# what is the difference between how taste and smell are detected?

Taste and smell are both chemical processes

... parts of the food dissolved in saliva come into contact with the taste receptors.[1] These are located on top of the taste receptor cells that constitute the taste buds. The taste receptor cells send information detected by clusters of various receptors and ion channels to the gustatory areas of the brain via the seventh, ninth and tenth cranial nerves. (https://en.wikipedia.org/wiki/Taste_bud)

, is there any difference in the way taste and smell receptors work?

• Seeing, hearing, touching and thinking are chemical processes as well. Should then throw biology sciences out ? – Poutnik Jun 12 '19 at 7:55
• @Poutnik, en.wikipedia.org/wiki/Flavor, says there are only three chemical senses – user157860 Jun 12 '19 at 8:32
• You wrote processes, not senses. Still, you should ask neurologists, not chemists. – Poutnik Jun 12 '19 at 8:39
• Beside biology, neurology and psychology aspect are often neglected when we deal with human as detectors. This is another example along with many about optical phenomena. Ask in Biology SE. – Alchimista Jun 12 '19 at 10:57
• I have not said there are 3 chemical senses. – Poutnik Jun 12 '19 at 13:18

Proteins are almost certainly the 'detectors' for both smell and taste, so chemistry is at the heart of the process. For airborne chemicals these will have to diffuse through some form of 'mucus' before reaching the cells in your nose on the surface of which are the receptor proteins. Typically these would span the cell membrane. Interaction of the smell/taste molecule with the protein (in an active site usually inside the protein) may cause some ions to be transported though the protein and so into, or out of the cell, and which eventually gives us the sensation. Clearly the whole process is very complex to say the least. Bacteriorhodopsin works in this way (although process is initiated by light) and this process has been called isomerisation-switch-transfer (see Oesterhelt Biochem. 1977,36,p2) but the idea is generic.

The trigger would be your smell or taste molecule that causes a conformational change in the protein, the proton gradient produced is then used to drive other chemistry that results after many steps, in a sensation. The very crude figure below gives the essence of the detection idea.

Taste receptors work with water (or saliva, or whatever other liquid that happens to occur in your mouth) and the things dissolved therein.

Smell receptors work with air and airborne chemicals.

Short of that, they are similar in that both are wide-range chemical sensors, and different in that they send different signals to our brain.

• Thanks, what is the difference in the signals they send? are signal electrical , chemical or what? – user157860 Jun 12 '19 at 8:26
• @user157860 Ask rather neurology resources. – Poutnik Jun 12 '19 at 8:38
• Not to answer: not necessarily different by their nature, but by their meaning – Poutnik Jun 12 '19 at 8:52
• That's right: both are nerve signals (which are both electrical and chemical in nature), but they convey different information to our brain. – Ivan Neretin Jun 12 '19 at 8:54

Both taste and smell are not that well understood yet. Here is a summary of some of the chemistry and physiology.

Types of substances detected

The sense of smell detects volatile substances. As stated in porphyrin's answer, scent molecules dissolve in aqueous solution and then reach the transmembrane receptors. The sense of taste detects substances dissolved in saliva, typically after they are ingested. That way, non-volatiles like sodium chloride or sucrose can also reach the taste buds.

Channels and receptors

Substances are detected by transmembrane proteins that either act as channel or receptor. Channels selectively take up e.g. $$\ce{H+}$$ or ions, triggering a downstream response in the cell. Receptors bind to a ligand and change conformation, triggering a downstream response in the cell (e.g. G-protein coupled receptors). There is a hypothesis that the taste of "sour" and the taste of "salty" might involve selective ion channels.

What triggers a given taste or smell?

Tasting is a combination of what taste receptors detect with other information (notably from smell of volatiles traveling from the back of the mouth into the nose). There are only a handful of tastes. Each receptor seems to be linked to only one of them. For smell (olefaction), one substance will trigger multiple types of receptors, and one receptor will be triggered by multiple substances. The combination of receptor types firing gives rise to the perception of a certain smell. This (along with the higher number of different receptors compared to the taste buds) explains why we can distinguish more smells than tastes.