ch9 - Chapter 9: Cellular Respiration: Harvesting Chemical...

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Biology 2107 Chapter 9: Cellular Respiration : Harvesting Chemical Energy 1 Chapter 9: Cellular Respiration : Harvesting Chemical Energy Metabolism . Two types: 1. Anabolism: Condensation or dehydration. Energy required. 2. Catabolism: Hydrolysis. Breaking down complex organic ,molecules to simpler ones. Energy is released. Com.Org.Mol(rich in E)------- Æ Simpl.Org.Mol (Poor in E) Two types: a. Fermentation: Partial degradation of sugar. Some energy is released and there is no O2 involved. b. Cellular respiration: Complete degradation of sugar and some other organic molecules. More energy is released. And O2 is required. Analogy: Gasoline combustion in cars and cellular respiration. C a r C e l l F u e l F o o d O 2 O 2 H2O + CO2 Exhaust In cell: Organic molecules + O2---- Æ CO2 + H2O + energy carbohydrates, fats, proteins We will study : C6H12O6 + O2 - Æ Co2 + H2o + energy Co2 + H2O < C6H12O6 This is an exergonic reaction Where ATP is being used up in the cell? For various functions and cell activities. A-P-P-P ------------- Æ A-P-P + Pi + energy ( Hydrolysis of ATP) A-P-P + Pi + energy------- Æ A-P-P-P In living cell this cycle goes on and on. A working muscle cell converts 10 millions ATP per second. Where this energy to convert ADP to ATP come from? From catabolism of organic molecules (sugar) by the process of Oxidation/reduction. Glucose is completely oxidized to CO2, H2O, and releases energy. What is oxidation? Loss of one or more electron(s) What is reduction? Gain of one or more electron(s) In glucose catabolism, electrons are removed from sugar in a stepwise fashion.
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Biology 2107 Chapter 9: Cellular Respiration : Harvesting Chemical Energy 2 Always a substance should be oxidized and another one be reduced (coupled). This is called REDOX (Reduction and oxidation). Example of REDOX: Na + Cl- ---------------------- Æ Na + + Cl - Na has lost en electron: it is oxidized Cl has gained en electron: It is reduced Xe - + Y ---------------- Æ X + Ye - X= is an electron donor - Æ also called a reducing agent Y= is an electron acceptor- Æ also called oxidizing agent Not always we have complete transfer of electrons: CH4 + 2O2 ------------------ Æ CO2 + 2H2O + E CH4 -- Æ oxidized to CO2 O2 ---- Æ reduced to H2O In this case, there is no electron transfer. Some molecules change degree of electron sharing in covalent bonds which releases energy. Electrons are falling to Oxygen and as a result they loose their potential energy. In Cellular respiration, electrons move(fall) from sugar to oxygen and as a result, energy is released: this energy is being used up to convert ADP to ATP. These electrons are removed along with Hydrogen. So, in general, molecules rich in hydrogen (hydrocarbons) are more energetic. So, what liberates energy in cellular respiration? Change in covalent status of
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This note was uploaded on 11/29/2010 for the course BUSSINESS 221242 taught by Professor Michaeldouglas during the Spring '10 term at Georgia Perimeter.

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ch9 - Chapter 9: Cellular Respiration: Harvesting Chemical...

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