Optical isomeres and amino acids

In terms of chemistry isomers are compounds that have an identical molecular formula but a different structural formula, which means that its atoms are differently geometrically arranged. There are several forms of isomers and one that will be looked more closely into is stereoisomerism.

If you look at your nose in the mirror, the reflection will be identical to your real nose. If you instead would look at you palm in the mirror it would look exactly as your left hand. The reflection is not superposed, which is the reason you cannot fit you left hand into your right glove. An optical isomer (stereo isomer) is a mirror reflection of a compound. All compounds are not able to form optical isomers as the mirror image will be identical to the original object. This is just like the example with the nose, achiral objects. For stereoisomerism to occur, the compound needs to bee chiral. This happens when there is a fixed center with three different groups; atoms or molecules boned to it. These kinds of isomers have identical chemical properties and perform identical chemical reactions. They can only be distinguished in the direction they bend light. 

In biological terms optical isomers can have significantly different behaviors. There was an incident in the late 1950s with a drug called Thalidomide and was used by pregnant women against morning sickness. It resulted in children being born with various deformations which were caused by the optical isomer from of the compound. These are the devastating effects stereoisomerism can have.

All life is based on amino acids, more precise on the optical isomer L-amino acids. Amino acids are chiral which means that there are optical isomers; L-amino acids and D-amino acids. If a pathogen was artificially created that was based on the D-amino acid, all organism on earth would not be able to defend themselves against this microorganism. White blood cells of animals would have no effect against them as they were designed to fight pathogens of the same amino acid build up. If someone would create an organism like this, they would have the power to destroy all life on earth.