Sweet, bitter, and umami tastes, however, are detected by way of G protein-coupled taste receptors. Salty and sour taste sensations are both detected through ion channels. Five basic tastes are recognized today: salty, sweet, bitter, sour, and umami.

Taste helps to identify toxins, maintain nutrition, and regulate appetite, immune responses, and gastrointestinal motility. This receptor is also found in the bladder, suggesting that consumption of artificial sweeteners which activates this receptor might cause excessive bladder contraction. The sweet taste receptor found in the gut and in the pancreas was found to play an important role in the metabolic regulation of the gut carbohydrate-sensing process and in insulin secretion. In most of the organs, the receptor function is unclear. The sweet taste receptor (T1R2/T1R3) can be found in various extra-oral organs throughout the human body such as the brain, heart, kidney, bladder, nasal respiratory epithelium and more. They believe this mechanism is evolutionarily adaptive because it helps clear lung infections, but could also be exploited to treat asthma and chronic obstructive pulmonary disease. In 2010, researchers found bitter receptors in lung tissue, which cause airways to relax when a bitter substance is encountered. Next to the taste receptors in on the tongue, the gut epithelium is also equipped with a subtle chemosensory system that communicates the sensory information to several effector systems involved in the regulation of appetite, immune responses, and gastrointestinal motility The glossopharyngeal nerve and the chorda tympani branch of the facial nerve innervate the TAS1R and TAS2R taste receptors. There are three cranial nerves that innervate the tongue the vagus nerve, glossopharyngeal nerve, and the facial nerve. Beyond the papillae, taste receptors are also in the palate and early parts of the digestive system like the larynx and upper esophagus. (The fourth type - filiform papillae do not contain taste buds). There are three types of papillae involved in taste: fungiform papillae, foliate papillae, and circumvallate papillae. Taste buds, in turn, are contained in structures called papillae. The gustatory system consists of taste receptor cells in taste buds. Of these, transient receptor potential cation channel subfamily V member 1 ( TRPV1) vanilloid receptors are responsible for the perception of heat from some molecules such as capsaicin, and a CMR1 receptor is responsible for the perception of cold from molecules such as menthol, eucalyptol, and icilin. Visual, olfactive, 'sapictive' (the perception of tastes), trigeminal (hot, cool), mechanical, all contribute to the perception of taste.

Type 2, bitter, first characterized in 2000: In humans there are 25 known different bitter receptors, in cats there are 12, in chickens there are three, and in mice there are 35 known different bitter receptors.Type 1, sweet, first characterized in 2001: TAS1R2 вЂ“ TAS1R3.Vertebrate taste receptors are divided into two families: Molecules which give a sensation of taste are considered 'sapid'. When food or other substances enter the mouth, molecules interact with saliva and are bound to taste receptors in the oral cavity and other locations. A taste receptor is a type of cellular receptor which facilitates the sensation of taste.

How many taste buds do humans have