CELLULAR RESPIRATION Teacher's Guide Cellular Respiration Teacher's Guide This teacher's guide is designed for use with the CellularRespiration series of programs produced by TVOntario, the television service of the On- tario Educational Communications Authority. The series is available on videotape to educational institutions and nonprofit organizations. The Series Producer/Director . David Chamberlain Project Officers. John Amadio, David Way Writers: Susan Perry, David Way Consultant. Robert Whitney The Guide Writers: Randee Crisp, George Laundry, Robert Whitney Graphic Designer: Roswita Busskamp Copyright 1990 by The Ontario Educational Communications Authority. All rijahts reserved. Printed in Canada. 3626/90 Introduction 1 1. The Cell and Energy 3 2. Glycolysis 1 6 3. Glycolysis 2 9 4. The Krebs Cycle 12 5. Oxidative Phosphorylation 14 6. Metabolism and Nutrition 17 Glossary 19 Bibliography 21 This series of six 10-minute programs illustrates • discuss glucose as the principal fuel of cellular the complex world of biological respiration, at respiration and the involvement of ATP as the. both macro and molecular levels. Beginning with energy shuttle; a historical perspective and progressing to mod- ern research and theories, the programs examine • develop, in step-by-step fashion, the metabo- enzymes and coenzymes, phosphorylation, bio- lism of glucose through the processes of synthesis, glycolysis, and the Krebs cycle. glycolysis, the Krebs or citric acid cycle, and oxidative phosphorylation; Together, the Cellular Respiration video series and teacher's guide: • elucidate the role of oxygen in the controlled combustion of glucose with the concomitant • describe the evolution of cellular respiration production of the respiratory waste product that presaged the development of present- carbon dioxide; and day life forms; • explain the relationships of the three food • investigate the structure and function of the groups-proteins, fats, and carbohydrates- mitochondrion organelle as the prime locus in nutrition. for the biosynthesis of adenosine triphosphate (ATP); 1 After viewing this program and completing the Regardless of its source, energy for living things suggested activities, students should be able to: must be readily available at all times. Since inputs are irregular and unreliable, constant availability • name three major classes of molecules that necessitates some form of energy storage. A brief living things use to store energy, and designate overview of the mechanism of energy storage and carbohydrates as those most frequently em- release is the subject of this introductory program. ployed; The digestive system extracts from an animal's food • explain the meanings of the following terms: the three major groups of macromolecules: pro- cytosol, mitochondrion, matrix, cristae, adeno- teins, fats, and carbohydrates.The most immedi- sine triphosphate (ATP), high-energy bond, ately available energy has been stored in carbohy- phosphoryl group, adenosine diphosphate drates. This series assumes that most energy is (ADP), phosphorylation; provided to the cell in the form of glucose mole- cules. The release of chemical energy, to a form • describe the appearance of a mitochondrion as useful to living things, is called cellular respiration. seen through the transmission electron micro- scope; Cellular respiration is a complex series of chemical reactions that occur in both the cytosol and the • account for the theory that both mitochondria mitochondria of a cell. A mitochondrion consists of and chloroplasts evolved from independent a pair of membranes surrounding an amorphous organisms; interior, the matrix. The innermost membrane forms many inward-facing folds, the cristae, which • describe the structure of an ATP molecule and greatly increase the amount of membrane that can locate, within this structure, high-energy bonds; be packed within the mitochondrion. The similar- ity of a mitochondrion to a tiny cell suggests that the • explain the role of ATP in cell metabolism; mitochondria, like the chloroplasts, may have evolved from independent beings that invaded • name three interconnected phases of cellular larger cells as parasites. Over millions of years, they respiration. Crista 3 became tolerated by, then vital to, their hosts. As a The reactions of cellular respiration, which provide consequence, there are many similarities between the ATP needed to drive life processes, are subdi- cellular respiration and photosynthesis. In fact, in vided into three phases: glycolysis, the Krebs cycle, many ways, cellular respiration can be considered and oxidative pbospborylation. All three phases the reverse of photosynthesis. will be covered, in turn, by this series. Cellular respiration transfers most of the glucose molecules' energy into smaller "packages" of po- BEFORE VIEWING tential energy in molecules of adenosine triphosphate (ATP). ATP molecules contain enough energy to drive typical metabolic reactions. Some students may have little exposure to chem- istry. A short lesson on (or review of) the concepts of element, compound, atom, molecule, and cova- ATP is a complicated molecule consisting of por- lent bond should precede the program. Emphasize tions of a number of simpler, and more familiar, that a detailed knowledge of the structures of molecules linked by covalent bonds. The simple respiratory intermediates is not necessary. Instead, "building blocks" are a nitrogen-containing base the student should appreciate that molecules have (adenine), a five-carbon sugar (ribose), and three unique and predictable shapes, and that cells molecules of phosphoric acid. The energy resides possess specialized agents (enzymes) that are able at one of two higb-energy bonds between the remanants of phosphoric acid molecules to select one type of molecule from among the (phosphoryl groups). When an ATP molecule multitude of other molecules present in the cell. A provides energy to a reactant, it transfers one of its quick review of a typical food chain and the place "high-energy bonds" to the reactant. Of course, of autotrophs and heterotrophs within it could also some atoms of the ATP are also transferred. be useful. Typically, the end phosphoryl group is transferred to the reactant, and adenosine dipbospbate (ADP) is left over. The reactant is now said to be AFTER VIEWING "phosphorylated" and the process of transferring a phosphoryl group to the reactant is called Activity l: phospborylation. Phosphorylation reactions are often employed in metabolism as a step in an How Carbohydrates Got Their energy-consuming reaction. Name Apparatus sugar cubes concentrated sulphuric acid (Caution: highly corrosive) crucible mortar and pestle protective cover for desktop safety goggles laboratory coat or apron Note: This activity maybe performed as a demonstration. Method 1. Grind a sugar cube to a powder using a mortar and pestle. 2. Transfer the powdered sugar to a crucible which has been placed on a protective cover to prevent FIGURE 1.1 Structure of ATP damage to the desktop. 4 3, Be sure you are wearing safety goggles. Add hydroxyl groups (-OH) are in the correct just enough concentrated sulphuric acid to the positions above or below the ring. Use as few crucible to cover the sugar. shifts of atoms and/or bonds as possible. In 4. Note the color, odor, and appearance of the your notes, record the steps you followed in material left in the crucible. What do you think this conversion. Also record the number of it is? times you had to rotate a part of the molecule without shifting bonds or atoms. Compare Discussion your results with those of other students in the Concentrated sulphuric acid is a powerful dehy- class. Have your model evaluated by your drating agent which will withdraw water from instructor before proceeding. Be sure to make other compounds, Assume that this will happen in any alterations suggested by the instructor this experiment. In terms of elements, what ap- before continuing. pears to be the composition of the sugar, based on the color of the resultant residue? Why, then, are 5. Evaluate the flexibility of the model. Is the this and other sugars referred to as "carbohy- positioning of a hydroxyl group (-OH) on the drates"? top or bottom of the formula significant? Comment in your notes. Activity 2: Discussion Visualizing Molecules 1. The formula of glucose is given in textbooks as C6H1z06. To which of the structures in Figure 1.2 does it apply? Research the meaning of Apparatus isomer and isomerization and explain how molecular model kit these terms relate to this activity. Method 2. Cellobiose is a disaccharide formed during the 1. Examine the contents of the molecular model digestion of cellulose, and maltose is a disac- kit. Note that there are wood spheres of vari- charide formed during the digestion of starch. ous colors. These represent atoms of the Research the structures of these two sugars and elements. You will be using only carbon (black), relate them to this activity. Can enzymes distin- hydrogen (white), and oxygen (red) in this guish between these two disaccharides? exercise. 2. Construct a model of a glucose molecule. Use the structural formula on the left of Figure 1.2 for guidance. When the model has been completed to your satisfaction, take it to your i nstructor for evaluation. Make any alterations suggested by your instructor before you con- tinue. 3. Evaluate the flexibility of the model. Is the positioning of a hydroxyl group (-OH) on the right or left of the formula significant? Com- ment in your notes.