Explain the receptor site theory and how it applies to smell detection

Receptor Site Theory is a widely accepted theory of how the interior of the nose detects different smells. The receptor site theory uses the 'lock and key' model. In this model, molecules are like 'keys' that fit into only certain 'locks.' In other words, molecules have specific shapes that will fit only certain receptor sites, and the lining of the nose is covered with receptor sites.