chpater 8 - Biol 113 AU2010 Lecture 8 Cellular...

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1 Biol 113 AU2010 Lecture 8 Cellular Respiration (I) A. An overview of energy flow B. Catabolic pathways yield energy by oxidizing organic fuels C. Three stages of cellular respiration D. Glycolysis harvests chemical energy by oxidizing glucose to pyruvate E. The citric acid cycle completes the energy-yielding oxidation of organic molecules Fig. 9.2 Light energy ECOSYSTEM Photosynthesis in chloroplasts CO 2 + H 2 O Cellular respiration in mitochondria Organic molecules + O 2 ATP powers most cellular work Heat energy ATP Energy flows into an ecosystem as sunlight and leaves as heat Photosynthesis generates O 2 and organic molecules, which are used in cellular respiration Cells use chemical energy stored in organic molecules to regenerate ATP, which powers work A. An Overview of Energy Flow
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2 B. Catabolic Pathways Yield Energy by Oxidizing Organic Fuels Several processes are central to cellular respiration and related pathways The breakdown of organic molecules is exergonic Fermentation is a partial degradation of sugars that occurs without O 2 Aerobic respiration consumes organic molecules and O 2 and yields ATP Anaerobic respiration is similar to aerobic respiration but consumes compounds other than O 2 Cellular respiration includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration Although carbohydrates, fats, and proteins are all consumed as fuel, it is helpful to trace cellular respiration with the sugar glucose: C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + Energy (ATP + heat) The transfer of electrons during chemical reactions releases energy stored in organic molecules This released energy is ultimately used to synthesize ATP The Principle of Redox Chemical reactions that transfer electrons between reactants are called oxidation- reduction reactions, or redox reactions In oxidation , a substance loses electrons, or is oxidized In reduction , a substance gains electrons, or is reduced (the amount of positive charge is reduced) becomes oxidized (loses electron) becomes reduced (gains electron) becomes oxidized becomes reduced Fig. 9-UN1 Fig. 9-UN2
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3 The electron donor is called the reducing agent The electron receptor is called the
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