Shape theory of olfaction

From Wikipedia, the free encyclopedia

The Shape theory of smell states that the sensation of smell is due to a 'lock and key' mechanism by which a scent molecule fits into olfactory receptors in the nasal lamina of the nose. This theory is currently the most widely accepted explanation for animal olfaction in fields such as neural anatomy, biochemistry and biology, which conducts research in the sensory sciences.

[edit] Support

Dr. John E. Amoore came up with the shape theory in 1952 at Oxford University. Dr. Amoore postulated that seven primary odors combine in various ways to form all odors. The seven primary odors include sweaty, spermous, fishy, malty, urinous and musky. It is well proven that the olfactory receptors in all higher animals are special types of G-protein-coupled receptors. Since all types of G-protein receptors known to modern science are activated through binding of molecules with highly specific conformations, or shape, it is assumed that olfactory receptors operate in a similar fashion.

Since only 347 olfactory receptors have been discovered in the human nose, it is assumed that humans distinguish between a multitude of experienced smells through a complex relationship between the receptors and the odorous molecules. This includes:

Specific binding of certain molecular functional groups by one or many receptors
Loose binding of molecular structures and functional groups with similar shapes by one or many receptors
Specific binding of molecular elements in certain spacial conformations

It is generally believed that signals from different olfactory bulb neurons are combined and processed by the brain, which results in the perception of different scents.

Numerous studies have been conducted such as to elucidate the complex relationship between the shape of an odorous molecule and its perceived smell character.