Search Results - Hypothetical types of biochemistry

Perhaps the least unusual alternative biochemistry would be one with differing chirality of its biomolecules. In known Earth-based life, amino acids are almost universally of the L form and sugars are of the D form. Molecules of opposite chirality have identical chemical properties to their mirrored forms, so life that used D amino acids and/or L sugars may be possible; molecules of such a chirality, however, would be incompatible with organisms using the opposing chirality molecules. It is questionable, however, whether such a biochemistry would be truly alien; while it is certainly an alternative stereochemistry, molecules that are overwhelmingly found in one enantiomer throughout the vast majority of organisms, can nonetheless often be found in another enantiomer in different (often basal) organisms, such as in comparisons between members of Archea and other domains, making it an open topic whether an alternative stereochemistry is truly novel.

Scientists have speculated about the pros and cons of using atoms other than carbon to form the molecular structures necessary for life, but no one has proposed a theory employing such atoms to form all the molecular machinery necessary for life. Since humans are carbon-based beings and have never encountered any life that exists outside the earth’s environment, excluding the possibility of all other elements may be considered carbon chauvinism.

The most commonly proposed basis for an alternative biochemical system is the silicon atom, since silicon has many chemical properties similar to carbon and is in the same periodic table group, the carbon group.