Millions of colors in the visible spectrum can be generated by mixing red, green and blue - the RGB color system. Is there a basic set of smells that, when mixed, can yield all, or nearly all detectable smells ?
There are about 100 (Purves, 2001) to 400 (Zozulya et al., 2001) functional olfactory receptors in man. While the total tally of olfactory receptor genes exceeds 1000, more than half of them are inactive pseudogenes. The combined activity of the expressed functional receptors accounts for the number of distinct odors that can be discriminated by the human olfactory system, which is estimated to be about 10,000 (Purves, 2001).
Different receptors are sensitive to subsets of chemicals that define a “tuning curve.” Depending on the particular olfactory receptor molecules they contain, some olfactory receptor neurons exhibit marked selectivity to particular chemical stimuli, whereas others are activated by a number of different odorant molecules. In addition, olfactory receptor neurons can exhibit different thresholds for a particular odorant. How these olfactory responses encode a specific odorant is a complex issue that is unlikely to be explained at the level of the primary neurons (Purves, 2001).
So in a way, the answer to your question is yes, as there are approximately 100 to 400 olfactory receptors. Just like the photoreceptors in the visual system, each sensory neuron in the olfactory epithelium in the nose expresses only a single receptor gene (Kimball). In the visual system for color vision there are just three (red, green and blue cones - RGB) types of sensory neurons, so it's a bit more complicated in olfaction.
- Kimball's Biology Pages
There are many, many more parameters than 200! As an example, look at the nomenclature system for olfactory receptors (ORnXm).
- "OR" is the root name (Olfactory Receptor superfamily)
- n = an integer representing a family (e.g., 1-56) whose members have greater than 40% sequence identity,
- X = a single letter (A, B, C, ...) denoting a subfamily (>60% sequence identity),
- m = an integer representing an individual family member (isoform)
Members belonging to the same subfamily of olfactory receptors (>60% sequence identity) are likely to recognize structurally similar odorant molecules.
So, if we have 56 families, and each family has 26 possible subfamilies that can each detect a specific range of molecules, then you have a 1456-characters "alphabet" to describe all possible smells. Now humans will have more or less of each type, some types will not be there but be present in dogs, etc... Now if you take any actual smell (complex molecules with multiple odorants), it will be represented by any number of specific receptors going on at the same time. So if we set a limit of 100 receptors activated simultaneously per whiff (imaginary, no idea what the real number is), there are 1456^100 possible combinations of receptor activations for any 100-odorants smell.
Glusman G, Bahar A, Sharon D, Pilpel Y, White J, Lancet D (November 2000). "The olfactory receptor gene superfamily: data mining, classification, and nomenclature". Mammalian Genome. 11 (11): 1016–23. doi:10.1007/s003350010196. PMID 11063259.
Malnic B, Godfrey PA, Buck LB (February 2004). "The human olfactory receptor gene family". Proceedings of the National Academy of Sciences of the United States of America. 101 (8): 2584–9. Bibcode:2004PNAS..101.2584M. doi:10.1073/pnas.0307882100. PMC 356993Freely accessible. PMID 14983052.
Glusman G, Yanai I, Rubin I, Lancet D (May 2001). "The complete human olfactory subgenome". Genome Research. 11 (5): 685–702. doi:10.1101/gr.171001. PMID 11337468.
Yes, it certainly is. But I cannot guarantee that all have been properly determined.
For that, we would have to find the basic unique values (like the Red, Green and Blue in the case of colors).
Currently, we have 10 unique human detectable smells: The wood-like smell, the floral/fragrant one, non-citrus, chemical, sharp(garlic-like), sweet, menthol, peanut-like, lemon and decay/dead-like (those are labeled by researchers as W1 to W10). A reference of the 10.
The your RGB-like-values for smell should be something like that.
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protected by AliceD♦ Jan 18 '17 at 9:07
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