Post on 31-Oct-2014
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Enzymes & Chemical Reactions
What is Energy???
LAWSFirst Law of Thermodynamics –
Energy is not created nor destroyed, just changed from one form to another
Second Law of Thermodynamics- Entropy always increases in a closed system. ie. Physical & chemical processes proceed in the direction that results in lower potential energy & increased disorder.
Free Energy ∆G - Change in free energy
Exergonic – Release of free energy. Spontaneous reactions and ∆G is less than zero.
Endergonic – Require input on energy. Non spontaneous and ∆G is greater than zero.
Enzymes & Catalysis
Transition state
Reactants
Products
Activation energy
Reactants
Products
Transition state
Ea with enzyme
∆G does not change
Induced Fit
Enzyme Substrate
Figure 3-22
A MODEL OF ENZYME ACTION
Substrates
Enzyme
Transition state
Shape changes
Products
1. Initiation: Reactants bind to the active site in a specific orientation, forming an enzyme-substrate complex.
2. Transition state facilitation: Interactions between enzyme and substrate lower the activation energy required.
3. Termination: Products have lower affinity for active site and are released. Enzyme is unchanged after the reaction.
Competitive Inhibition
Enzyme Substrate
Allosteric Regulation
Enzyme Substrate
Figure 3-25a
Enzymes from different organisms may function bestat different temperatures.
Glucose-6-phosphatase from bacterium that lives inside humans
Glucose-6-phosphatase from bacterium that lives in hot springs
Figure 3-25b
Enzymes from different organisms may function bestat different pHs.
Chitinase from bacterium that lives in acidic pools
Chitinase from soil-dwelling bacterium