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Biology 201 Ch 6 PowerPoint
- 1. Chapter 06 Lecture and AnimationOutline Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. See separate PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes and animations. To run the animations you must be in Slideshow View. Use the buttons on the animation to play, pause, and turn audio/text on or off. Please Note: Once you have used any of the animation functions (such as Play or Pause), you must first click on the slide’s background before you can advance to the next slide.
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- 3. 3 Flow of Energy •Thermodynamics – Branch of chemistry concerned with energy changes • Cells are governed by the laws of physics and chemistry
- 4. • Energy –capacity to do work – 2 states 1. Kinetic – energy of motion 2. Potential – stored energy – Many forms – mechanical, heat, sound, electric current, light, or radioactivity – Heat the most convenient way of measuring energy • 1 calorie = heat required to raise 1 gram of water 1ºC • calorie or Calorie? 4
- 5. 5 a. Potential energyb. Kinetic energy Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
- 6. • Energy flowsinto the biological world from the sun • Photosynthetic organisms capture this energy • Stored as potential energy in chemical bonds 6
- 7. 7 Redox reactions • Oxidation –Atom or molecule loses an electron • Reduction – Atom or molecule gains an electron – Higher level of energy than oxidized form • Oxidation-reduction reactions (redox) – Reactions always paired
- 8. 8 Copyright © TheMcGraw-Hill Companies, Inc. Permission required for reproduction or display. e– A B A + B +A+ B– Loss of electron (oxidation) Gain of electron (reduction) Lower energy Higher energy
- 9. Laws of thermodynamics •First law of thermodynamics – Energy cannot be created or destroyed – Energy can only change from one form to another – Total amount of energy in the universe remains constant – During each conversion, some energy is lost as heat 9
- 10. 10 • Second lawof thermodynamics – Entropy (disorder) is continuously increasing – Energy transformations proceed spontaneously to convert matter from a more ordered/less stable form to a less ordered/ more stable form
- 11. Copyright © TheMcGraw-Hill Companies, Inc. Permission required for reproduction or display. Disorder happens spontaneously Organization requires energy © Jill Braaten
- 12. 12 Free energy • G= Energy available to do work • G = H – TS H = enthalpy, energy in a molecule’s chemical bonds T = absolute temperature S = entropy, unavailable energy
- 13. ΔG = ΔH– TS • ΔG = change in free energy • Positive ΔG – Products have more free energy than reactants – H is higher or S is lower – Not spontaneous, requires input of energy – Endergonic • Negative ΔG – Products have less free energy than reactants – H is lower or S is higher or both – Spontaneous (may not be instantaneous) – Exergonic 13
- 14. 14 Copyright © TheMcGraw-Hill Companies, Inc. Permission required for reproduction or display. a. b. 0 0 Course of Reaction Products ∆ G > 0 ∆ G < 0 Reactants Reactants Course of Reaction Products FreeEnergy(G) EnergyReleasedEnergySupplied FreeEnergy(G) EnergyReleasedEnergySupplied Energy is released Energy must be supplied Exergonic Endergonic
- 15. Activation energy • Extraenergy required to destabilize existing bonds and initiate a chemical reaction • Exergonic reaction’s rate depends on the activation energy required – Larger activation energy proceeds more slowly • Rate can be increased 2 ways 1.Increasing energy of reacting molecules (heating) 2.Lowering activation energy 15
- 16. 16 Copyright © TheMcGraw-Hill Companies, Inc. Permission required for reproduction or display. ΔG EnergyReleasedEnergySupplied FreeEnergy(G) Activation energy Activation energy0 uncatalyzed catalyzed Course of Reaction Product Reactant
- 17. Catalysts • Substances thatinfluence chemical bonds in a way that lowers activation energy • Cannot violate laws of thermodynamics – Cannot make an endergonic reaction spontaneous • Do not alter the proportion of reactant turned into product 17
- 18. 18 Copyright © TheMcGraw-Hill Companies, Inc. Permission required for reproduction or display. ΔG EnergyReleasedEnergySupplied FreeEnergy(G) Activation energy Activation energy0 uncatalyzed catalyzed Course of Reaction Product Reactant
- 19. 19 ATP • Adenosine triphosphate •Chief “currency” all cells use • Composed of – Ribose – 5 carbon sugar – Adenine – Chain of 3 phosphates • Key to energy storage • Bonds are unstable • ADP – 2 phosphates • AMP – 1 phosphate – lowest energy form
- 20. 20 Copyright © TheMcGraw-Hill Companies, Inc. Permission required for reproduction or display. AMPCORE O O– O O O H H H H O CC N N N C N C CH H P O– O P O P O ADP ATP Triphosphate group O– CH2 High-energy bonds a. Adenine NH2 Ribose OHOH b.
- 21. 21 ATP cycle • ATPhydrolysis drives endergonic reactions – Coupled reaction results in net –ΔG (exergonic and spontaneous) • ATP not suitable for long-term energy storage – Fats and carbohydrates better – Cells store only a few seconds worth of ATP
- 22. 22 Copyright © TheMcGraw-Hill Companies, Inc. Permission required for reproduction or display. + + Pi Energy from exergonic cellular reactions ATP H2O ADP Energy for endergonic cellular processes
- 23. 23 Enzymes: Biological Catalysts •Most enzymes are protein – Some are RNA • Shape of enzyme stabilizes a temporary association between substrates • Enzyme not changed or consumed in reaction • Carbonic anhydrase – 200 molecules of carbonic acid per hour made without enzyme – 600,000 molecules formed per second with enzyme
- 24. 24 Copyright © TheMcGraw-Hill Companies, Inc. Permission required for reproduction or display. Active site a. b. Enzyme Enzyme–substrate complex Substrate
- 25. Active site • Pocketsor clefts for substrate binding • Forms enzyme–substrate complex • Precise fit of substrate into active site • Applies stress to distort particular bond to lower activation energy – Induced fit 25
- 26. 26 Copyright © TheMcGraw-Hill Companies, Inc. Permission required for reproduction or display. 1. The substrate, sucrose, consists of glucose and fructose bonded together. 2. The substrate binds to the active site of the enzyme, forming an enzyme– substrate complex. 3. The binding of the substrate and enzyme places stress on the glucose– fructose bond, and the bond breaks. 4. Products are released, and the enzyme is free to bind other substrates. Bond Glucose Fructose Active site Enzyme sucrase H2O
- 27. 27 Please note thatdue to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.
- 28. 28 • Enzymes maybe suspended in the cytoplasm or attached to cell membranes and organelles • Multienzyme complexes – subunits work together to form molecular machine – Product can be delivered easily to next enzyme – Unwanted side reactions prevented – All reactions can be controlled as a unit
- 29. 29 Nonprotein enzymes • Ribozymes •1981 discovery that certain reactions catalyzed in cells by RNA molecule itself 1. 2 kinds 1. Intramolecular catalysis – catalyze reaction on RNA molecule itself 2. Intermolecular catalysis – RNA acts on another molecule
- 30. Enzyme function • Rateof enzyme-catalyzed reaction depends on concentrations of substrate and enzyme • Any chemical or physical condition that affects the enzyme’s three-dimensional shape can change rate – Optimum temperature – Optimum pH 30
- 31. 31 Copyright © TheMcGraw-Hill Companies, Inc. Permission required for reproduction or display. a. b. RateofReaction Optimum pH for pepsin RateofReaction pH of Reaction Optimum pH for trypsin 1 2 3 4 5 6 7 8 9 30 40 50 60 70 80 Temperature of Reaction (˚C) Optimum temperature for human enzyme Optimum temperature for enzyme from hotsprings prokaryote
- 32. 32 Inhibitors • Inhibitor –substance that binds to enzyme and decreases its activity • Competitive inhibitor – Competes with substrate for active site • Noncompetitive inhibitor – Binds to enzyme at a site other than active site – Causes shape change that makes enzyme unable to bind substrate
- 33. 33 a. Competitive inhibitionb. Noncompetitive inhibition Enzyme Enzyme Allosteric site Active site Competitive inhibitor interferes with active site of enzyme so substrate cannot bind Allosteric inhibitor changes shape of enzyme so it cannot bind to substrate Active site Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Substrate Substrate Inhibitor Inhibitor
- 34. 34 Allosteric Enzymes • Allostericenzymes – enzymes exist in active and inactive forms • Most noncompetitive inhibitors bind to allosteric site – chemical on/off switch • Allosteric inhibitor – binds to allosteric site and reduces enzyme activity • Allosteric activator – binds to allosteric site and increases enzyme activity
- 35. 35 Metabolism • Total ofall chemical reactions carried out by an organism • Anabolic reactions/anabolism – Expend energy to build up molecules • Catabolic reactions/catabolism – Harvest energy by breaking down molecules
- 36. 36 Biochemical pathways • Reactionsoccur in a sequence • Product of one reaction is the substrate for the next • Many steps take place in organelles
- 37. 37 Copyright © TheMcGraw-Hill Companies, Inc. Permission required for reproduction or display. Initial substrate Intermediate substrate A Intermediate substrate B Intermediate substrate C End product Enzyme1 Enzyme2 Enzyme3 Enzyme4
- 38. Feedback inhibition • End-productof pathway binds to an allosteric site on enzyme that catalyzes first reaction in pathway • Shuts down pathway so raw materials and energy are not wasted 38
- 39. 39 Copyright © TheMcGraw-Hill Companies, Inc. Permission required for reproduction or display. a. b. Enzyme 1 Enzyme 2 Enzyme 3 Enzyme 1 Enzyme 2 Enzyme 3End product End product Initial substrate Intermediate substrate A Intermediate substrate B Initial substrate
- 40. 40 Please note thatdue to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.