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Biology 1002 Energy and Enzymes.pdf

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Biology 1002B
Tom Haffie

Lecture 4: Energy and Enzymes January 17, 2013 • 2nd law- disorder of system +surroundings increases • life is ordered • cell is an open system • living things is ordered but it gives off heat and motion which increases the disorder of the universe • you need to eat to maintain low entropy Free Energy ∆G = ∆H -T∆S • delta G= free energy • delta H= enthalpy (endothermic reaction+, exothermic reaction-) • delta S= entropy (more or less disorder) • Exergonic and Endergonic • Exergonic reactions are those that release energy. During these reaction the reactant has higher free energy than the product. This is expressed by -G (negative Gibbs number). These reaction occurs spontaneously and their rate is usually increased by enzymes. • Endergonic reactions are those that store energy. During these reactions the reactant has lower free energy than the product. This is expressed by +G (positive Gibbs number). • Spontaneous reactions are exergonic ...-delta G (delta H also negative) • tends to be spontaneous when the products have less potential energy then the reactions Contributions of Enthalpy and Entropy • solids are more ordered than a liquid or a gas • ice melting is an entropy driven process (massive increase in entropy)... delta H is actually positive Enzymes • enzymes catalyze something 10 ^12-10^20 faster Why does life need enzymes? speed • • low temperature (to overcome that living cells cannot handle high temperature so the enzymes keep the temperature low and the reaction fast) Lecture 4: Energy and Enzymes January 17, 2013 What enzymes do and don’t do • enzymes cannot make a non-spontaneous reaction spontaneous cannot convert a reaction with a positive delta G to a negative delta G • • the only way to get a non-spontaneous reaction go is energy and then enzymes are usually used Exergonic Reaction Energy Profile first bar(from top):Transition state second: Ea third: delta G
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