Lecture 8 Fermentation andCellularRespiration

Lecture 8 Fermentation andCellularRespiration -...

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1 Cellular Respiration: Harvesting Chemical Energy Thermodynamics in the Real World Energy flows into an ecosystem as sunlight and leaves as heat Light energy ECOSYSTEM CO 2 + H 2 O Photosynthesis in chloroplasts Cellular respiration in mitochondria Organic molecules + O 2 ATP powers most cel ular work Heat energy Figure 9.2 ATP synthesis from ADP + P i requires energy ATP ADP + P i Energy for cel ular work (endergonic, energy- consuming processes) Energy from catabolism (exergonic, energy yielding processes) ATP hydrolysis to ADP + P i yields energy Figure 8.12 Catabolic Pathways Anabolic Pathways To keep working Cells must regenerate ATP Catabolic Pathways Produce ATP The breakdown of organic molecules is exergonic
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2 Cellular Respiration Is a catabolic pathway that yields energy by oxidizing organic fuel to produce energy in the form of ATP Organic Fuel + O 2 CO 2 + H 2 O + Energy Fats, Carbohydrates, Protein Cellular respiration -Is the most prevalent and efficient catabolic pathway -Consumes oxygen and organic molecules such as glucose -Yields ATP Example--glucose C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + Energy (Fuel) (Stored as ATP) Redox Reactions: Oxidation and Reduction Catabolic pathways yield energy Due to the transfer of electrons Redox reactions Transfer electrons from one reactant to another by oxidation and reduction XH + Y X + YH In oxidation A substance loses electrons, or is oxidized In reduction A substance gains electrons, or is reduced XH + Y X + YH becomes oxidized (loses electron) becomes reduced (gains electron)
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3 Examples of redox reactions Na + Cl Na + + Cl becomes oxidized (loses electron) becomes reduced (gains electron) Some redox reactions Do not completely exchange electrons Change the degree of electron sharing in covalent bonds CH 4 H C OO O O O C Methane (reducing agent) Oxygen (oxidizing agent) Carbon dioxide Water + 2O 2 CO 2 + Energy + 2 H 2 O becomes oxidized becomes reduced Reactants Products Figure 9.3 Oxidation of Organic Fuel Molecules During Cellular Respiration During cellular respiration Glucose is oxidized and oxygen is reduced C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + Energy becomes oxidized becomes reduced O 2 is the “oxidizing agent” (becomes reduced) Glucose is the reducing agent (becomes oxidized) -Cellular respiration oxidizes glucose in a series of steps -Electrons stripped from glucose are not directly transferred to O 2 C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + Energy becomes oxidized becomes reduced
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4 Electrons from organic compounds Are first transferred to a Coenzyme Carrier NAD+: niacin= nicotinamide adenine dinuleotide NAD + + 2H Æ NADH + H + FAD: riboflavin= flavin adenine dinucleotide FAD + 2H Æ FADH 2 The H (electrons) come from the oxidation of glucose Loses 2 electrons (oxidized) gains 2 electrons (reduced) NAD + H O O OO O O O O O O P P CH 2 CH 2 HO OH H H HO OH HO H H N + C NH 2 H N H NH 2 N N Nicotinamide (oxidized form) NH 2 + 2[H] (from food) Dehydrogenase Reduction of NAD + Oxidation of NADH 2 e + 2 H + 2 e + H + NADH O H H N C + Nicotinamide
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Lecture 8 Fermentation andCellularRespiration -...

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