Final answer:
Olfactory receptor proteins located on the membrane of nonmotile cilia are coupled to G-proteins, which help in the detection and signalling of odor molecules leading to the perception of smell.
Step-by-step explanation:
Olfactory receptor proteins are especially located on the membrane of nonmotile cilia of olfactory neurons and are coupled to G-proteins. These receptors are responsible for the detection of odorant molecules that are inhaled into the nasal cavity and dissolve in the mucus. The odorant-protein complex binds to the G protein-coupled receptor within the cell membrane of an olfactory dendrite, which then produces a graded membrane potential in the olfactory neurons, leading to the perception of smell.