ATP molecules. In fermentation, the two ATP molecules are produced during glycolysis. Fermentation supplies glycolysis with NAD + to keep it going. In cellular respiration, ATP is produced during glycolysis, the Krebs cycle, and the electron transport chain. Lesson 9.3 Workbook A Copyright by Pearson Education, Inc., or its affiliates. All Rights Reserved. 139

4 Chapter Vocabulary Review For Questions 1 7, match the term with its definition. Term F D C G A E B 1. anaerobic 2. glycolysis 3. Krebs cycle 4. calorie 5. matrix 6. aerobic 7. fermentation Definition A. Innermost compartment of a mitochondrion B. Process that forms either lactic acid or ethyl alcohol when no oxygen is present C. Stage of cellular respiration that starts with pyruvic acid and produces carbon dioxide D. Process in which glucose is broken down into two molecules of pyruvic acid E. In air F. Without air G. Amount of energy needed to raise the temperature of 1 gram of water 1 C For Questions 8 10, write the letter of the correct answer on the line at the left. A 8. Which is the process that releases energy by breaking down food molecules in the presence of oxygen? A. cellular respiration C. glycolysis B. electron transport D. photosynthesis C 9. Which is the electron carrier that accepts electrons during glycolysis? A. ADP C. NAD + C B. ATP D. NADP When comparing cellular respiration and photosynthesis, these two processes are best described as A. energy-releasing processes. C. opposite processes. B. energy-storing processes. D. similar processes. 11. Complete the illustration by adding the words aerobic or anaerobic on the lines provided. Glucose Glycolysis Energy anaerobic Krebs Cycle aerobic Energy CO 2 Electron Transport aerobic Energy O 2 H 2 O Chapter 9 Workbook A Copyright by Pearson Education, Inc., or its affiliates. All Rights Reserved. 140

5 DIVING WITHOUT A BREATH In the Chapter Mystery, you read about the traits that allow a whale to stay underwater for 45 minutes. The human body doesn t have any of those traits, so while swimming, we must stay near the surface where we have access to oxygen. Learning Does Carbon Sink? You have learned about the ways in which photosynthesis and cellular respiration are different. To put it simply, during respiration, animals and plants take in oxygen and release carbon dioxide and water; during photosynthesis, plants take in carbon dioxide and release oxygen. As you may already know, many human-made machines burn fossil fuels, such as coal and oil that release large quantities of carbon dioxide into the air. People began building carbonemitting machines in the mid-1700s when the Industrial Revolution began. More and more of them, including factories and cars, have been built ever since. As a result, much more carbon dioxide is being released into Earth s atmosphere than in the past. Carbon dioxide absorbs and retains heat near Earth s surface, and the additional carbon dioxide in the atmosphere contributes to global warming. Scientists and governments around the world are trying to find ways to reduce and eventually reverse global warming. This article presents one possible method for reducing carbon dioxide emissions to the atmosphere. We ll Try Everything Including Making New Carbon Sinks These days everyone is talking about reducing carbon dioxide emissions. Reducing carbon emissions is important. But we also could use a reliable way to dispose of the CO 2 we create. Nature does it every day, through carbon reservoirs, also known as carbon sinks. The word sink has many definitions, including something that stores or disposes of something else. In fact, Earth has two major types of carbon sinks: oceans and trees. The world s oceans absorb and store CO 2 from the air. All the world s plants take in carbon dioxide and release the oxygen we breathe. The catch is, these natural carbon sinks may not last. Studies indicate that oceans are reaching the limit of the carbon dioxide they can hold. And trees? Well, you ve probably heard how quickly we re cutting down rain forests. Perhaps people can make new carbon sinks. We ve been pumping oil and natural gas out of the ground for more than 150 years. What if we could pump CO 2 back into the ground to take their place? We have the technology to convert old oil and gas wells into carbon dioxide storage units that can hold the CO 2 we pump into them. It would be expensive to retrofit existing power plants, or to build pipelines to carry the gas away. But if we can find underground storage areas near fossil-fuel burning power plants, then transport would not be an issue. Also, building new carbon-disposal plants near power plants would be a relatively inexpensive way to store carbon emissions near their source. Continued on next page Chapter 9 Workbook A Copyright by Pearson Education, Inc., or its affiliates. All Rights Reserved. 141

6 Themes Science and Global Awareness 1. What are two main natural carbon sinks? The oceans and plants 2. What type of carbon sink does the author propose people use? An underground storage facility from which fossil fuels were previously removed 3. Most power plants are not located near sites where fossil fuels are mined. How do you think this would affect the practicality of this proposal? SAMPLE ANSWER: I think it will make the proposal less attractive because it will make extensive transportation of carbon dioxide emissions necessary. 4. According to the article, costs can be kept down if new plants are built in the right places. What are the right places? The right places are close to where carbon dioxide emissions are being created, such as power plants. 5. Do you think what the author proposes is a good long-term solution? Why or why not? SAMPLE ANSWER: I think it s not a good long-term solution because one day we ll run out of places on Earth to store the carbon dioxide, or because the gas may escape from its underground location. Planning a Carbon Sink The skills used in this activity include communication skills, creativity and intellectual curiosity, interpersonal and collaborative skills, accountability and adaptability, and social responsibility. What types of carbon sinks or carbon dioxide storage can be used to dispose of CO 2 in your community? Find out who in your local government is in charge of the trees on city property. Interview that person to identify places where trees could be planted. Can all new trees be planted in one place or must they be scattered around town? Get an estimate for the number of trees that might be planted on all sites in your community. Try to obtain as many trees as you can, either by asking local nurseries to donate them or by holding fundraisers to get the money to buy them. Then assemble a group of volunteers to spend Carbon Sink Day planting the trees. Make sure you get the necessary permits and oversight from your community government before you start planting. You might also have to prepare a plan for taking care of the small trees as they grow. Evaluate students projects based on the questions they prepare for their interview and the quality of the notes they take at the interview, the thoroughness and politeness of their request for tree donations, the creativity and organization of the fundraisers they hold, and the manner in which they cooperate with community officials in the planting and maintenance of the trees they plant. Chapter 9 Workbook A Copyright by Pearson Education, Inc., or its affiliates. All Rights Reserved. 142