bio- chap 9 - I. Principles of Energy Harvest A. Obtaining...

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I. Principles of Energy Harvest A. Obtaining Energy 1. Organic comps store EG int ehry arrangement of atoms. W/ enzymes, cells systematically degrade complex organic molecules thaat have high potential EG to simpler waster products w/ less EG 2. Energy harvested is used to do work. Rest is dissipated as heat 3. Catabolic pathways: metabolic pathways that release stored EG by breaking down comples molecules a. fermentation: partial degradation of sugars that occurs without the help of O 2 b. Cellular Respiration (CR) - most prevalent and efficient catabolic pathway - O 2 consumed along w/ organic fuel - Mitochondria - Organic Compounds + O 2 -> CO 2 + Water + Energy - C 6 H 12 O 6 + 6O 2 -> 6CO 2 + 6H 2 O + Energy (ATP+Heat) degradation of sugar glucose exergonic, free energy change of –686 kcal per mole of glucose (-∆G means products of chem process store less EG than the reactants) B. ATP (adenosine triphosphate) 1. close packing of three negatively charged phosphate groups make it unstable, and an EG storing arrangement b/c charges repel each other 2. cell uses Eg source by using enzymes to transfer phosphate groups from ATP to other comps, which are phosphorylated 3. when molecule loses third terminal tri-phosphate, it ‘relaxes’ 4. ATP -> ADP and an ingoranic phosphate(Pi), which store less EG than ATP C. Redox reactions 1. relocation of electrons releases EG stored in food molecules, and this EG is used to synthesize ATP 2. subs losing electrons undergoes oxidation but is the reducing agent 3. subs lgaining electrons undergoes reduction but is the oxidizing agent 4. relocated electrons closer to oxygen D. Electrons “fall” from organic molecules to oxygen during CR 1. organic molecules have an abundance of hydrogen, so electrons fall to lower energy oxygen bonds 2. CR oxidation of glucose takes EG out of sotrage and makes it available for ATP synthesis 3. Glucose would combine spontaneously with oxygen b/c its rich in hydrogen and electrons associated with it E. role of NAD+ in CR 1. gradual series of steps in CR that strip hydrogen from glucose, but are not transferred directly to oxygen 2. hydrogen atoms passed to coenzyme NAD+, which functions as an oxidizing agent during respiration
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3. dehydrogenases remove a pair of hydrogen atoms from the substrate so NAD+ can trap electrons from glucose 4. 5.
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This note was uploaded on 02/25/2012 for the course BIO 1421 taught by Professor Farr during the Fall '08 term at Texas State.

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bio- chap 9 - I. Principles of Energy Harvest A. Obtaining...

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