AP Biology/LABORATORY 2. Enzyme Catalysis

Enzymes are responsible for speeding up the rate of a reaction, but not changing whether or not a reaction is favorable. Enzymes act to reduce the activation energy of a reaction by increasing the local concentration of the reactant putting the reactants in the proper conformation straining the reactants to favor the transition state Enzymes have an active site where the reactants bind and may have additional sites affecting their activity. Enzymes' level of activity is affected by the presence of substrate and can eventually reach a maximum if all active sites are saturated. Enzymes aren’t living, so they can’t “die”, but under certain conditions (e.g., extreme temperatures, pH changes, exposure to certain chemicals) they can become denatured. When enzymes denature, their active sites (where substrates bind) change shape, rendering them less effective or completely inactive. Often, once denatured, enzymes cannot catalyze reactions as they normally would, because their structure is essential to their function. thumb|400px|Diagram showing the “lock and key model” via an induced fit diagram.