Enzymes
• Large molecules made of various amino
acids
• Act as catalysts to speed up reactions w/out
being destroyed
– Highly specific
– Lowers energy of activation level
Enzymes lower
the energy of
activation for a
reaction
Enzyme Kinetics
E + S ES complex E + P
• Effect of substrate concentration
– 10 test tubes of fixed [E]
– Add gradations of [S]
– Measure rate of reactions
• Vmax occurs when
enzyme active sites
are saturated with
substrate
• Km (Michaelis-
Menten constant)
reflects affinity of
enzyme for its
substrate
• smaller the Km, the
greater the affinity an
enzyme has for its
substrate
Enzyme Kinetics
• [S] generally B ------> C ------> D
initial substrate final substrate
First step is usually irreversible
and controlled by an allosteric enzyme