Our Sense of Smell
1 Our Sense of Smell
- Facts about smell
- Mechanism
- Genetic implications
- Structure and odor
2 Our Nose
3 Detecting Odors
4 The Olfactory Bulb
5 Sensitivity
Odor threshold: Lowest concentration of an odor our noses can detect. Can be less than one part per trillion in air. Much more sensitive than most analytical instrumentation.
Examples:
| Molecule | Min. mass | # of molecules |
| ethyl mercaptan | 10 -13 g | 10 9 molecules |
| vanillin | 5 x 10 -12 g | 2 x 10 10 molecules |
| naphthalene | 4 x 10 -12 g | 2 x 10 10 molecules |
6 Volume Air
We breathe ~ 12,000 times/day
Volume of air moved:
- 12 meters 3 @ 3000 gallons
Approximately the volume of air in a single room
7 Genetic Importance
Human genome contains ~ 30,000 genes
Thus, ~ 3% of DNA genes code for scent
This is the largest group of related genes discovered to date.
8 Structure/Function
No simple relationships known.
- Some sets of very dissimilar molecules have similar odors.
- Some very similar molecules have different odors.
Examples: (see also Leffingwell site)
- carvone: smells like spearmint [R-(-)] or caraway [S-(+)]
- limonene: smells like orange [R-(+)] or turpentine [S-(-)]
9 Vanillin, Cloves, and Spice
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10 Esters
|
| Odor | R 1 | R 2 |
| rum | H | CH 2 CH 3 |
| pear | CH 3 | CH 3 CH 2 CH 2 CH 2 |
| pineapple | CH 3 CH 2 CH 2 | CH 3 CH 2 CH 2 |
| strawberry | CH 3 CH 2 CH(CH 3 ) | C 10 H 21 |
| apple | CH 3 CH 2 CH 2 CH 2 CH 2 | CH 2 CH 3 |
| grape | C 9 H 19 | CH 2 CH 3 |
File translated from TEX by TTH, version 3.02.
On 19 Nov 2001, 16:41.