Taste

Biology: Cambridge International A Level, topic 15.1.3

Taste (gustation) is called a chemical sense because it requires sensory receptors that respond to molecules in the food we eat.

You have learned since primary school that there are four basic groupings of taste: sweet, salty, sour, and bitter.
Research demonstrates, however, that we have at least six taste groupings.
Umami is our fifth taste.
Umami is actually a Japanese word that roughly translates to yummy, and it is associated with a taste for monosodium glutamate.
There is also a growing body of experimental evidence suggesting that we possess a taste for the fatty content of a given food.

Molecules from the food and beverages we consume dissolve in our saliva and interact with taste receptors on our tongue and in our mouth and throat.
Taste buds are formed by groupings of taste receptor cells with hair-like extensions that protrude into the central pore of the taste bud.
Taste buds have a life cycle of ten days to two weeks, so even destroying some by burning your tongue won’t have any long-term effect; they just grow right back.

Taste molecules bind to receptors on this extension and cause chemical changes within the sensory cell.
These changes include the opening of ion channels and the depolarisation of receptors.
For example, Na⁺ ions can flow through ion channels in certain taste buds, leading to the detection of a "salty" taste.
The opening of ion channels depolarises the receptor. This creates an action potential in a sensory neuron.
Taste information is transmitted via the sensory neuron to the gustatory cortex in the brain.

Test yourself on Taste