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.