Final answer:
There are five primary taste sensations: sweet, sour, bitter, salty, and umami. Each is received by a specific receptor that is tuned to its particular molecular structure, and recent studies suggest the potential existence of a sixth taste for fats or lipids.
Step-by-step explanation:
The five basic taste sensations are characterized as a type of gustatory sensation. Taste, or gustation, in humans is broken down into five primary categories: sweet, sour, bitter, salty, and umami.
Each of these tastes corresponds to specific receptors on the tongue that detect different types of tastants. For example, salty tastants, containing NaCl, provide sodium ions that directly excite taste neurons.
Sour tastants, which are acids, belong to the thermoreceptor protein family and increase the hydrogen ion concentrations in taste neurons, depolarizing them. Sweet, bitter, and umami tastants bind to their G-protein coupled receptors, which excite specialized neurons associated with these tastes.
Umami, a term that translates to 'yummy' or 'savory,' is associated with the taste of monosodium glutamate and high-protein foods. Additionally, recent research suggests that there may be a sixth taste for fats or lipids, although this is not yet widely recognized.