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Unformatted text preview: Bio 1A.Feb. 4,2009 Lecture 7. Wilt Thermodynamics, Enzymes, and Co-Factors I. Free energy and reaction rates A. Recall that living organisms are systems that use reduced carbon for energy, which is obtained by oxidation, and also use carbon for the molecular skeletons of biosynthesis. B. Such chemical transformations involve many reactions. This whole constellation of reactions is called metabolism . C. The reactions themselves may consume or relase energy because rearrangement of atoms and bonds in a reaction involves energy. D. Review of thermodynamics 1. First law: energy cannot be created or destroyed , just transferred or transformed 2. Second law : every energy transformation or transfer leads to greater entropy in the universe. (One measure of entropy is the degree or disorder; greater entropy is greater disorder. a. or,put another way, energy transformations flow "down hill". b. this doesn't mean that you can't have transformations that result in more order (less entropy), but it does mean that somewhere else in the universe there is a corresponding increase in entropy. Energy requiring transformation need an input of energy from the "outside". 3. Of the energy present in a given state, only some is available to do work (chemical, electrical, mechanical). That energy is " free energy ", called G . Organisms live at the expense of free energy that they get from the environment ( heat, light, reduced carbon). 4. The relationship between free energy, total energy and entropy is: G=H-TS, where T is the temperature in Kelvin, G is free energy, H (enthalpy) is total energy, and S entropy. In any change in energy accompanying a chemical reaction, entropy....
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- Spring '08