Chemoreception is a sensory system used by organisms to detect chemicals in the environment. There are two primary forms of chemoreceptors: gustatory and olfactory, which are responsible for the senses of taste and smell. In this process, molecules interact directly with receptor sites to initiate reactions which the brain interprets as sensory data.

For example, olfactory receptor cells in vertebrates and marine invertebrates are arranged in various places where they are in contact with air or water which carries the molecules to be detected. These receptors are embedded in a layer of supporting cells below the surface. One end of the receptor cell extends to the epithelium where it forms a knob-like projection with cilia protruding from it; the other end of the receptor cell connects to a neuron. The supporting cells secrete a layer of mucous that covers the cilia of the receptor cell. The molecules being...