Transcript Enzymes Lab 5 Enzymes • Reaction characteristics – Enzymes are catalysts: substances that speed up or facilitate a chemical reaction by LOWERING the activation energy –

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
Requires energy
Exergonic Reaction
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. Temperature
2. 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.