Cellular Pathways that Harvest Chemical Energy : Respiration.
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Transcript of Cellular Pathways that Harvest Chemical Energy : Respiration.
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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 EnergyEach 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 EnergyTCA 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 SynthesisATP 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
MechanismCouples 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
FeedbackExcess 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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SummaryPhotosynthesis 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 134-135 for a detailed summary