There is no chance about it...

Molecules interact with eachother because of their electronegative/electropositive qualities. Just think of a magnet...only think of all different kinds of magents that you can assemble together to make even more specific magnets that only bind to certain magnets...

Now take that idea, and multiply it by 1,000,000... and you now have modern biochemistry.

Yea, that shit definately happened by chance.