taste (sense)

Sense that detects some of the chemical constituents of food. The human tongue can distinguish five basic tastes: sweet, sour, bitter, salty, and ‘umami’ (a taste sensation triggered by the amino acid glutamate). However, what we refer to as taste is really a composite sense made up of both taste and smell.

Umami is now called L-glutamate and a specific molecule receptor for it has been identified in taste buds.

In terms of evolution, the receptors for the five basic tastes can each be associated with a specific survival function. Sweet, salty, and ‘umami’ serve the recognition of food rich in carbohydrates, minerals, and protein. Sour and bitter tastes presumably evolved as warning signs against acids and natural poisons.

Receptor molecules for taste sensation remained elusive until 2000, when systematic search of the human genome enabled researchers to identify the genes and then investigate the proteins in detail. Like many other signalling events, taste sensation was found to involve a specific G protein (called gustducin), thus taste receptors belong to the large family of G-protein coupled receptors.