Enzymes

1. Enzymes Lab 5

2. Enzymes • Reaction characteristics • Enzymes are catalysts: substances that speed up or facilitate a chemical reaction by LOWERING the activation energy • Energy of Activation: Amount of energy needed to start a reaction

3. Activation Energy Endergonic Reaction Exergonic Reaction Requires energy Releases energy

4. Ways to Lower the Energy of Activation • Enzymes • Protein catalysts that lower the amount of energy needed to get the chemical reaction going • They maintain their original chemical composition while causing a change in the substrate (reactant) • The specific shape of the enzyme allows it to catalyze only one reaction • Active site = place on the enzyme that binds substrate • Since the enzyme does NOT change its shape, it is REUSABLE

8. Altering the Rate of an Enzymatic Reaction 1. Temperature 2. pH

9. Altering Temperature • Gradual ↑ in temperature will INCREASE the rate of the reaction • How? By an increase in the speed at which the molecules are moving • This results in increased collisions of the enzyme and substrate • Extremely low temperatures will SLOW DOWN or STOP the reaction • Why? The enzyme and substrate are moving too slow to collide • Extremely high temperatures will STOP the reaction • Why? Because the enzyme will be denatured!

10. Altering pH • Alterations in pH will STOP the reaction because the enzyme will be denatured! • Remember, a small pH change does NOT correlate with a small change in the pH of the environment!! • Why? pH scale is logarithmic

12. Enzyme Questions • The presence of an enzyme _____ the required energy of activation of a chemical reaction. • Generally, as the amount of substrate is increased, the rate of the reaction _____. • Raising the temperature to over 50C ___ the rate of an enzymatic reaction. • Lowering the pH for an enzyme that works best in a highly acidic environment ___ the rate for the reaction.