BioNotes3 - Notes 7, 8 Monday, September 24, 2007 1:01 PM...

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Notes §7, 8 Monday, September 24, 2007 1:01 PM 1. 2. Metabolism o Sum total of all chemical reactions that occur within an organism o Also referred to specific chemical reactions at the cellular level o o Sunlight: ultimate source of energy (radiant energy) o Photosynthetic organisms convert radiant energy (sunlight) to chemical energy o Living organisms convert chemical energy into structure & also different types of chemical energy 4. Chemical reactions o 2 factors govern fate of a chemical reaction: Direction Many cells use ATP to drive reactions in 1 direction Rate Catalysts called enzymes can speed the reaction rate 5. Energy o Ability to promote change/do work o 2 forms Kinetic movement Potential Due to structure or location Chemical energy - energy in molecular bonds o Figure 7.1 6. 2 laws of thermodynamics o First law: conservation of energy Energy can't be created nor destroyed o Second law: Transformation of energy from one form to another increases entropy (degree of disorder/randomness of a system) o Figure 7.2 (also see notebook) 7. Free energy o Energy available for work Energy transformations involve an increase in entropy Entropy - a measure of the disorder that can't be harnessed to do work H = G +TS H = enthalpy or total energy G = free energy or amount of energy for work S = entropy or unusable energy T = absolute temperature in Kelvin (hotter something is, more energy you have)
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ΔG = ΔH - TΔS Exergonic o ΔG < 0 or negative free energy change o Spontaneous Endergonic o ΔG > 0 or positive free energy change o Requires addition of free energy o Not spontaneous 8. Spontaneity: clarification o Spontaneous reactions do NOT just go forward immediately to produce products o This is b/c the reactants must overcome an activation energy, E A . 9. Figure 7.3 o Hydrolysis of ATP o ΔG = -7.3 kcal/mol o Reaction favors formation of products o Energy liberated can drive a variety of cellular processes. 10. Cells us ATP hydrolysis o An endergonic reaction can be coupled to an exergonic reaction o Endergonic reaction will be spontaneous if _____ _____ energy change for both processes is negative ------- Glucose + phosphate ---> glucose-phosphate + H2O ΔG = +3.3 kcal/mol Endergonic ATP + H2O ---> ADP + Pi ΔG = -7.3 kcal/mol Exergonic Coupled reaction: Glucose + ATP ---> glucose-phosphate + ADP ΔG = -4.0 kcal/mol Exergonic 11. Enzymes o A spontaneous (exergonic) reaction is not necessarily a fast reaction o Catalyst - Agent that speeds up the rate of a chemical reaction without being consumed during the reaction o Enzymes - Protein catalysts in living cells 12. Activation energy o Initial input of energy to start reaction o Allows molecules to get close enough to cause bond rearrangement o Can now achieve transition state when bonds are stretched 13. Lowering activation energy
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This note was uploaded on 04/12/2008 for the course BIO 240 taught by Professor Evans during the Fall '08 term at Hope.

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BioNotes3 - Notes 7, 8 Monday, September 24, 2007 1:01 PM...

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