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Unformatted text preview: P a g e | P a g e | [ CAMPBELL BIOLOGY: CHAPTER 9 NOTES ] Chapter 9 – Cellular Respiration: Ha rvesting Chemical Energy Overview: Life Is Work • To perform their many tasks, living cells require energy from outside sources. • Energy enters most ecosystems as sunlight and leaves as heat. • Photosynthesis generates oxygen and organic molecules that the mitochondria of eukaryotes use as fuel for cellular respiration. • Cells harvest the chemical energy stored in organic molecules and use it to regenerate ATP, the molecule that drives most cellular work. • Respiration has three key pathways: glycolysis, the citric acid cycle, and oxidative phosphorylation. Concept 9.1 Catabolic pathways yield energy by oxidizing organic fuels • The arrangement of atoms of organic molecules represents potential energy. • Enzymes catalyze the systematic degradation of organic molecules that are rich in energy to simpler waste products with less energy. • Some of the released energy is used to do work; the rest is dissipated as heat. • Catabolic metabolic pathways release the energy stored in complex organic molecules. • One type of catabolic process, fermentation, leads to the partial degradation of sugars in the absence of oxygen. • A more efficient and widespread catabolic process, cellular respiration, consumes oxygen as a reactant to complete the breakdown of a variety of organic molecules. ° In eukaryotic cells, mitochondria are the site of most of the processes of cellular respiration. • Cellular respiration is similar in broad principle to the combustion of gasoline in an automobile engine after oxygen is mixed with hydrocarbon fuel. ° Food is the fuel for respiration. The exhaust is carbon dioxide and water. • The overall process is: ° organic compounds + O 2 CO 2 + H 2 O + energy (ATP + heat). • Carbohydrates, fats, and proteins can all be used as the fuel, but it is most useful to consider glucose. ° C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + Energy (ATP + heat) • The catabolism of glucose is exergonic with a ∆ G of 686 kcal per mole of glucose. − ° Some of this energy is used to produce ATP, which can perform cellular work. Redox reactions release energy when electrons move closer to electronegative atoms. • Catabolic pathways transfer the electrons stored in food molecules, releasing energy that is used to synthesize ATP. • Reactions that result in the transfer of one or more electrons from one reactant to another are oxidation-reduction reactions, or redox reactions. ° The loss of electrons is called oxidation. ° The addit ion of elect rons is called reduction. • The formation of table salt from sodium and chloride is a redox reaction....
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This note was uploaded on 07/24/2008 for the course BIO 120 taught by Professor Staff during the Fall '07 term at USC.
- Fall '07
- Cellular Respiration