Look at your hands. They’re basically reflections of each other, which is why they fit together when you clap. Pairs of shoes, gloves, and mittens all consist of reflections. You can tell a right shoe from its mate by looking at it. Scientists have discovered that molecules also come in "left-handed" and "right-handed" versions. And, as with shoes, whether a molecule is left or right changes how it fits into the big picture.
Small Changes Make Big Differences
Scientists say that a molecule is chiral if it exists in both left- and right-handed forms. Your body is very picky about which forms of molecules it will use to grow. Amino acids, the building blocks of proteins, must be left-handed for your body to use them. On the other hand, your body can only use right-handed sugars. Some food companies have used the chiral properties of molecules to make diet foods. Since your body can’t process left-handed sugars, manufacturers sometimes use them as artificial sweeteners. They have no calories because your body can’t digest them, but they still taste sweet.
Lemons and oranges both get their smell from the molecule limonene. However, since the handedness of the molecule is different in oranges and lemons, your nose perceives two different smells. Not all chiral molecules are safe. For instance, one form of the drug thalidomide prevents nausea, while the other causes severe birth defects; their confusion in the 1950s and 1960s caused thousands of babies to be born with deformities to mothers who had taken thalidomide to alleviate their morning sickness during pregnancy. In order to make safe medications, scientists must be able to sort the left-handed molecules from the right-handed ones.
See for yourself: http://www.youtube.com/watch?v=71GjsRnsoL8
Visit the links below to learn more about molecular chirality and its real-life effects and applications.