An Energy Diagram of a Reaction: 
a Plot of State Versus Energy
•	A plot of the free energy of the reaction vs the course of the reaction:
Spontaneous: Clarification
•	Spontaneous reactions do NOT just go forward immediately to produce products.  
•	This is because the reactants must overcome an activation energy, EA.

•	Enzymes are protein catalysts that enormously speed up reactions.  They often have an “-ase” ending to their name.
•	e.g.,  hexokinase, catalase, peptidase, mutase
•	They are not themselves changed (except for a brief period of time) and are the same before and after a reaction.
•	Enzymes:
•	Lower the activation energy: this is the MOST important characteristic
•	Do not add or remove energy from a reaction
•	Do not change the equilibrium for a reaction
•	Are reused over and over

Enzyme Function