Why must odor molecules dissolve in nasal mucus before they can be detected?

Odor molecules must dissolve in the nasal mucus to be detected because the olfactory receptor cells, which are located within the olfactory epithelium, require chemicals to be in a dissolved state to stimulate them chemically.1

Many volatile compounds that reach the nose are not naturally water-soluble. The mucus serves as a medium that facilitates the interaction between these odorants and the sensory nerve endings. For compounds that are not easily soluble, the body utilizes soluble proteins present in the mucus to bind with the molecules, allowing them to move freely through the fluid and reach the receptors. Once these particles are dissolved or transported to the receptor membrane, they trigger the chemical stimulation necessary for the sense of smell. Additionally, the mucus environment helps maintain the sensitivity of the system by using odorant-degrading enzymes to remove molecules once they have been detected, ensuring the system remains responsive to new stimuli.231