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11141 ~ [F ~F JJ~ P IF F li~~ ~ :~F 1 ~iti~f~ ;1 FF~ If ii Name Class Date Chapter 9 Summary Cellular Respiration 9-i Chemica Pathways Food is the energy source for cells.

1 11141 ~ [F ~F JJ~ P IF F li~~ ~ :~F 1 ~iti~f~ ;1 FF~ If ii Name Class Date Chapter 9 Summary Cellular Respiration 9-i Chemica Pathways Food is the energy source for cells. The energy in food is measured in calories. A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius. The Calorie (capital C) used on food labels is equal to 1000 calories. Cells do not burn glucose or other food compounds. They gradually rel?ase thç energy. The process begins with a pathway called glycolysis. Glycolysis is the process in which a glucose molecule is split in half. This forms two molecules of pyruvic acid, a 3-carbon compound. Glycolysis takes place in the cytoplasm of a cell. Through glycolysis, the cell gains 2ATP molecules. In addition, the electron carrier NAD~ accepts a pair of high-energy electrons, producing NADH. By doing this, NAD~ helps passenergy from glucose to other pathways in the cell. When oxygen is not present, fermentation follows glycolysis. Fermentation releases energy from food molecules by forming ATE Fermentation does not need oxygen, so it is said to be anaerobic. During fermentation, cells convert NADH back into the electron carrier NAD~ that is needed for glycolysis. This lets glycolysis continue to make a steady supply of ATP. The two types of fermentation are alcoholic fermentation and lactic acid fermentation. Yeasts and a few other microorganisms carry out alcoholic fermentation. The equation for alcoholic fermentation after glycolysis is: pyruvic acid + NADH ~ alcohol + CO2 + NAD~ Lactic acid fermentation occurs inmuscles during rapid exercise. The equation for lactic acid fermentation after glycolysis is: pyruvic acid + NADH ~ lactic acid + NAD~ If oxygen is present, the Krebs cycle and electron transport chain follow glycolysis. Together, these pathways make up cellular respiration. Cellular respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen. Cellular respiration takes place in niltochondria. The equation for cellular respiration is: 6O~ + C6H C02 + H2O + Energy oxygen + glucose carbon dioxide + water + Energy Pearson Educafion, Inc., publishing as Pearson Prenhce Hall. 82

2 Name Class Date 9-2 The Krebs Cyde and flectron Transport Cellular respiration requires oxygen, soit is said to be aerobic. The Krebs cycle is the second stage ofidellular respiration. During the Krebs cycle, pyruvicacid is broken down into carbon dioxide in a series of energy-extracting reactions. The Krebs cycle is also known as the citric acid cycle, because citric acid is one of its first products. Here are the stages of the Krebs cycle. The Krebs cycle starts when pyruvic acid formed by glycolysis enters the mitochondrion. The pyruvic acid is broken down iflto carbon dioxide and a 2-carbon acetyl group. The two carbons of the acetyl group join a 4-carbon com- 4 pound to produáe citric acid. The Kr.ebs ~cle continues in a series of reactions~ In these reactions, two energy carriers accept high-energy electrons. NAD~ is changed to NADH, and FAD is changed to FADH2. These molecules carry the high-energy electrons to the electron trañspôtt chain. The carbon dioxide is released as a waste product. The electron transport chain uses the high-energy electrons to change ADPinto ATP. Tn the electron transport chain, highenergy elçctrons move from one carrier protein to the next. At ) the end of the chain,, oxygen pulls electrons from the final carrier molecule. These~ electrons join with hydrogen ions, forming water. Each transfer along the chain releases a small amount of energy ATP synthase uses..the energy to produce ATE Glycolysis produces 2 ATP molecules from one molecule of glucose The Krebs cycle and the electron transport chain let the cell form 34 ATP moleculeá ~er glucose molecule. The total, then, for cellular respiration is36 ATP molecules per glucose molecule The energy flows in photosynthesis and cellular respiration occur in opposite directions On a global level, photosynthesis and cellular respiration are also opposites Photosynthesis removes carbon dioxide from the atmosphere and puts back oxygen Cellular respiration removes oxygen from the atmosphere and puts back carbon dioxide I S. Pearson Education, nc, publishing as Pearson Prentice Hall 83

3 IF flu II U Ii I II III Fiji II Name Class Date The M~tochondr~on In plant and animal cells, the final stages of cellular respiration take place in mitochondria. A mitochondrion has two membranes. The inner membrane is folded up inside the outer membrane. The space between the inner and outer membranes is called the intermembrane space. The space inside the inner membrane is called the matrix. Label the inner membrane, intermembrane space, matrix, and outer membrane~ i~if J ri F) I, Answer the questions. Circle the correct answer. 1. In which membrane is the electron transport chain located? outer membrane iiuier membrane Pearson Educofion, Inc., publishing as Pearson Prenfice Hall. nil

4 ..~ Name. cins_ Date CeUubr Respfrat~on Overview Cellular respiration is the process that rejeases energy from food -in the presence of oxygen. Glucose Use the words below to label the diagram of cellular respiration on the lines provided ATP. glycolysis niitochondrion electron transport chain Krebs cycle Use the diagram to answer the questions. 1. Where does glycolysis take place? 2. Where do the Kreb cycle and electron transport chain take place? Peorsan Educohon, Inc., publishing us PeQrson Prenlice Null. 85

5 Name Class Date 0 Ce~hsDar ~espfrat~o~i and Photosynthesis Cellular respiration and photosynthesis can be thought of as opposite processes. Energy flows in opposite directions in the two processes. Complete the table using the words below. Some cells have been completedfor you. Some words may. be used more than once. carbon dioxide energy release mitochondria water Photosynthesis Cellular Respiration Function energy capture Location chioroplasts 0 Reactants glucose; oxygen Products oxygen; glucose Use the table to answer the quçstions. 1. Which process releases energy for the cell? Circle th? correct answer. cellular respiration photosynthesis 2. For which reaction is 6C02 + 6H20. C6H O~ the correct equation? Circle the correct answer. cellular respiration photosynthesis 3. How do the products of phobsynthesis compare to the reactants of cellular respiration? Pearson EdpCOIIOA, Inc., publishing as Pearson Prenhce Hall. 89

9-1 Chemical Pathways

9-1 Chemical Pathways 2 of 39 Food serves as a source of raw materials for the cells in the body and as a source of energy. Animal Cells Animal Mitochondrion Plant Plant Cells 3 of 39 1 Both plant and animal cells carry out