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Energy: the capacity to effect change BCOR 011 Lecture 11 Two types of energy Chapter 8 The Flow of Energy in a Cell Sept 26, 2005 Potential Energy Kinetic Energy -stored in height -energy of movement -stored in battery (conc/charge) -stored in BONDS -molecules colliding, vibrating -HEAT, light 1 2 Figure 8.1 1st Law of Thermodynamics Potential Energy Stored in: Figure 8.2 location Energy is neither created nor destroyed in chemical reactions but only Transformed from one form to another Figure 8.5 On the platform, a diver Diving converts potential has more potential energy. energy to kinetic energy. Chemical bonds Potential Potential Kinetic Kinetic gradient Climbing up converts kinetic energy of muscle movement to potential energy. In the water, a diver has less potential energy. 3 4 In a chemical reaction products have a lower potential energy than reactants a Chemical Reaction Atoms bonded in High Potential Energy Configuration Example - - Energy is Released H H-C-H H Atoms bonded in Low Potential Energy Configuration Reorganization of Bonds of existing molecules - an exchange O=C=O O=O H O=O Same # of H’s Same # of C’s Same # of O’s O H H H - H-C-H H 6 Energy that is released: reduced Has the capacity to DO WORK O=O Raise potential state of something else O=C=O H O H ENERGY RELEASED Or effect movement – heat, motion oxidized Low Energy 7 H All Start with filled outer shell of electrons All End with outer shell of electrons 5 High Energy O 8 Other Types of Work Types of Work: 1 Biosynthetic: changes in chemical bonds A + B 2. Chemical Concentration Gradient C + D products reactants A+B G+H E+F C+D Ainside + Boutside even even even low high 9 3. Electrical work – movement of ions across a membrane against an electrochemical gradient Ainside + Boutside even Aoutside + Binside 10 Other Types of Work Aoutside + Binside + - 11 4 Mechanical Work: Movement, Motility 12 • Some organisms Another form of MOVEMENT Relaxed Low Energy Conformation A – Convert energy to light, as in bioluminescence Conformation B Poised 13 High Energy Figure 8.1 Change In potential Energy Energy that is released: State 1 Has the capacity to DO WORK Raise potential state of something else Or effect movement – heat, motion But some is always lost to disorder State 2 Gross Pay 15 14 Released Energy Ability To do + Randomness work Take Home + Pay Taxes 16 Kinetic Energy can be dissipated: Second law of Thermodynamics: Randomized Releases Energy Kinetic Energy Ch an ce of Sound Floor Vibration go ing in RE Requires Energy Input VE RS E? Disorder The Universe is proceeding to a State of MAXIMUM DISORDER Only time this is not true is when no movement anymore ie. at abosolute zero 17 18 Change In potential Energy 0o K - no motion, no “taxes” State 1 A Progressive Scale: Higher the temperature, the more that disorder comes into play higher proportion of energy lost to randomness 19 State 2 Enthalpy ∆H Released Energy Ability To do + Randomness work Free Energy + ∆G Entropy T ∆S 20 ENTROPY ∆S (disorder) ENTHALPY ∆H Change in Chemical Bond Energy Freedom of Movement or Position Time 21 Number of possible states that can be present in: Change in Freedom Roll of “2” High Potential High Potential Randomness ENTROPY ∆S Change in Chemical Bond Energy ENTHALPY ∆H Low entropy Only 1 possible “state” Low Potential Glucose + 6 O2 6 CO2 + 6 H2O ENTROPY ∆S Few States Low Potential 6 Glucose 6 CO2 + + 6 O2 6 H2O Change in Freedom Many States “Dispersed” 22 Number of Possible States That can be Present in Few States Many States “Dispersed” time Roll of “7” High entropy -∆H 6 possible “states” 23 Na+ ClNaCl crystal ions in water Na+ ClNaCl crystal ions in water +∆S 24 Change in Chemical Bond Energy The Free Energy Change ∆G Dictates whether a reaction will Proceed spontaneously or not Energy that Goes to Do Useful Work Energy that Goes to Randomness Dependent On Entropy Temperature Enthalpy “free energy” (Gibb’s Free Energy) Kinetic Movement Whether a Reaction is ∆H Favorable or Unfavorable = T∆S ∆G 25 = + ∆H - If ∆G = negative # reaction is energetically favorable ∆G T∆ S “spontaneous” 26 An exergonic reaction – Proceeds with a net release of free energy and is spontaneous “will happen” Reactants Free energy Amount of energy released (∆G <0) Energy Products ∆G = ∆H – T∆S - ∆G is favorable exergonic “spontaneous” + ∆G is NOT favorable, endergonic, endergonic, nonspontaneous27 Progress of the reaction 28 Figure 8.6 (a) Exergonic reaction: free energy released An endergonic reaction 2 Factors Contribute to Whether a Reaction will Occur: – Is one that absorbs free energy from its surroundings and is nonspontaneous change in Bond Energy “doesn’t happen” Reduced change in Entropy Complex Free energy Products Amount of energy released (∆G>0) Energy Oxidized Reactants The sum of these is the Progress of the reaction Figure 8.6 Complex change in Entropy Lower 8 fats H H-C-H H H R-C-OH H alcohol 30 EXERGONIC REACTIONS gasoline burns iron rusts hydrogen and oxygen form water (explosive!) Either: go to bonding arrangement with lower potential energy O = sugars R-C-H aldehyde O = change in Bond Energy hydrocarbon net ENERGY RELEASED - EXERGONIC = FAVORABLE If require net ENERGY INPUT - ENDERGONIC = UNFAVORABLE Simple Reduced (no oxygens) H H HHH HH H H-C-C-C-C-C-C-C-C-H H HH HH HH H Net Useful Energy (∆ (∆G) If (b) Endergonic reaction: energy required 29 High Simple R-C-OH Final product acid Or: go from a more complex state to a simpler state 1 molecule of 8 carbons vs 8 molecules of 1 carbon O=C=O Low Oxidized Carbon 31 dioxide Lowest 32 ∆H= ∆S= + ∆G= very - favorable favorable favorable 2 Spontaneous 33 Favorable - it can happen ∆H= ∆S= ∆G= Unfavorable + + Very favorable favorable Entropy Driven Reaction Spontaneous Favorable - it can happen 35 Entropy overwhelms Enthalpy ∆H = Hproducts -Hreactants − ∆H exothermic Heat released + ∆H endothermic Heat input icepack 34 ∆H= ∆S= ∆G= - very favorable unfavorable favorable Enthalpy Driven Reaction Spontaneous Favorable - it can happen 36 Enthalpy overweighs Entropy ∆H= ∆S= ∆G= ∆G = ∆H – T∆S ∆G = ∆H – T∆S ∆G = ∆H – T∆S (-) - (+) (- ) - (- ) (+) - (+) Spontaneous Enthalpically Entropically 37 Favorable Rxn Driven Rxn Driven Rxn A typical ENDERGONIC/Unfavorable/NonSpontaneous REACTION - building a polymer Monomer + Monomer + + unfavorable unfavorable unfavorable Non-spontaneous NOT Favorable - it can NOT happen 38 COUPLED Reactions Tie a favorable rxn with An otherwise unfavorable rxn Polymer + Water Requires 5.5 energy units WILL NOT OCCUR How could we make it occur? If have a captured packet of energy of 7.3 energy units Integrate an exergonic reaction with an endergonic reaction 39 Drive otherwise unfavorable reactions 40 ∆G = +5.5 kcal/mole 1. 2. ATP+ H2O ADP + Pi ATP ∆G = -7.3 kcal/mole ADP + Pi Favorable or unfavorable41 ? Coupled Reaction ADP -P (ATP) Note: Each step is favorable ∆G = -7.3 kcal/mole +∆G = +5.5 kcal/mole Net rxn ∆G = -1.8 kcal/mole 42 Another Example of a Coupled Reaction + monomer1 ADP-monomer1 + P Endergonic reaction: ∆G is positive, reaction is not spontaneous I’m free! ∆G = -1.0 ADP-monomer1 + monomer 2 NH2 Now tied together Glu ADP + Glutamic acid monomer1-monomer 2 Now I’m free too! ∆G = -0.8 7.3 units released Net: ATP +H2O monomer1 + monomer2 5.5 units needed + NH3 Glu Ammonia Glutamine ∆G = +3.4 kcal/mol Exergonic reaction: ∆ G is negative, reaction is spontaneous ATP ADP + P monomer1-monomer2 + H2O DO NOT LET ATP FALL APART IN 1 STEP, use energy in its bond to MAKE the polymer linkage 43 Figure 8.10 + H2 O ADP + Coupled reactions: Overall ∆G is negative; together, reactions are spontaneous P ∆G = + 7.3 kcal/mol ∆G = –3.9 kcal/mol 44 Three types of cellular work powered by ATP hydrolysis Physical movement P Equilibrium Reactions in a closed system i P Motor protein Driving Conformational Changes ADP Of + P Proteins Protein moved (a) Mechanical work: ATP phosphorylates motor proteins Membrane protein ActiveATP Transport Pumps – Eventually reach equilibrium ∆G < 0 ∆G = 0 i P Solute P i Solute transported (b) Transport work: ATP phosphorylates transport proteins P Glu + NH2 NH3 Reactants: Glutamic acid and ammonia Figure 8.11 + P Glu i Product (glutamine) made Biosynthetic Coupled Rxn45 Figure 8.7 A (a) A closed hydroelectric system. Water flowing downhill turns a turbine that drives a generator providing electricity to a light bulb, but only until the system reaches equilibrium. 46 (c) Chemical work: ATP phosphorylates key reactants In living systems cellular respiration is a series of favorable reactions – Experience a constant flow of materials in – Constant Energy Input ∆G < 0 ∆G < 0 ∆G < 0 ∆G < 0 (b) An open hydroelectric system. Flowing water keeps driving the generator because intake and outflow of water keep the system from reaching equlibrium. Figure 8.7 Figure 8.7 47 (c) A multistep open hydroelectric system. Cellular respiration is analogous to this system: Glucoce is brocken down in a series of exergonic reactions that power the work of the cell. The product of each reaction becomes the reactant for the next, so no reaction reaches equilibrium. 48 Summary: For example, oxidation of glucose: C6H12O6 (glucose) + 6O2 6CO2 + 6H2O -matter is neither created nor destroyed -the universe is proceeding toward disorder ∆G= -686 kcal/mol ∆H = -673 kcal/mol ∆H = enthalpy (heat content,bond energy) T∆S= -13 kcal/mol ∆S = entropy (randomness) in the cell, this is done in >21 steps! ∆G = free energy (available to do work) Capture the energy in small packets ∆G = ∆H - T∆S ie, 36 ATP units of 7.3 kcal - coupled reactions 49 -biological systems always need constant energy input 50