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26March2009NutritionMetabolismPOSTING

26March2009NutritionMetabolismPOSTING - PRS 1 Using the...

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PRS 1: Using the electron tower
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PRS 2: Using the electron tower
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Biosynthetic (Anabolic) reactions of the cell require Energy ( ATP ) and Electrons ( NADPH ); ATP / NADPH are provided by Catabolic rxns Energy must be provided to the anabolic reactions by ATP ; ATP is also used for cell motility, transport functions, etc. Electrons must be provided to the anabolic reactions by NADPH . ATP and NADPH are provided through Catabolic Reactions that extract energy and electrons from nutrients by oxidation / reduction reactions.
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e
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Basic ideas to understand metabolism: 1. Energy is related to work ; in biological systems work is involved with movement 2. Energy is also released/used in making/breaking chemical bonds ; to liberate energy an organism uses coupled redox reactions and traps that energy in ATP. 3. Oxidation/reduction reactions in organic molecules are accompanied by gain or loss of O or H . 4. Many redox reactions in biological systems have an intermediate molecule that acts as an “electron carrier”; NADH carries electrons in catabolic reactions and NADPH transfers electrons into anabolic reactions. 5. ATP is an energy carrier : cells make ATP by two mechanisms.
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Basic ideas to understand metabolism 4 Cell has carriers that are used as intermediates in redox reactions: What happens if react H 2 and O 2 ? KABOOM Some cells actually do this reaction, but don’t explode! e from donor intermediate e acceptor On reduction potentials table: see NAD + /NADH
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Oxidation/reduction in organic molecules Metabolism in lots of organisms can be summarized as: Glucose (C 6 H 12 O 6 ) + 6 O 2 6 CO 2 + 6 H 2 O ATP Notice the oxidation of the C from C–Hs to CO 2 . This is the important point.
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Specific example CH 3 CH 3 CH 3 H 2 C–OH CHO COOH Carbon is being oxidized in each step. So, what gets reduced? Ethanol acetaldehyde acetic acid
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Electron Carriers NAD + and a phosphorylated version NADP + act as intermediates that are electron carriers. The cell uses these electron carriers because they have reduction potential - see the electron tower (reduction potentials table). NAD = Nicotinamide adenine dinucleotide NAD is the Oxidized form of the electron carrier. (NADH+H + ) is the Reduced form of the electron carrier.
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Specific example CH 3 CH 3 CH 3 H 2 C–OH CHO COOH Ethanol acetaldehyde acetic acid NAD + NADH+H + NAD + NADH+H + 2 sets of redox reactions!
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