enzymes lab 5. enzymes reaction characteristics – enzymes are catalysts: substances that speed up...
TRANSCRIPT
Enzymes
Lab 5
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
Activation Energy
Endergonic Reaction Exergonic ReactionRequires energy Releases energy
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
Altering the Rate of an Enzymatic Reaction
1. Temperature2. pH
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!
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
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.