Chapter 9-Oxidation and ReductionOxidation: Removal of electronsReduction: Adding of electronsReducing Agent: Electron DonorOxidizing Agent: Electron AcceptorOxidation of organic moleculesLead to lose of C-H or C-C covalent bonds (oxidation of glucose releases energy from ATP)Exergonic, -Delta G, SpontaneousReduction or organic moleculesLead to gain of C-H or C-C covalent bonds.Endergonic, +Delta G, Nonspontaneous-Concept 9.1: Catabolic pathways yield energy by oxidizing organic fuelsSeveral processes are central to cellular respiration and related pathways.Breakdown of organic molecules is exergonic.Fermentation: Partial degradation of sugars that occurs without oxygen.Aerobic respiration: consumes organic molecules and oxygenAnaerobic Respiration is similar to aerobic respiration but consumes everything but oxygen.Cellular respiration: both anaerobic and aerobic often refers to aerobic-Redox ReactionsRelease energy is used to synthesize ATPAssembled from ADP + P using free energy from oxidation of glucose.-Oxidation of organic fuel during cellular respirationFuel (Glucose) is oxidized and oxygen is reduced.Carbon Dioxide is produced from oxidation of glucose and not reduction of oxygen.-NAD+Electrons from organic compounds are usually first transferred to NAD+ (Nicotinamide Adenine Dinucleotide)Is an electron acceptor, NAD+ functions as an oxidizing agent during cellular respirationNADH passes the electrons to the electron transport chain.Passes in a series of steps instead of one explosive step.-Stages of Cellular respirationHarvesting Energy from Glucose1) Glycolysis (Breaks down glucose into two molecules of pyruvate)2) Citric Acid Cycle (Completes breakdown of glucose)3) Oxidative Phosphorylation (Accounts for most of ATP synthesis, about 90%, 32 molecules) Smaller amount of ATP is harvested from glycolysis and citric acid cycle bysubstrate level phosphorylation.-Concept 9.2: GlycolysisSplitting of sugar into two molecules of pyruvateGlycolysis occurs (with or without oxygen) in cytoplasm and has two major phases.1) Energy Investment phasea. 2 ATP (One by Hexokinase another by Phosphofructokinase). 2) Energy Payoff Phasea. 4 ATP made (Two by phosphoglycerokinase, and another 2 by pyruvatekinase) -Results of GlycolysisPartial oxidation of glucose forms 2 pyruvic acid molecules (Loss of C-H, and C-C bonds) Electrons removed from glucose by oxidation are added to the electron carrier NAD+ (2 NAD+ are reduced to 2 NADH)Energy releases by partial oxidation of glucose converts 2ADP to 2 ATP molecules.Summary1) 2 pyruvate molecules + 2H2O Molecules.2) 2 ATP Molecules3) 2NAD+ NADH-Concept 9.3: After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic moleculesIn the presence of oxygen pyruvate enters the mitochondria where oxidation of glucose is complete-Oxidation of pyruvate to Acetyl CoABefore the citric cycle begins, pyruvate must be converted to acetyl CoA which links glycolysis to the citric acid cycle.A multienzyme complex that catalyzes three reactions carries out this stepOne pyruvate molecules is used to produce Acetyl CoA the byproduct of the process include:1) NADH + HCNA (NAD+ is reduced)2) CO2-Citric Acid CycleThe citric acid cycle also called the Krebs cycle completes the break down of pyruvate to carbon dioxide.Takes place within the mitochondrial matrixThe cycle oxidizes organic fuel derived from pyruvate, secreting 1 ATP, 3NADH, and 1 FADH2 per turn.Partial oxidation breaks C-C bonds and releases CO2 Electrons from oxidation of pyruvic acid are added to NAD+ and FAD+ to form NADH and FADH2 respectively.1 ATP is assembled from ADP + PO4 from energy released by oxidation.Since 1 molecule of glucose produces 2 molecules of pyruvic acid, 2 Acetyl CoA molecules enter the cycle and produces 2 ATP, 6 NADH, and 2 FADH2 and 4 CO2 per turn.Citric Acid cycle has 8 steps, each catalyzed by a specific enzyme.The Acetyl group of Acetyl CoA begins the cycle by combining with oxaloacetate, forming citrate.Next seven steps decompose the citrate back to oxaloacetate making the process a cycle.The NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport.-The Pathway of Electron TransportElectron Transport Chain (ETC is in the inner membrane Cristae) of the mitochondria.Most of the chains components are proteins, which exist, in multiprotein complexesThe carriers alternated reduced and oxidized states as they accept and donate electrons.Electrons drop in free energy as they go down the chain and are finally passed to oxygen forming a water molecule.Electrons are transferred from NADH (from stage 2 and electron shuttled form stage 1) or FADH2 (From stage 2) to the electron transport chain. Electrons are passed through a number of proteins including cytochromes (each with an iron atom) to oxygen.The ETC generates no ATP directlyChains function is to break the large free-energy drop from good to oxygeninto smaller steps that release manageable amounts of energy.-Chemiosmosis: The Energy Coupling MechanismElectrons transfer on the ETC causes proteins to Pump H+ from the mitochondrial matrix to the intermembrane space.This concentrates H+ in the intermembrane space.H+ then moves back across the membrane, passing through the protein, ATP synthase.ATP synthase uses the exergonic flow of H+ in the matrix to drive the phosphorylation of 26-28 ATPThis is an example of chemiosmosis, the use of energy in a H+ gradient to drive cellular work.The energy stored in a H+ gradient across membrane couples the redox reactions of the ETC to ATP synthesis.H+ gradient is referred to as a proton-motive force, emphasizing its capacity to do work.At the end of the ETC, FAD and NAD+ are reformed (reused in the citric acid cycle) Electrons leaving at the end of the ETC are added to 2H+ and ½ O2 to produced H2O. This is why oxygen is needed, to be the final electron acceptor.-An accounting of ATP production by cellular respirationDuring cellular respiration most energy flows in this sequence:Glucose NADH ETCProton-motive forceATP34% of the energy in a glucose molecule is transferred to ATP during cellular respiration, making 30-32 ATP (2 from Stage 1, 2 from stage 2, 26-28 atom stage 3)-Versatility of
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