What are enzymes?

[Robert Zellmer]

In lecture I discussed enzymes.  These are catalysts in biological systems.
The book discusses active sites, the location of the enzyme where the
reaction takes place.  That's the site at which the substrate (reactant)
binds to the enzyme.  It can do so in different ways, the simplest picture
of which is called the lock-and-key model.  The active site requires a
molecule with the correct shape and arrangement of atoms in order for
the molecule to fit in the active site, like a key in a lock. Sometimes
different molecules within a class can fit into the same site because the
structure that interacts with the active site is the same, even though the
rest of the molecule is slightly different.  That's like the enzyme that
catalyzes methanol (CH3OH), ethanol (CH3CH2OH) and isopropyl
alcohol (CH3-CH(OH)-CH3, the OH is on the middle carbon).  They're
not that much different in size and have the -OH functional group.

As I stated, in methanol poisoning, the methanol is converted to
formaldehyde and then formic acid, not good for your organs.  It takes
much less of this to kill you than ethanol.  Even if you do survive it can
cause lasting damage to your organs, especially your eye site. Either
one can act as an inhibitor, or competitor, for the other.  When you
overdose on methanol one method to overcome this is essentially "flood"
your blood with ethanol.  There will be so much more ethanol than
methanol the ethanol molecules can occupy most of the active sites so
the methanol can't and the methanol eventually gets flushed out of your
system.

Enzymes are discussed on pages 603-606 of the 14th edition.

Dr. Zellmer