Question

How does the effectiveness of one enantiomer and not the other illustrate the theme of structure and function?

Answer 1

Can you put your left shoe onto your right hoof?

Explanation:

And your right shoe onto your left hoof? Perhaps you can, but I doubt that you will be able to walk comfortably. I don't think there is much else that I can say with regard to handedness and structure. As to how to separate enantiomers, see this site.