1. catalysis: the process by which a catalyst changes the
rate and mechanism of a chemical reaction
-- a catalyst is…
NOT consumed during
the course of a reaction
-- Catalyzed and
uncatalyzed
reactions have...
completely different mechanisms.
This is WHY catalyzed and
uncatalyzed reactions have
different activation energies.

2. Homogeneous catalysts are present in the same
phase as the reacting molecules.
Heterogeneous catalysts exist in a different phase
than the reacting molecules. --
usually solid catalysts in gaseous
mixtures or liquid solutions
Catalytic
converters
often use Pt as a
catalyst to help turn
CO into CO2, NxOx
into N2 and O2, and unburned
hydrocarbons into CO2 and H2O.
Research on catalysts is one of
the most important areas of
modern science.

3. The first step in heterogeneous catalysis is _________
of the reactant molecules onto the metal surface –
specifically, onto the _________, which are the
locations at which reactants attach to the metal catalyst.
adsorption
active sites --
R bonds are broken or weakened,
allowing P to form w/a lower Ea
-- then, the products detach
from the catalyst
enzymes:
biological catalysts
-- large protein molecules
(104 – 106 amu)
-- usually very specific
 for only one reaction
-- names end in... “____”
-ase
-- substrates: substances (i.e., reactants) that
react at the active sites of enzymes

4. -- The lock-and-key model explains how an enzyme
affects a substrate molecule and changes it into a
new substance.
substrate (i.e., reactant)
Lock-and-Key
Model
active
site
enzyme-substrate
complex
products
enzyme
active
site is ready for
more substrate

5. turnover number:
~103 – 107 per sec.
Enzyme inhibitors bind to the active
site or alter the unique shape of an
enzyme molecule, destroying
the enzyme’s activity.
e.g.,
poisons,
Pb,
Hg,
others