Chapter 9 – Cellular respiration Key ConceptsSlide 2The Citric Acid CycleThe Substrates of the Citric Acid CycleSlide 5The Citric Acid Cycle Regulation and SummaryGlucose Oxidation SummaryFree Energy Changes, NADH, and FADH2Slide 9The Electron Transport ChainOxidative PhosphorylationElectron Transport and ChemiosmosisSlide 13The Chemiosmotic HypothesisSlide 15Slide 16How Is the Electron Transport Chain Organized?Slide 18ATP Synthase StructureSlide 20ATP Yield from Cellular RespirationUncoupled mitochondria in brown fat produce heat:Uncouplers  No proton gradientAerobic and Anaerobic RespirationOxygen as a Final Electron AcceptorSlide 26FermentationDifferent Fermentation PathwaysSlide 29Fermentation and Cellular Respiration EfficiencyCellular Respiration Interacts with Metabolic PathwaysSlide 32Processing Proteins and Fats as FuelSlide 34Anabolic Pathways Synthesize Key MoleculesFatty acid (FA) Oxidation: Not coveredFine turning of metabolic processes in multi cellular organisms takes place via action of Hormones:Main metabolic pathways:© 2011 Pearson Education, Inc.Chapter 9 – Cellular respiration Key Concepts In cells, the endergonic reactions needed for life are paired with exergonic reactions requiring ATP.Cellular respiration produces ATP from molecules with high potential energy – often glucose.Cellular respiration has four components: 1. Glycolysis 2. Pyruvate processing3. The citric acid cycle4. Electron transport and chemiosmosisRespiration and fermentation are carefully regulated.Fermentation pathways allow glycolysis to continue when the lack of an electron acceptor shuts down electron transport chains.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.The Citric Acid Cycle •During the third step of glucose oxidation, the acetyl CoA produced by pyruvate processing enters the citric acid cycle, located in the mitochondrial matrix.–Each acetyl CoA is oxidized to two molecules of CO2. •Some of the potential energy released is used to1. Reduce NAD+ to NADH. 2. Reduce flavin adenine dinucleotide (FAD) to FADH2 (another electron carrier). 3. Phosphorylate GDP to form GTP (later converted to ATP).© 2011 Pearson Education, Inc.The Substrates of the Citric Acid Cycle•A series of carboxylic acids is oxidized and recycled in the citric acid cycle  8 enzymatic reactions•Citrate (the first molecule in the cycle) is formed from pyruvate and oxaloacetate (the last molecule in the cycle).•The citric acid cycle completes glucose oxidation. The energy released by the oxidation of one acetyl CoA molecule is used to produce 3 NADH, 1 FADH2, and 1 GTP, which is then converted to ATP.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.The Citric Acid Cycle Regulation and SummaryThe citric acid cycle can be turned off at multiple points, via several different mechanisms of feedback inhibition. To summarize, the citric acid cycle starts with acetyl CoA and ends with CO2. The potential energy that is released is used to produce NADH, FADH2, and ATP. When energy supplies are high, the cycle slows down.© 2011 Pearson Education, Inc.Glucose Oxidation Summary•Glucose oxidation produces ATP, NADH, FADH2, and CO2. •Glucose is completely oxidized to carbon dioxide via glycolysis, the subsequent oxidation of pyruvate, and then the citric acid cycle. •In eukaryotes, glycolysis occurs in the cytosol; pyruvate oxidation and the citric acid cycle take place in the mitochondrial matrix.© 2011 Pearson Education, Inc.Free Energy Changes, NADH, and FADH2•For each glucose molecule that is oxidized to 6 CO2, the cell reduces 10 molecules of NAD+ to NADH and 2 molecules of FAD to FADH2, and produces 4 molecules of ATP by substrate-level phosphorylation.•The ATP can be used directly for cellular work.•However, most of glucose’s original energy is contained in the electrons transferred to NADH and FADH2, which then carry them to oxygen, the final electron acceptor.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.The Electron Transport Chain•During the fourth step in cellular respiration, the high potential energy of the electrons carried by NADH and FADH2 is gradually decreased as they move through a series of redox reactions. •The proteins involved in these reactions make up what is called an electron transport chain (ETC).•O2 is the final electron acceptor. The transfer of electrons along with protons to oxygen forms water.© 2011 Pearson Education, Inc.Oxidative Phosphorylation •The energy released as electrons move through the ETC is used to pump protons across the plasma membrane into the intermembrane space, forming a strong electrochemical gradient.•The protons then move through the enzyme ATP synthase, driving the production of ATP from ADP and Pi. •Because this mode of ATP production links the phosphorylation of ADP with NADH and FADH2 oxidation, it is called oxidative phosphorylation.© 2011 Pearson Education, Inc.Electron Transport and Chemiosmosis•Most of the ETC molecules are proteins containing chemical groups that facilitate redox reactions. All but one of these proteins are embedded in the inner mitochondrial membrane. –In contrast, the lipid-soluble ubiquinone (Q) can move throughout the membrane.•During electron transport, NADH donates electrons to a flavin-containing protein at the top of the chain, but FADH2 donates electrons to an iron-sulfur protein that passes electrons directly to Q.© 2011 Pearson Education, Inc.The inner mitochondrial membrane is virtually impermeable to hydrogen ions (protons).© 2011 Pearson Education, Inc.The Chemiosmotic Hypothesis•The ETC pumps protons from the mitochondrial matrix to the intermembrane space. The proton-motive force from this electrochemical gradient can be used to make ATP in a process known as chemiosmosis.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.How Is the Electron Transport Chain Organized? •ETC proteins are organized into four large multiprotein complexes (called complex I–IV) and cofactors. Protons are pumped into the intermembrane space from the mitochondrial matrix by complexes I and IV. •Q and the protein cytochrome c transfer electrons between complexes. –Q also carries protons across the membrane.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.ATP Synthase Structure•ATP synthase is an enzyme complex consisting of two components:–An ATPase “knob” (F1 unit) –A