All of the functional groups of a drug are important because

1. they catalyze biochemical reactions.

2. they interact with specific receptor sites
using molecular recognition.

3. signaling pathways depend upon pH
which, in turn, depends upon the number
and kinds of organic acid and base functional
groups.

4. solubility of drugs in cell membranes
depends upon hydrophobic interactions.

5. they form covalent bonds with amino acids
residues of proteins.

Any help?

all of the groups interact with the receptor sites, for good things and bad things (unwanted side effects)