ch 7 lecture - Chapter 7: Harvesting the fixed energy of...

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Chapter 7: Harvesting the fixed energy of photosynthesis to produce cellular energy
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2 Respiration Organisms can be classified based on how they obtain energy: Autotrophs Able to produce their own organic molecules through photosynthesis Heterotrophs Live on organic compounds produced by other organisms All organisms use cellular respiration to extract energy from organic molecules
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3 Cellular respiration Cellular respiration is a series of reactions Oxidations – loss of electrons Dehydrogenations – lost electrons are accompanied by protons A hydrogen atom is lost (1 electron, 1 proton)
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4 Redox During redox reactions, electrons carry energy from one molecule to another Nicotinamide adenosine dinucleotide (NAD +) is an example An electron carrier NAD + accepts 2 electrons and 1 proton to become NADH Reaction is reversible
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5 Fig. 7.1 – Redox rxs often employ cofactors
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In overall cellular energy harvest Dozens of redox reactions take place Number of electron acceptors including NAD + In the end, high-energy electrons from initial chemical bonds lose their energy through ETS and these electrons are then transferred to a final electron acceptor – bottom line/take home message!!!! 6 Overall Picture of Cellular Respiration:
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7 Aerobic respiration – Final electron receptor is oxygen (O 2 ) Anaerobic respiration Final electron acceptor is an inorganic molecule (not O 2 ) Fermentation Final electron acceptor is an organic molecule Types of Respiration
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8 Aerobic respiration C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O G = -686kcal/mol of glucose G can be even higher than this in a cell This large amount of energy must be released in small steps rather than all at once. Otherwise, what would happen?
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9 Fig. 7.2 – How and Electron Transport System works
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Electron carriers in an ETS Many types of carriers used Soluble, membrane-bound, move within membrane All carriers can be easily oxidized and reduced Some carry just electrons, some electrons and protons NAD+ acquires 2 electrons and a proton to become NADH– note difference of NADPH 10
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11 Fig. 7.3 NAD + and NADH
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12 ATP Cells use ATP to drive endergonic rxs. ΔG = -7.3 kcal/mol 2 mechanisms for synthesis **** 1.Substrate-level phosphorylation Transfer phosphate group directly to ADP During glycolysis 1.Oxidative phosphorylation ATP synthase uses energy from a proton gradient Re-review Fig. 8.15
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13 Fig. 7.4 – Substrate-level phosphorylation.
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14 OK, take a deep breath and get ready to submerge yourself!
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15 Oxidation of Glucose The complete oxidation of glucose proceeds in stages: 1. Glycolysis 2. Pyruvate oxidation 3. Krebs cycle 4. Electron transport chain & chemiosmosis
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ch 7 lecture - Chapter 7: Harvesting the fixed energy of...

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