What makes enantiomers so special?
Enantiomers have different physical arrangement of atoms. This difference plays a crucial role in biology.


  But, why do enantiomers have different biological activities?
  
  Recognition of chiral drugs by specific drug receptors is explained by
  a three-point interaction of the drug with the receptor site, as
  proposed by Easson and Stedman. The difference between the interaction
  of the two enantiomers of a chiral drug with its receptor is
  illustrated below.
  
  
  
  Source: https://www.khanacademy.org/test-prep/mcat/chemical-processes/stereochemistry/a/chiral-drugs