Lecture 20, 21, 22 - Ch 9

Lecture 20, 21, 22 - Ch 9 - Chapter 9 Cellular Respiration...

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Chapter 9 – Cellular Respiration Overview Photosynthesis generates oxygen and organic molecules used by the mitochondria of eukaryotes as fuel for cellular respiration. Respiration breaks this fuel down, generating ATP. The waste products of this type of respiration, CO2 and water, are the raw materials for photosynthesis. In this chapter, we consider how cell harvest the chemical energy stored in organic molecules and use it to generate ATP, the molecule that drives most cellular work. 9.1 Catabolic pathways yield energy by oxidizing organic levels Catabolic Pathways and Production of ATP Catabolic pathways release stored energy by breaking down complex molecules. Electron transfer plays a major role in these pathways. With the help of enzymes, a cell systematically degrades complex organic molecules that are rich in potential energy to simpler waste products that have less energy. Some of the energy taken out of chemical storage can be used to do work; the rest is dissipated as heat. Fermentation , is a partial degradation of sugars that occurs without the use of oxygen. However, the most prevalent and efficient catabolic pathway is aerobic respiration , in which oxygen is consumed as a reactant along with the organic fuel. The cells of most eukaryotic and prokaryotic organisms carry this type of respiration out. Some prokaryotes use substances other than oxygen as reactants in a similar process that harvests chemical energy without using any oxygen at all in a process called anaerobic respiration . Cellular respiration is often used to refer to the aerobic process. It is helpful to learn the steps of cellular respiration by tracking the degradation of the sugar glucose: - C6H12O6 + 6O2 à 6CO2 + 6H2O + en ergy (ATP + h e at) The breakdown of glucose is exergonic. A –ΔG m e a ns that the products of the che mical process store less en ergy than the reactants and that the reaction can happ en spontan eously (witho input of e n ergy) Redox Reactions: Oxidation and Reduction The Principle of Redox Redox reactions is where there are a transfer of one or more electrons ( e- ) from one reactant to another. In a redox reaction, the loss of electrons from one substance is called oxidation , and the addition of electrons to another substance is known as reduction ( Adding electrons is called reduction ; negatively charged electrons added to an atom reduce the amount of positive charge of that atom.) Consider the reaction between Na and Cl that forms table salt: We could generalize a redox reaction this way: X e- , the electron donor, is the reducing agent ; it reduces Y, which accepts the donated electron. Y, the electron acceptor, is the oxidizing agent
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Lecture 20, 21, 22 - Ch 9 - Chapter 9 Cellular Respiration...

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