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Biology 1002B
Tom Haffie

Lecture 4 1. meaning of potential, kinetic, chemical energy, closed, open vs. isolated systems, First Law of Thermodynamics, Second Law of Thermodynamics, entropy, spontaneous reaction, enthalpy (H), DH, exothermic, endothermic, Gibbs Free Energy, exergonic, endergonic, DG, catalyst, rate of reaction, energy of activation (E A, transition state, kinetic stability, active site, catalytic cycle t. Energy of activation: Every reaction requires a certain minimum energy for the reaction to occur--it is called a u. Transition state: the transitory of molecular structure in which the molecule is no longer a substrate but not yet a product. v. Catalytic cycle: enzyme:substrate binding -> enzyme+ product. And Enzyme is recycled and interact with another substrate. 2. Why life does not go against the second law. Life does not go against the second law. Life is highly order (ex. cells) The cell is open system. It allows energy to exchange. We maintain low level of disorder(entropy) by taking in energy (eating) and the consequences is the heat. And heat produced increases the disorder. Living things increase disorder of the surrounding. 3. Why life needs to consume energy? Life needs to consume energy (ATP) to maintain low level of entropy. 4. Components of Gibbs Free Energy equation The energy available to do work. Delta G=delta H – T delta S. ex. Breaking down of the protein, glucose, melting of ice etc. Free energy depends on enthalpy and entropy. Enthalpy : endothermic (+) and exothermic (-) Entropy: more disorder (+) and less disorder (+) Free energy: endergonic (+) and exergonic (-) 5. Whether or not a given reaction will be spontaneous, given deltaG spontaneous reactions are reactions that can take place without energy input. Reactions tend to be spontaneous-the reaction is exergonic (delta G is -) when a. Enthalpy is exothermic when product has less potential energy than the reactant. ex. Glucose is more potential energy than the products. b. Entropy is higher in the product than in the reactant. Product is more disorder than the reactant. Whenever the system undergoes a phase change (solid to liguid and gas), the entropy increases. Gas is more disorder than liquid and solid. c. Endothermic, but really high entropy causes negative delta G (entropy driven) 6. Role of enzymes in endergonic vs. exergonic reactions Uncatalyzed OMP decarboxylation has a half time of 78 million years, while OMP-enzyme decarboxylation has a half-time of 20 millisecond. They are both spontaneous reaction. a. Enzymes can increase the rate of the spontaneous (exergonic) as long as it is spontaneous 10^12 – 10^20 times. b. Enzyme cannot help the conversion of reactant to product if they are endergonic reaction (+ delta G) – this reaction would require energy in order to proceed and enzyme cannot provide energy for a reaction, not change the sign of + delta G of a reaction. To change this sign, energy (ATP) is required ex. light. 7. Relationship between activation energy and rate of reaction. The reason why some spontaneous reaction goes slowly: activation energy. This represents a barrier that needs to overcome, after overcoming this barrier it can th
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