T.A. Mona L
March 22, 2011
In the living organisms, reactions occur every second. Two prime examples of
these reactions are dehydration and hydrolysis. Dehydration is a process where complex
molecules are synthesized from smaller molecules by the removal of water. Hydrolysis is
the opposite process in which complex molecules are broken into simpler molecules by
the addition of water. Both processes occur naturally in organisms, but happen at
extremely slow rates.
Organic catalysis also known as enzymes, are normally proteins, however there
have been many enzymes made up of RNA nucleic acid. Enzymes are catalytic proteins,
meaning they speed up chemical reactions without being used up or altered permanently
in the process. Although various enzymes use different methods, all accomplish catalysis
by lowering the activation energy for the reaction, thus allowing it to occur more easily.
Enzymes have very specific shapes (conformations). Part of the conformation is the
active site of the enzyme, where the actual catalysis occurs. The specific molecule or
closely related molecules on which an enzyme functions is known as its substrate. Shape
plays such an important role in enzymatic catalysis that often even isomers of a substrate
will be rejected. Once the substrate enters the active site, it may begin a process known as
induced fit in which the enzyme perfectly conforms to the molecule to allow for more
efficient catalysis. Changes in environment can severely impact enzyme catalysis in both
negative and positive ways. Each enzyme has specific ranges at which it optimally
functions; in general, increasing the temperature will help the reaction along, until the
point at which the protein degrades and denatures. Denatured proteins will often return to
their original state, after the removal of the denaturing agent, except when they are
degraded multiple levels. Without altering the physical integrity of the cell, enzymes can
change the rate of a cell’s chemical reaction. Enzymes are never used nor changed in the
reaction. Therefore, they can be recycled to break down additional substrate molecules.
Being proteins, enzymes have a highly organized structure which dictates its specificity
for substrates. The primary structure of an enzyme includes its amino acid arrangement.
This arrangement then controls the secondary and tertiary structures, which are
intermolecular bonds forming between amino acids and their side chains, creating a
three-dimensional conformation. If the shape of the enzyme is denatured or interrupted,
then the enzyme will not function properly. Each active site has its own unique enzyme.
There is a specific substrate that fits the active site of certain enzymes. Variations in
temperature, salt, ion concentration and hydrogen ion concentration may change the
active site as well as, the enzyme. Any of these factors could denature the enzyme by the
denaturing the protein structure.