MICRB 265 (09/25/13) Bioenergetics: Part 1 - Energetics and Enzymes

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Microbiology (Biological Sciences)
Brian Lanoil

MICRB 265 (September 26, 2013) BIOENERGETICS (Part 1): Energetics and Enzymes  First Law of Thermodynamics o Energy cannot be created nor destroyed  It can only be transferred from one state to another o kJ is the most useful unit for explaining energy instead of kCal, which only measures heat  Second Law of Thermodynamics o There is always going to be a loss of energy (entropy) in a system after a reaction takes place o No such thing as 100% yield for one type of energy o Reactions are either endergonic (requiring energy) or exergonic (giving off energy) Redox Coupled Reactions Oxidezed – loss of electrons Reduced – gain of elections LEO says GER  Oxidized molecules have lost electrons therefore they are now electron acceptors  Reduced molecules have gained electrons therefore they are no electron donators  ΔG = change in free energy (Gibbs free energy) o Units in kJ o Super script “ 0’ ” means “under standard conditions” 0’  Ex. ΔG = change in free energy under standard conditions  25 degrees Celcius  Neutral pH  1M conc. o Negative value = energy given off by system o Positive value = energy taken by the system from the surroundings Stepwise Oxidation of Methane  Stepwise conversion (“conservation of energy”) allows for the segmented energy yields from fuel in biological organisms.  In chemistry, methane reacted with O would result in a combustion reaction. 2 o If this happened in an organism, the organism would die from the sheer amount of energy being released… therefore they have a different method of energy harvesting (stepwise conversion)  The overall energy yield of stepwise conversion is the same as simple combustion but it separated into small manageable burst of energy 0  G = G + RTlnK o K = [products]/[reactants]  K > 1  reaction favours reactants  K < 1  reaction favours products  K = 1  reaction has reached equilibrium What Happens if H a2d O are2Mixed Together?  Nothing… UNLESS there is a catalyst Direction of Electron Transfer  Exergonic Reactions o Electrons transferred from molecules with more negative E potent0als to molecules with more positive E po0entials. o Aka catabolic (or energy deriving) reactions  Endergonic Reactions - o e from m
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