Re: how is chemistry related to pharmocology?

One caveat first.  I assume you really mean pharmacology, not pharmacy.  
They are quite different things.  Pharmacy is (usually) simply dispensing 
medicines, you local pharmacist at the drug store.  Pharmacology is the 
study of how drugs and hormones and other things work, how do they 
influence cellular or tissue or organismal function.  If you mean 
pharmacy, you need a little chemistry to understand what it is you'll 
dispense, what's incompatible or not.  But if you're a pharmacologist, you 
need to know a lot of chemistry (see below).  Now before all the 
pharmacists come after me, I should say that there is a professional 
degree known as a "Doctorate in Pharmacology" or Pharm.D. (just like M.D. 
means medical doctor).  These folks know a lot more pharmacology that 
doctors or pretty much anyone else.  If you're a physician, get to know 
your local Pharm.D. at the hospital (and hopefully your hospital will have 
one).  A Pharm.D.'s advice is invaluable in preventing drug interactions, 
adverse effects, determining the proper dosage, considering alternative 
drugs fo the same disease, etc. About 100,000 people die each year from 
adverse drug reactions in hospitals.  If you're a physician, get to know 
your Pharm.D.  You'll greatly reduce the chances that you will add to that 
statistic.

Chemistry is the heart of pharmacology.  Pharmacology is the study of 
how "drugs" (which can be darn near anything) interact with various 
hormone receptors or other pathways in an organism.  The "drugs" are 
almost always small molecules, that is, they are "chemicals".  The trick 
in developing and using drugs is to get "selective" drugs, drugs that 
interact with one or only a few if the receptors/pathways in the body.  
Virtually all drugs are "dirty", they interact in multiple places and 
cause different effects, some of which you'll want (therapeutic effects) 
and some not (toxic or adverse effects).  Where chemistry comes in is at 
all levels.  If you're a chemist or biologist in a drug company, you need 
to know the chemical structure of your potential drug.  That way, you can 
make lots of minor changes in that chemical to see if you can make it more 
selective.  A physician doesn't do that, but a physician needs to know 
enough chemistry to understand the biology.  Chemistry underlies biology 
in the sense that it is individual chemicals (some of them small like most 
hormones, amino acids, sugars, etc. and some of them large (proteins, DNA, 
etc.) that interact to keep a cell alive, give it structure, produce 
energy, generate movement, even eventually generate thought.  If I am 
doing basic research in some aspect of biology/pharmacology, I really need 
to know the chemicals I am dealing with, for major and minor reasons.  For 
example, I need to understand pH and acids and bases to understand why pH 
is important for protein stability and for metabolism, why alterations in 
blood or tissue or cellular pH are not exactly good for you.  I need to 
understand acid-base chemistry to understand that the kidney will 
eliminate some drugs very well and not others because of their acid-base 
characteristics and further that I can help the kidney eliminate some 
drugs by giving another drug that changes the pH of the urine.  I need to 
understand at least some small amount of chemistry to understand why and 
to predict that if I give my child "Ventolin" for lung congestion or croup 
that it will help them breath.  It will also make their heart rate and 
blood pressure go up.  It works in the heart by a different pathway than 
in the lungs.  If you know a bit of chemistry, that will make sense to 
you.  If you don't, it's just memorization with no real understanding.  If 
you don't understand the basics as a physician, you'll make mistakes.

From another perspective, I've hired many postdocs and technicians and had 
many graduate students in my laboratory over the last 25 years.  I've 
discovered that they can readily learn biology even if they haven't had 
much before IF they've had chemistry.  But if all they've ever taken is 
biology and they never took or blew off their chemistry, it's too late.  
I've never been able to teach them the necessary chemistry for their 
work.  It's not that I do "chemistry" in my lab, but they make much poorer 
techs or students if they cannot use at least a little bit of chemistry.