A level biology helpWatch this thread
Enzyme inhibitors basically prevent a substrate from being catalysed by an enzyme so it's reaction can't be completed.
There are 2 kind of inhibitors, competitive and noncompetitive. Competitive inhibitors block the enzyme's active site, so the natural substrate can't enter the active site of the enzyme, and therefore can't be catalysed by it. Noncompetitive inhibitors bind to the enzyme but not the active site; an allosteric site, this changes the shape of the active site so the substrate can't be catalysed.
Some examples include cyanide, which irreversibly inhibits a respiratory enzyme, preventing ATP production. Obviously if no ATP can be produced the body is in a bit of trouble, hence why it's a poison. Statins are reversible competitive inhibitors that inhibit a cholesterol producing enzyme. Why is it important that they're reversible?
Some other examples you might be interested in (though probably won't have to memorise all the detail of) include organophosphates and aspirin (aspirin can get complicated, just an outline will do.)