LECTURE 13-27 - Reactions and Enzymes 24/10/2008 08:21:00...

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Unformatted text preview: Reactions and Enzymes 24/10/2008 08:21:00 Energy and Life Autotroph: producers, can fix inorganic carbon Heterotroph: consumers Energy: capacity to do useful work Six Uses of Energy by Organisms Muscular work Produces Heat as byproduct Concentration compounds concentration gradient across membrane Electrical work Synthesis, growth Bioluminescent work Thermodynamic Laws 1 st law conservation of energy the total amount of energy in the universe remains the same. Energy can neither be created or destroyed. It is just trasformed 2 nd law entropy happens the entropy of a system not at equilibrium will tend to increase over time. Every energy transfer or transformation increases the entropy of the universe thus, even if a given system becomes more ordered, the universe becomes more disordered Gibbs free energy G, joule G = H-TS H= enthalpy, total energy of a system, a measure of the type and quantity of the chemical structure (joule) S= entropy, a measure of the disorder of the system (joule/K) T= temp (Kelvin) For a reaction: G = G products G reactions G = H-T S ex: people jumping off platform. High potential energy on top. G is neg because they go from high to low energy state. Closed system: reactions process for while until the buildup of products. Then stable equilibrium is reached. o Reaction at start (water wheelstarts with higher free energy) and then reaches equilibrium and G = 0 o Biological systems are not closed always taking in energy from the environment Open system: products may be removed as they are formed. Does not reach equilibrium and continues in the forward direction as long as there are enough reactants available Cellular reactions rarely at equil, products are removed as rapidly as they are formed Multi step reaction may proceed even if they are endergonic (require energy), if coupled to an exergonic (releases energy) step Nevertheless, most biological reactions are endergonic Exergonic reactions G<0 releases energy endergonic reactions G>0 need energy (reactants have low free energy and products have more free energy)products are more organized because higher level of free energy glycolysis o breakdown of glucose is exergonic o G = -2870 KJ/mole o energy is released glycogenesis o making glucose is endergonic o co2 + h20 glucose and o2 o G = +2870 kj/mole o energy must be put it energy for coupled reactions comes from hydrolysis of adenosine triphosphate, ATP o add water, phosphate is split off and you get ADP + energy o regeneration of ATP by condensation o 10 million molecules of ATP per second per muscle cell Activation energy Required activation energy Ea prevents reactions from running downhill Uphill reaction for a reaction to happen first from free energy at the start to the transition state = activation energy...
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This note was uploaded on 10/31/2008 for the course BIO G 1101 taught by Professor Gilbert during the Fall '07 term at Cornell University (Engineering School).

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LECTURE 13-27 - Reactions and Enzymes 24/10/2008 08:21:00...

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