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Bioenergetics (Overview)

Anabolic. Catabolic. Bioenergetics (Overview). Metabolism (Overview). Metabolism = Catabolism + Anabolism. Catabolic reactions are energy yielding. They are involved in the breakdown of more-complex molecules into simpler ones. Anabolic reactions are energy requiring.

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Bioenergetics (Overview)

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  1. Anabolic Catabolic Bioenergetics (Overview)

  2. Metabolism (Overview) Metabolism = Catabolism + Anabolism Catabolic reactions are energy yielding They are involved in the breakdown of more-complex molecules into simpler ones Anabolic reactions are energy requiring They are involved in the building up of simpler molecules into more-complex ones

  3. Catabolic reaction Anabolic reaction Energy Coupling in Metabolism Catabolic Reactions provide the energy that drives Anabolic Reactions forward

  4. First Law of Thermodynamics: Organisms are Energy Transducers Energy can be neither created nor destroyed Therefore, energy “generated” in any system is energy that has been transformed from one state to another (e.g., chemically stored energy transformed to heat) Second Law of Thermodynamics: Efficiencies of energy transformation never equal 100% Therefore, all processes loseenergy, typically as heat, and are not reversible unless the system is open & the lost energy is resupplied from the environment Conversion to heat is the ultimate fate of chemical energy

  5. Organisms are Energy Transducers

  6. Organisms are Energy Transducers Organisms take in energy & transduce it to new forms (1st law) As energy transducers organisms are <100% efficient (2nd law) Organisms employ this energy to: • Grow • Protect Themselves • Repair Themselves • Compete with other Organisms • Make new Organisms (I.e., babies) In the process, organisms generate waste chemicals & heat Organisms create local regions of order at the expense of the total energy found in the Universe!!! We are Energy Parasites!

  7. Gravity (center Earth) Waste Heat (once reaches Bottom) Potential Energy Energy (a reminder) “Kinetic” Kinetic Energy

  8. What is the name of this molecule? Free Energy & Spontaneity

  9. Source of Energy Spontaneous Reaction Non-spontaneous Reaction Free Energy & Spontaneity Rather than lighting bulbs, in most biological systems incoming energy is either stored or is used to produce ATP

  10. Energy for Anabolism Energy Coupling via ATP (1/2)

  11. Hydrolysis of ATP

  12. Energy Coupling via ATP (2/2)

  13. Energy Coupling by Pi Transfer

  14. Exergonic Reaction (Spontaneous) • Decrease inGibbs free energy (-G) • Increase in stability Overview • Spontaneous (gives off net energy upon going forward) • Downhill (toward center of gravity well, e.g., of Earth) • Movement towards equilibrium • Coupled to ATP production (ADP phosphorylation) • Catabolism Endergonic Rxn (Non-Spontaneous) • Increase inGibbs free energy (+G) • Decrease in stability Overview • Not Spontaneous (requires net input of energy to go forward) • Uphill (away from center of gravity well, e.g., of Earth) • Movement away from equilibrium • Coupled to ATP utilization (ATP dephosphorylation) • Anabolism

  15. Low- (i.e., body-) Temperature Stability To be unstable, something must have the potential to change into something else, typically something that possesses less free energy To be unstable, releasing something’s ability to change into something else must also be relatively easy (i.e., little input energy) Why don't energy-rich molecules, e.g., glucose, spontaneously degrade into CO2 and Water? Therefore, Stability = already low free energy Alternatively, Stability = high activation energy Things, therefore, can be high in free energy but still quite stable, e.g., glucose

  16. Transition State

  17. Chemical Reaction Without Catalysts, Transition States are Achieved via an input of Heat, i.e., Higher Temperatures Activation Energy  Activation Energy  a.k.a., Substrate if enzyme catalyzed

  18. Chemical Reaction Note no change in degree of spontaneity, i.e., in G

  19. Catalyzed Reaction At a given temperature catalyzed Rxns can run faster because less energy is required to achieve the transition state

  20. Catalyzed Reaction

  21. Induced Fit (Active Site) The Catalysis associated with Enzymes occurs within small regions on (or within) proteins called Active Sites Induced Fit not only allows the enzyme to bind the substrate(s), but also provides a subtle application of energy (e.g., “bending” chemical bonds) that causes the substrate(s) to destabilize into the transition state

  22. Subtle Application of Energy

  23. Enzyme Catalytic Cycle • Input of Activation • Energy

  24. Mechanisms of Catalysis (1) Active sites can hold two or more substrates in proper orientations so that new bonds between substrates can form (2) Active sites can stress the substrate into the transition state (3) Active sites can maintain conducive physical environments (e.g., pH) (4) Active sites can participate directly in the reaction (e.g., forming transient covalent bonds with substrates) (5) Active sites can carry out a sequence of manipulations in a defined temporal order (e.g., step A  step B  step C)

  25. Polypeptide Mechanisms of Catalysis Metal Ion or = Organic Molecule = Organic Cofactor

  26. Product Substrate Enzyme Saturation Enzyme Activity at Saturation is a function of Enzyme Turnover Rate

  27. Enzyme Saturation

  28. Modification of Enzyme Activity Even at Saturation the rate of Enzymatic Reactions can be modified

  29. More-Subtle Inhibition of Active Sites (1/2)

  30. More-Subtle Inhibition (2/2)

  31. Multi-Subunit Enzymes (1/2)  Recall that a Multi-Subunit Enzyme is a catalytic Protein that consists of more than one Polypeptide This is a description of Allosteric Regulation (Inhibition)

  32. This is Cooperativity Multisubunit Enzymes (2/2) This also is a form of Allosteric Regulation (activation)

  33. Feedback Inhibition

  34. Energy-Metabolism Regulation

  35. Enzyme Localization Organization of Electron Transport Chain of Cellular Respiration: Substrate  Enzyme  Product  Enzyme chains are co-localized

  36. First Exam Next Wednesday The first exam is scheduled for next Wednesday This exam will cover chapters 2 through 6 (unit 1) Expect ~same # questions per class met That’s 7 classes x (3 to 5 questions/class) = 25 to 35 questions Study over the weekend (perhaps already having started?) Tuesday will be a recitation—bring questions!!!! The exam will start as soon as we can get in the room It’ll be limited in length by a need to get people to next classes

  37. First Exam Next Wednesday Let’s try to avoid the scholastic equivalent of this!

  38. Link to Next Presentation

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