Energy: the capacity to effect change Two types of energy BCOR 011 Lecture 11 Chapter 8 The Flow of Energy in a Cell Potential Energy Kinetic Energy -stored in height -energy of movement Sept 26, 2005 -stored in battery (conc/charge) -molecules colliding, vibrating -stored in BONDS -HEAT, light 1 2 Figure 8.1 Potential Energy Stored in: 1st Law of Thermodynamics Energy is neither created nor destroyed in chemical reactions but only Transformed from one form to another Figure 8.2 location Figure 8.5 On the platform, a diver Diving converts potential Chemical has more potential energy. energy to kinetic energy. bonds Potential Potential Kinetic Kinetic gradient In the water, a diver has Climbing up converts kinetic less potential energy. energy of muscle movement 3 4 to potential energy. In a chemical reaction a Chemical Reaction products have a lower potential energy than reactants Reorganization of Bonds of existing molecules Atoms bonded in -an exchange Example High Potential Energy Configuration O=C=O H- O=O Energy is Released Energy is Released H-C- -H O=O HH HH H O O Atoms bonded in Low Potential Energy Same # of H’s Configuration Same # of C’s All Start with filled outer shell of electrons Same # of O’s All End with outer shell of electrons 5 6 High Energy H -- Energy that is released: H-C-H reduced H Has the capacity to DO WORK O=O Raise potential state of something else ENERGY Or effect movement – heat, motion HH O=C=O O RELEASED oxidized Low Energy 7 8 Types of Work: Other Types of Work 1 Biosynthetic: changes in chemical bonds 2. Chemical Concentration Gradient A + B C + D reactants products A+B G+H Ainside + Boutside Aoutside + Binside E+F even even low high C+D 9 10 3. Electrical work – movement of ions across Other Types of Work a membrane against an electrochemical gradient Ainside + Boutside Aoutside + Binside even even + - 11 4 Mechanical Work: Movement, Motility 12 • Some organisms Another form of – Convert energy to light, as in bioluminescence MOVEMENT Relaxed Low Energy Conformation Conformation A B Poised Poised Figure 8.1 High Energy13 14 Change In potential Released Energy Energy that is released: Energy State 1 Has the capacity to DO WORK Ability To do + Randomness Raise potential state of something else Raise potential state of something else work State 2 Or effect movement – heat, motion State 2 Take But some is always lost to disorder Gross Pay Home + Taxes 15 Pay 16 Kinetic Energy can be dissipated: Randomized Second law of Thermodynamics: Releases Energy The Universe is proceeding to a Kinetic Energy Sound State of MAXIMUM DISORDER C ha nc Floor Vibration e of g oi ng i n RE VE Disorder RS Only time this is not true Requires E? Energy Input is when no movement anymore ie. at abosolute zero 17 18 Change 0o K - no motion, no “taxes” In potential Released Energy Energy State 1 Ability + Randomness A Progressive Scale: To do Higher the temperature, work the more that disorder comes into play State 2 higher proportion of energy lost to randomness Free Enthalpy Energy + Entropy 19 ∆H ∆G T∆S 20 ENTHALPY Change in ENTROPY Chemical Bond ENTHALPY ∆H Energy ∆H ∆S (disorder) Change in Chemical Bond Freedom of Chemical Bond Freedom of Time Energy Movement or Position High High Potential Potential -∆H Low Potential Low Potential Randomness Glucose 6 CO2 6 Glucose 6 CO2 + + + + 21 22 6 O2 6 H2O 6 O2 6 H2O Number of ENTROPY Change in ENTROPY Change in ENTROPY Change in ENTROPY Change in Possible States ∆ Freedom ∆ Freedom ∆S Low entropy ∆S That can be Number of Few Many Present in States possible states States Few Many Roll of “2” “Dispersed” that can be States States Only 1 possible “Dispersed” present in: “state” Roll of “7” time + - 6 possible NaCl Na Cl NaCl Na+ Cl- High entropy “states” crystal ions in water crystal ions in water 23 +∆S 24 Change in Energy that Energy that The Free Energy Change Chemical Goes to Goes to Bond Do Useful Work ∆ Randomness Do Useful Work G Energy Dictates whether a reaction will Dependent On Proceed spontaneously or not Enthalpy EntropyOn “free energy” Temperature (Gibb’s Free Energy) Kinetic Movement Whether a Reaction is ∆H = T∆S + ∆G Favorable or Unfavorable ∆G = ∆H - T∆S If ∆G = negative # “spontaneous” 25 reaction is energetically favorable 26 An exergonic reaction – Proceeds with a net release of free energy and is spontaneous “will happen” Reactants Amount of energy released (∆G <0) Energy Free energy Products ∆G = ∆H – T∆S - ∆G is favorable exergonic “spontaneous” Progress of the reaction + ∆G is NOT favorable, endergonic, nonspontaneous27 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 change in Entropy “doesn’t happen” Reduced Complex Products Amount of energy released Oxidized Simple (∆G>0) Energy Free energy Reactants The sum of these is the Net Useful Energy (∆G) Progress of the reaction If ENERGY RELEASED - EXERGONIC = FAVORABLE Figure 8.6 (b) Endergonic reaction: energy required net 29 If require net ENERGY INPUT - ENDERGONIC = UNFAVORABL30 E Complex Simple change in Entropy High Reduced (no oxygens) EXERGONIC REACTIONS gasoline burns H HHHH HHH Lower iron rusts H-C-C-C-C-C-C-C-C-H H hydrogen and oxygen form water (explosive!) HHHH H HH H 8 H-C-H hydrocarbon fats H H R-C-OH H Either: go to bonding arrangement with lower potential energy alcohol O = Bond Energy sugars R-C-H Or: go from a more complex state to a simpler state aldehyde O = Final R-C-OH product 1 molecule of 8 carbons vs 8 molecules of 1 carbon change in acid O=C=O Carbon31 dioxide 32 Low Oxidized Lowest ∆H = Hproducts -Hreactants ∆H= - favorable ∆S= + favorable − ∆H ∆G= very - favorable exothermic Heat released + ∆H 2 endothermic Heat input Spontaneous Favorable - it can happen33 icepack 34 ∆H= + Unfavorable ∆H= - very favorable ∆S= + Very favorable ∆S= - unfavorable ∆G= - favorable ∆G= - favorable Entropy Driven Reaction Enthalpy Driven Reaction Spontaneous Spontaneous Favorable - it can happen Favorable - it can happen 35 36 Entropy overwhelms Enthalpy Enthalpy overweighs Entropy ∆H= + unfavorable ∆S= - unfavorable ∆G= + unfavorable ∆G = ∆H – T∆S ∆G = ∆H – T∆S ∆G = ∆H – T∆S - (-) - (+) - (-) - (-) - (+) - (+) Non-spontaneous Spontaneous Enthalpically Entropically Non-spontaneous 37 NOT Favorable - it can NOT happen38 Favorable Rxn Driven Rxn Driven Rxn NOT Favorable - it can NOT happen Tie a favorable rxn with A typical COUPLED Reactions Tie a favorable rxn with An otherwise unfavorable rxn ENDERGONIC/Unfavorable/NonSpontaneous REACTION An otherwise unfavorable rxn - building a polymer Monomer + Monomer 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 Drive otherwise unfavorable an exergonic reaction with an endergonic reaction 39 reactions40 1. ∆G = +5.5 kcal/mole 2. ATP+ H2O ADP + Pi ATP ∆G = -7.3 kcal/mole Note: ∆G = -7.3 kcal/mole ADP + Pi Each step is favorable +∆G = +5.5 kcal/mole Favorable or unfavorable41 ? Net rxn ∆G = -1.8 kcal/mole42 Coupled Reaction Another Example of a Coupled Reaction ADP -P + monomer1 ADP-monomer1 + P (ATP) I’m free! Endergonic reaction: ∆G is positive, reaction is not spontaneous ∆G = -1.0 ADP-monomer1 + monomer 2 NH2 Now tied together NH Glu + 3 Glu ∆G = +3.4 kcal/mol Glutamic Ammonia Glutamine ADP + monomer1-monomer 2 acid Now I’m free too! Exergonic reaction: ∆ G is negative, reaction ∆G = -0.8 is spontaneous 7.3 units released + P ∆G = + 7.3 kcal/mol ATP + H2O ADP Net: ATP +H2O ADP + P monomer1 + monomer2 monomer1-monomer2 + H O 5.5 units needed 2 Coupled reactions: Overall ∆G is negative; Figure 8.10 together, reactions are spontaneous ∆G = –3.9 kcal/mol DO NOT LET ATP FALL APART IN 1 STEP, 43 44 use energy in its bond to MAKE the polymer linkage Three types of cellular work powered by ATP hydrolysis Equilibrium P i Physical P Reactions in a closed system movement – Eventually reach equilibrium Motor protein Protein moved Driving (a) Mechanical work: ATP phosphorylates motor proteins Conformational Membrane Changes ∆G < 0 ∆G = 0 protein ADP ATP + Of Active P Proteinsi PP Transport i Pumps Solute Solute transported (b) Transport work: ATP phosphorylates transport proteins P NH2 + NH + P Glu 3 i (a) A closed hydroelectric system. Water flowing downhill turns a turbine Glu Biosynthetic that drives a generator providing electricity to a light bulb, but only until the system reaches equilibrium. Figure 8.7 A Reactants: Glutamic acid Product (glutamine) Coupled and ammonia made Rxn45 46 Figure 8.11 (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 (c) A multistep open hydroelectric system. Cellular respiration is analogous to this system: Glucoce is brocken down in a series Figure 8.7 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. 47 48 For example, oxidation of glucose: Summary: 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 -biological systems always need 49 constant energy input 50.