Chapter 9 - Cellular Respiration - Harvesting Chemical Energy

Chapter 9 - Cellular Respiration - Harvesting Chemical Energy

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Chapter 9 Class Notes – Cellular Respiration – Page 1 Max Sauberman AP Biology – Mr. Schilp Chapter 9 Cellular Respiration: Harvesting Chemical Energy Life is Work: Living cells require energy from outside sources. Some animals obtain energy by eating plants; others feed on organisms that eat plants. Energy flows into an ecosystem as sunlight and leaves as heat. Dual Energy Processes: Photosynthesis generates oxygen and organic molecules, used in cellular respiration. Cells use chemical energy stored in organic molecules to regenerate ATP. The products of photosynthesis (organic molecules and oxygen) are the reactants for cellular respiration, which produces the reactants for photosynthesis (carbon dioxide and water). The Structure and Hydrolysis of ATP: Adenosine triphosphate is the cell’s energy shuttle, and provides energy for cellular functions. ATP is made of the adenine nitrogenous base, ribose sugar, and three phosphate groups. Between the phosphate groups are high-energy bonds, and the bonds can be broken by hydrolysis. When the bonds break (especially the terminal phosphate bond), a lot of energy is released. The release of energy comes from the chemical change to a state of lower free energy. The hydrolysis of ATP is: ATP (P) i + ADP (adenosine diphosphate) + energy Coupled Exergonic and Endergonic Reactions: In the cell, the energy from the exergonic reaction of ATP hydrolysis can be used to drive an endergonic reaction. The coupled reactions are overall exergonic (-ΔG) and are spontaneous reactions. How ATP Performs Work: ATP drives endergonic reactions by phosphorylation, transferring a phosphate group to a reactant molecule. The recipient molecule is now known to be phosphorylated. The three types of cellular work (mechanical, transport, chemical) are all powered by ATP hydrolysis.
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Chapter 9 Class Notes – Cellular Respiration – Page 2 Catabolic Pathways: Catabolic pathways yield energy by oxidizing organic fuels. Several processes are central to cellular respiration and related pathways. The catabolic breakdown of organic molecules (in cellular respiration) is exergonic. Fermentation vs. Respiration: Fermentation is a partial degradation of sugars that occurs without the presence of O 2 . Cellular respiration consumes oxygen and organic molecules (starting with the sugar glucose) and yields ATP. Redox Reactions – Oxidation and Reduction: The transfer of electrons during chemical reactions releases energy stored in organic molecules. This released energy is ultimately used to synthesize ATP. Chemical reactions that transfer electrons between reactants are called oxidation-reduction (redox) reactions. In oxidation, a substance loses electrons, and is oxidized. In reduction, a substance gains electrons, and is reduced. (Positive charge is reduced)
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This note was uploaded on 03/17/2011 for the course BIO 101 taught by Professor Sullivan during the Spring '08 term at Harvard.

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Chapter 9 - Cellular Respiration - Harvesting Chemical Energy

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