UNRAVELING THE SENSE OF SMELL

The Nobel Lecture, December 8, 2004
by
Linda B. Buck
Howard Hughes Medical Institute, Fred Hutchinson Cancer Research
Center, 1100 Fairview Avenue North, Seattle, WA 98109–1024, USA.

INTRODUCTION
The subject of my lecture is the sense of smell, one of the five senses through
which we perceive the world. Through the sense of smell, humans and other
mammals can perceive a vast number and variety of chemicals in the external
world. It is estimated that humans can sense as many as 10,000 to 100,000
chemicals as having a distinct odor. All of these “odorants” are small, volatile
molecules. However, they have diverse structures and somehow those different
structures are perceived as having different odors (Figure 1).
The sense of smell is mediated by the olfactory system, a system that is characterized
by exquisite sensitivity and discriminatory power. Even a slight
change in the structure of an odorant can change its perceived odor. For
example, the close relative of a chemical that is perceived as pear can have
the scent of an apple. In addition to odorants, the olfactory system detects
pheromones, chemicals that are released from animals and act on members
of the same species, stimulating hormonal changes or instinctive behaviors,
such as mating or aggression. The olfactory system also detects predator
odors, which can elicit innate fear responses.