Question

Why does nature use only one ‘handedness’ for organic molecules but both ‘hands’ for inorganic ones?

The origin of homochirality in living organisms on Earth has puzzled scientists for as long as stereochemistry has been observable. In fact, this problem is one of the objectives of astrobiology research: http://astrobiology.arc.nasa.gov/roadmap/goals/g2_organiz_matter.html.. No universally accepted answer exists; however, there are at least two main theories in contention. The more generally accepted idea is that there was a chance proliferation and eventual dominance of one type of "handedness" through an ancient protein polymer acting as a template for selection. The second theory holds that transfer RNA may have originally selected specific enantiomers during messenger RNA decoding, driven by the small effects of the earth's magnetic field. Therefore, planetary magnetic fields, though generally regarded as too weak to generate enantioselective molecules, are still a possibility. You may want to check out this reference on the influence of magnetic fields on enantioselection: Rikken, G.L.J.A. and Raupach, E., "Enantioselective magnetochiral photochemistry." Nature 405(6789):932-5, 22 June 2000.
May 1, 2002