Amino acids are an example of how important enantiomers are, there are both R and S (or D and L since it's a biochemical compound) amino acids. Our body uses ONLY the L-amino acids, which is pretty neat.
As for conformers or structural isomers, I'd do some googling as I can't think off the top of my head of an example. I know I have heard of a drug that with a hydrogen at one position, it's a helpful drug, but if the hydrogen is switched to another position, it becomes a deadly neurotoxin.