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1/26/11 Thermodynamics A. Physiochemical Processes and Life 1. Life evolved from spontaneous physiochemical processes. 2. Thermodynamics – the study of the conversion of energy within matter. 3. System – the region of experimental interest. Ex: engine, reaction vessel, organism. a. Closed system – energy and matter is totally recycled, no energy escapes to surroundings. b. Open system – interacts with surroundings. 4. Surroundings – the rest of the universe. 5. Organisms are open systems. a. Use high quality free energy for life’s processes. b. Release low quality free energy – heat. c. Maintain order at cost of increased universal disorder. **All three are necessary for life, cant have only two. B. Enthalpy 1. The total energy of a system (H). Ex: a snail or a banana is a system. 2. Kinds of energy a. Chemical bond energy b. Phase (gas, liquid, solid) c. Concentration (low to high) – changes in concentration changes the total energy of the system. d. Order (random to organized) 3. Change in enthalpy = ∆H ∆H = Hfinal – Hinitial C. Free Energy and Entropy 1. Gibb’s free energy (G) – what portion of the total energy is available to do work. 2. Entropy – measure of disorder in a system (S), degree of randomness. a. Correlated with heat content. b. Entropy always wins – in a system, the moment you stop maintaining internal structure you die. 3. Available energy ∆G = ∆H - T∆S a. ∆G = change in Gibb’s free energy – change in energy available to do work b. ∆H = change in total energy c. T = absolute temperature in oK d. ∆S = change in entropy D. 1st Law of Thermodynamics1. Energy is neither created nor destroyed - involves system and surroundings. a. ∆H = 0 b. Energy can be transformed into another form. Photosynthesis electromagnetic E (light) → chemical E (organic compounds) + heat E Cellular Respiration chemical E (organic compounds) → chemical E (ATP) + heat E c. Energy is transformed from one form to another during these processes. d. Any energy not used is given off as heat to the environment. e. Photosynthesis and cellular respiration are not reverse reactions of each other. They both give off heat as an end product. 2. Life’s challenge – transform available energy into useful forms at the right places and at the right times. a. Ex: a cheetah does work because it applies force to the ground to move the body over a certain distance. b. Needs to transport energy in precise place and a precise amount. 3. 1st Law describes energy and how it’s balanced on both sides of the equation. E. 2nd Law of Thermodynamics ∆G = -T∆S (2nd law) 1. Determines directionality in a reaction. 2. All processes proceed in the direction that reduces the free energy available to do work. **∆G < 0 or ∆S > 0Examples Spontaneous processes - -going down a slide . delta g changes -more organized systems to less organized systems – increases the entropy Spontaneous Processes (∆S > 0) ␣ Heat – increased random molecular Movement, heat has the highest entropy u can get. ␣ Lowest quality of useful energy (high S) Photosynthesis: light E → chemical E + heat E Respiration: cchemical E → chemical E + heat E *direction these processes occur sponaneuously -move in a direction that decreases the amount of free energy – why they are spontaneous -increase the randomness in the system -entropy in these two reactions is heat. -organisms evolve using spontaneous reactions kinetics – reaction rates -about the rate of reaction -exert control over spontaeneous reaction -all reactions have an activation energy -activation energy is the necessary energy to start a reaction Ea -a lot of energy makes bonds unstable and causes the reaction to occur -all chemical reactions have an activation energy. Kinetics and catalysts -catalysts lower the activation energy -3 kinds – 1. Inorganic, metallic ions 2. Enzymes with metallic ion cofactors 3. Enzymes without cofactors -most ancient enzymes in organisms have metallic ions. More recent evolutions do not. Examples -chlorphyll a – photosynthesis !most&primative&enzyes&all&have&metallic&ion&cofactors&!when&life&evolved&it&1.&Usd&spontaneous&reactions&2.&Metallic&ion&catalysts&&!over&time&organisms&found&out&how&to&do&that&without&the&metal&ions.&&&Life’s Evolutionary Scenario • Earliest life – used physicochemical processes to carry out the functions oflife. Used spontaneous reactions and metal ions to catalyze those reactions.


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UMD BSCI 207 - Thermodynamics

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