Youtor
Enzymes I
>> YOUR LINK HERE: ___ http://youtube.com/watch?v=TwX_YGCSDX8
This course is part of a series taught by Kevin Ahern at Oregon State University on General Biochemistry. For more information about online courses go to http://ecampus.oregonstate.edu/ • Playlist • Also check out the free textbook Biochemistry Free and Easy at: http://biochem.science.oregonstate.edu • 1. Enzymes are proteins that catalyze reactions. • 2. Enzymes are capable of speeding reactions quadrillions of times faster than the same reactions would occur in the absence of enzymes. • 3. Non-proteinaceous molecules that bind to enzymes and help the enzymes to catalyze reactions are called coenzymes. • 4. The Gibbs free energy is the energy available to do useful work in reactions. The change in the Gibbs free energy for a reaction is important because it determines whether a reaction is favored, unfavored, or at equilibrium. • 5. Thus, when the Gibbs free energy change is negative, the reaction in question goes forward as written, but when the Gibbs free energy change is positive, the reaction goes in reverse. • 6. A related term to G is G°', which is the Standard Gibbs Free Energy change. This refers to the Gibbs Free Energy change for a reaction under standard conditions. Since most reactions occur at non-standard conditions, G is much more useful than G°'. In fact, the sign of G°' does NOT tell the direction of a reaction, except under standard conditions. • 7. Chemical reactions require activation energy (I'll call it G+ here) in order to get started. Catalysts (both enzymes and non-biological catalysts) act by lowering G+. Catalysts DO NOT CHANGE G. All they do is lower the energy required to activate the reaction. While enzymes speed reactions immensely, they therefore DO NOT CHANGE THE OVERALL REACTION CONCENTRATION AT EQUILIBRIUM. They simply allow the reaction to get to equilibrium faster.
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