Tongue chemical receptors {taste receptor} are for sweet, sour, salty, bitter, and L-glutamate. Receptor cells have 50 chemoreceptors, all of the same receptor type, which detect positive ions or polarity.
Tongue chemoreceptors detect L-glutamate and other amino acids. Some receptors {glutamate receptor} {umami receptor} are metabotropic receptors similar to brain glutamate receptors and underlie savory taste (Kikunae Ikeda) [1908]. People with glutamate receptors can detect monosodium glutamate. Other receptors {amino-acid receptor} are altered sweet receptors that bind amino acids. Glutamate and amino-acid receptors couple to G-proteins, which have unknown second messengers.
Tongue chemoreceptors {salt receptor} detect positively charged salt ions, including sodium and potassium ions. Sodium-chloride sodium ions make pure salt taste. Potassium-chloride potassium ions make salt and bitter taste. Positive ions enter ion channels and directly cause depolarization.
Newborns do not taste salt, but babies soon can taste it, and they like it. Perhaps, salt receptors evolved because animals need sodium and need associated chloride.
Glasorisic acid increases sodium-ion retention.
Tongue chemoreceptors {sour receptor} detect acids. Acid hydrogen ions enter ion channels, block potassium channels, or bind to and open other positive-ion channels. Newborns can taste sour. Children like sour taste. Perhaps, sour receptors evolved to detect food or dangerous acidic conditions.
Tongue chemoreceptors {sweet receptor} detect non-ionic organic compounds, mostly sugars. Sweet-receptors couple to G-proteins, and second messengers close potassium channels. Newborns can taste sweet and like it. Perhaps, sweet receptors evolved to detect sugar nutrients.
Asclepiad, similar to milkweed, inhibits tasting sweet. African miraculous berry makes everything taste sweet. Artificial sweeteners mimic sugar molecules.
Proteins {T1R proteins} can make cell-membrane taste chemoreceptors. Sweet receptor has one T1R2 and one T1R3 protein. Umami savory receptor has one T1R1 and one T1R3 protein. Bitter receptor has 25 possible proteins.
Thirty different chemoreceptors {bitter receptor} detect non-ionic organic compounds, such as alkaloids, including quinine and unripe-potato alkaloid {solanine}. Bitter receptors couple to G-proteins. Second messengers release calcium ions from endoplasmic reticulum. All bitter-receptor types synapse on same taste-neuron type, so people cannot discriminate among bitters. Babies can taste bitter and dislike it. Perhaps, bitter receptors evolved to detect poisons.
6-n-propylthiouracil (PROP) tastes bitter. Supertasters have its chemoreceptors {6-n-propylthiouracil taste receptor}, have many fungiform papillae, and have high-intensity tastes. One-third of people cannot taste PROP, lack those receptors, have fewer fungiform papillae, and have low-intensity tastes.
PTC taste
Phenylthiocarbamide tastes bitter and is similar to propylthiouraci. One-third of people cannot taste it.
1-Consciousness-Sense-Taste-Anatomy
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Date Modified: 2022.0225