SaltinessSaltiness is a taste produced best by the presence of cations (such as Na+, K+ or Li+) and is directly detected by cation influx into glial like cells via leak channels causing depolarisation of the cell.Other monovalent cations, e.g., ammonium, NH+4, and divalent cations of the alkali earth metal group of the periodic table, e.g., calcium, Ca2+, ions, in general, elicit a bitter rather than a salty taste even though they, too, can pass directly through ion channels in the tongue. SournessSourness is acidity, and, like salt, it is a taste sensed using ion channels. Undissociated acid diffuses across the plasma membrane of a presynaptic cell, where it dissociates in accordance with Le Chateliers principle. The protons that are released then block potassium channels, which depolarise the cell and cause calcium influx. In addition, the taste receptor PKD2L1 has been found to be involved in tasting sour. BitternessResearch has shown that TAS2Rs (taste receptors, type 2, also known as T2Rs) such as TAS2R38 are responsible for the ability to taste bitter substances in vertebrates. They are identified not only by their ability to taste certain bitter ligands, but also by the morphology of the receptor itself (surface bound, monomeric). SavorinessThe amino acid glutamic acid is responsible for savoriness, but some nucleotides (inosinic acid and guanylic acid) can act as complements, enhancing the taste.Glutamic acid binds to a variant of the G protein-coupled receptor, producing a savory taste. Further sensations and transmission
The tongue can also feel other sensations not generally included in the basic tastes.
Other concepts
Supertasters
A supertaster is a person whose sense of taste is significantly more sensitive than most. The cause of this heightened response is likely, at least in part, due to an increased number of fungiform papillae. Studies have shown that supertasters require less fat and sugar in their food to get the same satisfying effects. However, contrary to what one might think, these people actually tend to consume more salt than most  people. This is due to their heightened sense of the taste of bitterness, and the presence of salt drowns out the taste of bitterness. (This also explains why supertasters prefer salted cheddar cheese over non-salted.) Aftertaste
Aftertastes arise after food has been swallowed. An aftertaste can differ from the food it follows. Medicines and tablets may also have a lingering aftertaste, as they can contain certain artificial flavor compounds, such as aspartame (artificial sweetener). Acquired taste
An acquired taste often refers to an appreciation for a food or beverage that is unlikely to be enjoyed by a person who has not had substantial exposure to it, usually because of some unfamiliar aspect of the food or beverage, including bitterness, a strong or strange odor, taste, or appearance. Clinical significance
Patients with Addisons disease, pituitary insufficiency, or cystic fibrosis sometimes have a hyper-sensitivity to the five primary tastes. Disorders of taste
ageusia (complete loss of taste)
hypogeusia (reduced sense of taste)
dysgeusia (distortion in sense of taste)
hypergeusia (abnormally heightened sense of taste)Viruses can also cause loss of taste.