Introduction - Enzyme Characteristics:
The basic mechanism by which enzymes catalyze chemical reactions
begins with the binding of the substrate (or substrates)
to the active site on the enzyme. The active site is the
specific region of the enzyme which combines with the substrate.
The binding of the substrate to the enzyme causes changes in
the distribution of electrons in the chemical bonds of the substrate
and ultimately causes the reactions that lead to the formation
of products. The products are released from the enzyme surface
to regenerate the enzyme for another reaction cycle.
The active site has a unique geometric shape that is
complementary to the geometric shape of a substrate molecule,
similar to the fit of puzzle pieces. This means that enzymes
specifically react with only one or a very few similar compounds.
Lock and Key Theory:
The specific action of an enzyme with a single substrate can
be explained using a Lock and Key analogy first postulated
in 1894 by Emil Fischer. In this analogy, the lock is the enzyme
and the key is the substrate. Only the correctly sized key
(substrate) fits into the key hole (active site) of
the lock (enzyme).
Smaller keys, larger keys, or incorrectly positioned teeth
on keys (incorrectly shaped or sized substrate molecules) do
not fit into the lock (enzyme). Only the correctly shaped key
opens a particular lock. This is illustrated in graphic on the
QUES: Using a diagram and in your own words, describe the
various lock and key theory of enzyme action in relation to a
correct and incorrect substrate.