3.   The mechanism of enzyme action is well illustrated by the ‘‘lock and key” analogy.
      The ‘‘lock” represents the substrate and the ‘‘key” represents the enzyme.
      Just as a key is specific for a certain lock, an enzyme is specific for a certain
      substrate. Also, just as the enzyme has an ‘‘active site” where the chemistry
      occurs when it combines with a substrate, the key has grooves and notches
      that must match those in the lock mechanism. After the key ‘‘opens” the lock
      remains intact, just as the enzyme reappears intact after acting on a substrate.

 

4.   A new theory of enzyme activity is the “induced fit” model, where the enzyme
      conformation changes to accommodate the substrate. This is somewhat like
      a glove changing to fit the hand inserted into it.
 

Pictures in the Mind                             

1.   Draw a picture of an
      enzyme molecule. Each
      circle represents an
      amino acid. Typical
      amino acids are shown
      here.
 
 

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