Cellular Respiration - Cellular Respiration Catabolic...

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Cellular Respiration Catabolic Pathways Yield Energy by Oxidizing Organic Fuels Catabolic pathways – Metabolic pathways that release stored energy by breaking down complex molecules **Catabolic Pathways and Production of ATP Organic compounds have potential energy b/c of the arrangement of their atoms Compounds in exergonic reactions can act as fuels A cell degrades complex organic molecules with lots of potential energy into simpler waste products w/ low PE - Some energy taken out can be used to do work, other is lost as heat Fermentation – A partial degradation of sugars that occurs without the use of O2 Aerobic Respiration – Oxygen is consumed as a reactant along with the organic fuel - Most prevalent & efficient catabolic pathway - Used by eukaryotes and prokaryotes Anaerobic Respiration – Harvesting chemical energy without using any O2 - Used by prokaryotes Overall process of aerobic respiration: Organic compounds + O2 CO2 + H2O + Energy Degradation of Glucose: C6H12O6 + 6O2 6CO2 + 6H2O + energy(ATP + Heat) Glucose is the fuel cells most often use - Breakdown of glucose is exergonic (free energy = -686 kmal/mol) *Note: negative free energy = spontaneous reaction The relocation of electrons releases energy stored in organic molecules [used to synthesize ATP] Redox reactions – Transfer of one or more electrons from one reactant to the other - Oxidation: loss of electrons from one substance - Reduction: Adding electrons to another substance - Reducing Agent: Electron donor [gets oxidized] - Oxidizing Agent: Electron acceptor [gets reduced] *Note: B/c oxygen is so electronegative, it’s one of the strongest oxidizing agents A redox reaction that moves electrons closer to oxygen [releases chemical energy that can be put to work] Respiration: oxidation of glucose and other molecules in food The energy state of the electron changes as hydrogen (& its electron) is transferred to oxygen - The oxidation of glucose transfers electrons to a lower energy state [energy released ATP] Carbs & fats have lots of electrons & hydrogens but an activation energy holds the back the electrons to a lower energy state - Activation energy supplied by igniting glucose [686 kcal of heat/mol) *B/c body temperature isn’t high enough, enzymes lower the activation energy allowing glucose to be oxidized Cellular respiration doesn’t oxidize glucose in a single step - Broken down in a series of steps - Electrons (paired with protons) are stripped from glucose The hydrogen atoms are not transferred directly to oxygen but are first passed to an electron carrier (NAD+, a coenzyme) - NAD+ functions as a n oxidizing agent during respiration - Works via dehydrogenases (remove a pair of H atoms [2 electrons, 2 protons] from the substrate,
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oxidizing it) - NAD+ becomes NADH + H+ Each NADH molecule formed during respiration represents stored energy that can be used to
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This note was uploaded on 09/17/2009 for the course BIO G 101 taught by Professor Gilbert,c. during the Fall '07 term at Cornell University (Engineering School).

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Cellular Respiration - Cellular Respiration Catabolic...

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