ABSTRACT
The task of a chemical sense organ is to detect and recognize specific molecules. However, the number of organic compounds which may function as odorants is virtually endless, and natural flavors may consist of hundreds of different substances. Olfactory receptors, on the other hand, show a puzzling variety of individual specificities. Odor qualities cannot be arranged along a linear scale like colors are according to wavelength. Multiple independent variations in the structure of a molecule result in a multidimensional “space” of odor qualities. Therefore, it is often difficult for an investigator to find the adequate natural stimulus for a chemoreceptor, or even to search for it systematically without knowing the biological context.
