BIOL 215 Lecture Notes - Part 3A

BIOL 215 Lecture Notes - Part 3A - Bioenergenics WW The...

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Unformatted text preview: ' Bioenergenics WW - The Thermodynamics of Biological Systems System Open or closed object ofinterest. Living systems are open systems that can exchange energy with their surroundings. Universe The system and its surroundings. Eouiiiurium Volume. pressure_. temperature. and the concentrations ofthe contents contained within are ail constant. In biologicai systems. volume. pressure. and temperature are generain constant. Internai The totai energy ofa system at a given state. energy {E} Absolute internal energy cannot be measured, but a change in internal energy ME) can be caiculated. Entnaisy {H} A measure of internal heat. Generally more useful than E; H : E + P‘J: :1‘.H : :1‘.E + Pay + yap: :1‘.H : i..E because pressure and volume do not change in a biological system. Caiorie The amount of energy required to raise one gram ofwater one degree (cal) centigrade (from 14.5 to 155°C) at normal atmospheric pressure: nutritional caiories are kilocalories {kcal}. 1st {am of Thermodynamics Energy can neither be created nor destroyed. If {E = E: — E1. at = gum . i —gtg..;.u;iore.H = Hp — Hr. Endotnermic Hp > Hr: energy is absorbed in the reaction. Exotnermic Hp < H: energy is emitted in the reaction. Spontaneous reaction A reaction that occurs without any input of energy. 2nd Law of The universe is moving tow'ard an increasmg degree of Thermodynamics randomness. or entropy. Entropy A measure of disorder. (S) (3.5 alone is not enough to determine the directionality of a reaction (ex: a beaker of water Freezes spontaneously: even though ice is more ordered than liquid water}. Eouiiibrium constant Q at equilibrium. fig“;- Must be know in order to determine the directionality of a reaction. Reaction quotient (Q) 'For a reaction 3353. + pg —) 5g + gig. Q _ [producis] _ [C]: [D]3 _ reacmnm _ [A]°[B]= When Q < m. the reaction will move to create more products. when Q > g“. the reaction will move to create more reactants. Gibbs free energy AG‘ = M{Q_illggg) (G) This is the amount of energy that is released when a reaction moves from Q to is“. when so < CI. the reaction will occur spontaneously. when AG' > 0. the reaction will not occur spontaneously. Standard state free aGD' = EW{§§Q} ei1ergy(t‘.G°') This is the so when the reaction components are in the standard state. or one molar each and Q = 1. Ceiiuiar In a biological system. pH [H2O] = 55M and any quantitative changes are negligible due to the greatness ofthe excess of water. [H'] = l X 10"1 {because celi pH is 7} and any quantitative changes are negligible due to pH buffering in the cell. ...
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This note was uploaded on 04/14/2008 for the course BIOL 215 taught by Professor Diiulio during the Fall '07 term at Case Western.

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BIOL 215 Lecture Notes - Part 3A - Bioenergenics WW The...

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