Lecture 8 – Evolution of Bioenergetics IText (Pgs. 578 – 583, Chapter 9)Terms from previous lectures- Exothermic and Endothermic- Endergonic and Exergonic- Gibbs Free Energy = ΔGo ΔG = ΔH – TΔHo Spontaneous reactions: - ΔG- Oxidation – Reduction reactions- Catabolic and Anabolico Catabolic reaction – break of a bond,liberate energy and increase entropyo Anabolic reaction – Complex moleculescreatedOrganisms and Energy- Organisms run redox reactions or capture sunlightto generate excited electronso The then capture some of the energy as theseelectrons return to their ground stateo This energy is stored in a few types of “highenergy” molecules- Table 27.4 – Electron Acceptors Metabolism – generation of useful energy- Use reactions that generate high energy electrons (e-)- Oxidize a high energy substrateo Oxidize means remove electronso Results in lower energy product molecule that accepts the electron(s)- How do you capture and use energy lost by e- during this process?Objective of Metabolism- Yield energy in a useful form most often as ATP- Metabolism is a link of exergonic reactionso Energy is stimulated electrons are held captive in ATP in cell energyo Remove the ATP releases energy (-enthalpy) and is more random (+ entropy)Why ATP?- Cells run reactions with enough Free Energy to make it!o Yields more than 7.3 kcal/mole- Energy given off by cleavage of terminal phosphate bond is sufficient to run cellular reactions; high potential energy!- Relatively stable- Uses molecules common to all cellso All cells have DNA and RNA- Evolutionary metabolic and other molecular adaptations based on energy from thiscommon molecule- Reasonably efficient yield of energy- Common mechanism of harvesting or using the energyan ATPo Forms a phosphorylated intermediateo Add a negatively charge PO4= to a molecule (e.g. a protein) and it changesshape or forms a high energy reactive form of the moleculeProducing ATP- 1st Strategy – Substrate-Level Phosphorylation (SLP) o Glycolysis and Fermentationo Low energy yield but common in (all?) organisms- 2nd Strategy – Chemiosmotic Synthesis Utilizing ElectronTransport Chainso How do e- transport chains generate ATP? Passed along protein chain- Localized and organized in membrane- e- changes shape of e- carrier proteins- Protons (H+) pumped creating ΔC and ΔEo POTENTIAL ENERGY- Protons then move through ATP synthaseto make ATPo It changes shape to bringADP and Pi together Chemiosmotic Synthesis Even bacteria use ETCs!Higgin’s Rule of Biology #3- Life is simply macromolecules changing shape Figure 9.7: NAD+ and NADHWhat picks up ~e- from the exergonic reactions? - First acceptor in e- transport chain - NAD+ + 2e- NADH + H+- NADP++ 2e- NADPH + H+- FAD + 2e- FADH2Why are we talking about energy and metabolism?What do I expect you to know and understand?Metabolic Diversity: Exciting e- to the top of ETCs- Phototrophso Use light energy to excite e-- Organotrophso Oxidize organic molecules which serve as e- donorso Exergonic (-ΔG) reactions- Lithotrophso Oxidize inorganic molecules (e.g. CH4 or NH3) which donate e-- Autotrophso Synthesize organic compoundso Reduction of C- Heterotrophso Utilize organic compounds made by autotrophsSummary Review- Organisms adapt to utilize environmental exergonic reactions- These yield excited electrons- ATP is the resulto Why ATP?o How does it work?o ETCso Proton pumpso ATP synthaseo Chemiosmotic
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