14 27 Sept 2010

14 27 Sept 2010 - David L. Nelson and Michael M. Cox...

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LEHNINGER PRINCIPLES OF BIOCHEMISTRY Fifth Edition David L. Nelson and Michael M. Cox © 2008 W. H. Freeman and Company CHAPTER 6 Enzymes
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Chemical reactions Chemical reactions have barriers – activation energy In uncatalyzed reactions, energy is obtained through collisions Collision frequency increases with temperature The efficiency of the reaction depends on the orientation of molecular orbitals In catalyzed reactions, the orientation of reacting molecules is less random The molecule adsorbed to the catalyst may also have different energetics No longer entirely dependent on random collisions The direction of the reaction (i.e. states) remain unchanged – lower potential energy and higher entropy
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Pasteur noted that yeast convert sugar to ethanol He concluded that living yeast are vital to catalysis Buchner proved yeast extracts still have catalytic activity Kuhne proposed the name “enzymes” – the molecular catalysts Sumner isolated jack bean urease, a protein with catalytic activity, and proposed that all enzymes were proteins Haldane proposed that substrates have weak interactions with enzymes based on mathematical analysis
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Most enzymes are protein – a few “ribozymes” have been discovered Names usually ends with -ase The enzyme must remain intact to retain catalytic activity Two types of enzymes - catalyze the reaction using amino acids side chains - catalyze the reaction using cofactors (vitamins and minerals) Organic cofactors are sometimes called “coenzymes” Cofactors that remain bound to the enzymes during catalysis are called “prosthetic groups” Some cofactors exchange after each reaction
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This note was uploaded on 09/18/2011 for the course CHEM 3510 taught by Professor Mueser during the Spring '10 term at Toledo.

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14 27 Sept 2010 - David L. Nelson and Michael M. Cox...

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