Lecture 21-Enzymes

Lecture 21-Enzymes - Lecture 21- Enzymes Enzymes speed up...

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Lecture 21- Enzymes Enzymes speed up biological reactions by 108 to 1020 times. For example: the dephosphorylation of glucose. Without an enzyme, it would take 1 trillion years. Exergonic Reaction - The rate of reaction is proportional to the number of molecules you can get to the transition state. (Lots of molecules in the transition state will give a fast reaction; a few will give a slow reaction.) Activation Energy - How much energy is required to get to the transition state (limits the rate of reaction; a kinetic barrier) - An example of that kinetic barrier: Propane is thermodynamically unstable, but kinetically stable because the molecules need activation energy. - Enzymes lower the activation energy of a reaction, but do not affect ΔG. Why do we need enzymes? Biological processes occur at temperatures too cold for reactions to occur- organisms just aren’t warm enough. Enzymes lower the amount of energy (heat) necessary for a reaction to take place. Enzyme Structure - Proteins - Structure based on tertiary and quaternary structure - Folding is called conformation (the enzyme must acquire the correct shape) - The enzyme can change conformation to fit the substrate; not a “lock and key”: induced fit - Active site: where the reaction takes place - Small 3D cleft - Can only find it after we see reaction take place (primary sequence cannot deduce where
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This note was uploaded on 04/04/2009 for the course BIOLOGY 1222 taught by Professor Haffie during the Spring '09 term at UWO.

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Lecture 21-Enzymes - Lecture 21- Enzymes Enzymes speed up...

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