09_Cellular Respiration and Fermentation.doc

09_Cellular Respiration and Fermentation.doc - LEARNING...

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LEARNING OBJECTIVES: CHAPTER 9 CELLULAR RESPIRATION AND FERMENTATION This chapter very nicely demonstrates the fundamental characteristic of life, ENERGY! To stay alive and reproduce, organisms have to acquire and use energy. This chapter is also an extension of Ch. 8: Energy and Enzymes: An Introduction to Metabolic Pathways You should recognize many of those principles and concepts in Cellular Respiration and Fermentation! In this section, there is a tendency to get caught up in tiny details; don’t forget to see the forest through the trees! (i.e., always keep the “big picture” in mind). C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + ATP An Overview of Cellular Respiration (Concept 9.1): 1. Describe the purpose of cellular respiration and its importance for organisms. Cellular respiration is the process by which cells in plants and animals break down sugar and turn it into energy, which is then used to perform work at the cellular level. The purpose of cellular respiration is simple: it provides cells with the energy they need to function. 2. Recall from Ch. 8 that redox reactions are a form of energy transfer. In a redox reaction, explain why the reduced molecule GAINS energy and the oxidized molecule LOSES energy . Oxidation occurs when a molecule loses an electron or increases its oxidation state. When a molecule is oxidized, it loses energy. In contrast, when a molecule is reduced, it gains one or more electrons. As you might have guessed, the molecule gains energy in the process. 3. Explain how glucose is oxidized and why this is a long series of redox reactions instead of a quick burn. Glucose is oxidized by the cell splitting into two molecules of pyruvate, which takes a series of 10 reactions which are collectively called glycolysis. The remainder of glucose oxidation is the Krebs Cycle. This takes a long time for the electrons to be pulled apart from the covalent bonds. 4. Glucose oxidation is a four-step process. What are these steps and what are the major events associated with each? In glycolysis, glucose undergoes a series of chemical transformations. In the end, it gets converted into two molecules of pyruvate. Each pyruvate from glycolysis goes into the mitochondrial matrix. There, it’s converted into a two-carbon molecule bound to Coenzyme A. In the citric acid cycle, the acetyl CoA made in the last step combines with a four-carbon molecule and goes through a cycle of reactions, ultimately regenerating the four-carbon starting molecule. In oxidative phosphorylation everything made in other steps deposit their electrons in the electron transport chain, turning back into their "empty" form. As electrons move down the chain, energy is released and used to pump protons out of the matrix, forming a gradient.
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