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Published byCamilla Lamb Modified over 9 years ago
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Cellular Pathways that Harvest Chemical Energy : Respiration
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Energy flow and chemical recycling
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Energy For Life Photosynthesis stores chemical energy into chemical bonds and Respiration releases the energy stored in the chemical bonds ATP is the biological currency of Energy
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Oxidation and Reduction
Gain of one or more electrons by an atom, ion or molecule is called Reduction Oxidation and Reduction always occurs together, one material is oxidized (loss E) and other is Reduced (Gain E)
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Oxidized and Reduced NAD
Coenzyme NAD is a key electron carrier in the redox Rxn
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NAD+ as an electron shuttle
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Energy Carrier Oxidizing agent (NAD) accepts E in the process of oxidizing the reducing agent (AH2 to A). Oxidizing agent (NAD) becomes reduced (NADH). Reducing agent donates E and becomes Oxidized as it reduces the Oxidizing agent (B to BH2)
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Cellular Energy Pathways
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Overview of cellular respiration
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Glycolysis and Fermentation
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Changes in Free Energy Each step in glycolysis changes the free energy available Thus after the step 6 each following steps and metabolites or products will have less energy First you invest energy then harvest it……
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Glycolysis: Glucose to Pyruvate
The energy-investing reactions/phase of Glycolysis
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Glycolysis: Glucose to Pyruvate
Energy-harvesting reactions/phase yields ATP and NADH Pl note that step 5… each molecule is 2 units because 6C are splits into two 3C molecules Step 6 to 7 is a substrate-level phosphorylation
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Substrate-level phosphorylation
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Glu to Pyr Step 9 to 10 is also a SLP
Glycolysis nets two Molecules of ATP and two Molecules of NADH 4ATP-2ATP=2ATP In fermentation the net yield is only 2 ATP
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Pyruvate Oxidation (Mito)
PDC is a large complex, Pyruvate DH converts Pyruvate to Acetyl CoA, releasing first Carbon dioxide Pyruvate is Oxidized to acetyl group, E conserved in NADH and some energy is conserved by comining acetyl group to CoA
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Pyruvate to acetyl CoA
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Citric Acid or TCA Cycle
Acetyl CoA enters the TCA cycle, and CoA regenerated
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TCA Cycle
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Closer look at TCA cycle
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Summary of TCA cycle
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Free Energy TCA cycle releases more energy than Glycolysis or pyruvate reduction
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Oxidation of NADH + H+
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Resp Chain
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Chemiosmotic Mechanism
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ATP Synthesis ATP synthesis is a reversible reaction and ATP synthase can also act as an ATPase hydrolyzing ATP to ADP Exergoic Rxn from Et drive the Electrogenic pumping of protons out of Mitochondria into IM space Pot E of proton gradient has two role, act as channel for protons to diffuse back and it uses E of diffusion to make ATP
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Chemi-osmotic Mechanism
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Chemi-osmotic Mechanism
Couples ET to the ATP synthesis using ATP synthase using a Proton Gradient
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Lactic Acid Fermentation
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Alcoholic Fermentation
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Cellular Respiration Theoretical Net ATP yield from the complete oxidation each glucose molecule is 36 ATP, but never in a living system
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Cellular Respiration
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Cellular Respiration
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ATP molecules during cellular respiration
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Relationship among the other major Metabolic Pathways
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Catabolism of various food molecules
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Coupling Metabolic Pathways
OAA and Asp interconverts, is called Transamination
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Regul by Negative and Positive Feedback
Excess accumulation of some products can shut down their synthesis or stimulate synthesis of other products
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Feedback Regulation Citrate and ATP inhibits PFK thus Glycolysis
ADP and AMP stimulates Glycolysis
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Feedback Regulation ATP and NADH inhibits TCA cycle
Citrate stimulates FA-CoA Rxn NAD and ADP activated ICDH ATP and NADH inhibits KGADH
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Control of cellular respiration
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Energy flow and chemical recycling
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Summary Photosynthesis places energy into chemical bonds and respiration releases it Glycolysis, TCA cycle,and ET chain and ATP synthesis Fermentation of pyruvate to lactate or ethanol Oxidation reduction reactions Chemiosmotic synthesis of ATP using a proton gradient Regulation of Metabolic pathways by positive and negative feedback Various metabolic pathways inter-communicate with each other Pl read pages for a detailed summary
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