Taste {taste, sense} {gustation} detects chemicals dissolved in water, using molecule electrochemical reactions and shape, acidity, and polarity. Taste molecules are below 200 molecular weight and include ions, hydrogen ions, hydroxide ions, and sugars. Taste is a synthetic sense, with some analysis.
physical properties
Tastable molecules include hydrogen ions, hydroxide ions, salt ions, and sugars, which are water-soluble and have molecular weights less than 200. Water-soluble molecules vary in size, shape, chemical sites, acidity, and ionicity. Water-soluble chemicals vary in concentration. Tastable molecules attach to tongue chemical receptors.
types
Taste types are sweet, salt, sour, and bitter.
Sweet is not acid, salt, or base. Salt is neutral. Sour is acid. Bitter is base.
Sweet is non-polar. Salt, sour, and bitter are polar.
Sour acid and salt are similar. Bitter base and salt are similar. Sweet and salt are similar.
Sour acid and bitter base are opposites. Sour acid and sweet are opposites. Salt and sweet are opposites.
Taste has same physical properties, and taste processes are similar, so taste perceptions are similar, for all undamaged people. Tastes relate in only one consistent and complete way. Tastes are not symmetric, so tastes have unique relations. Tastes cannot substitute. Tastes have specific sense qualities and so can never switch to other tastes. Newborns can detect sweet as pleasant and bitter as aversive.
Perhaps, the first taste was a food or poison sign.
mixing
Bitter and sweet can mix. Bitter and salt can mix. Salt and sour can mix. Tastes do not mix to make new tastes.
properties
Taste habituates quickly. Taste is in real time, with a half-second delay. Temperature affects taste, so sweets taste less sweet when warm than when cold. Taste has early, middle, and late sensations.
Sour acid and salt are similar. Bitter and salt are similar. Sweet and salt are similar.
Sour (acid) and bitter (base) are opposites. Sweet (neutral) and sour (acid) are opposites. Salt and sweet are opposites.
source location
Taste can detect source location. Taste can detect several sources from one location.
Taste has few spatial affects. However, taste can have interference from more than one source.
evolution
Perhaps, salt receptors evolved because animals need sodium and need associated chloride.
Perhaps, sour receptors evolved to detect food or dangerous acidic conditions.
Perhaps, sweet receptors evolved to detect sugar nutrients.
Perhaps, bitter receptors evolved to detect poisons.
development
Newborns do not taste salt, but babies soon can taste it, and they like it.
Newborns can taste sour. Children like sour taste.
Newborns can taste sweet and think it pleasant.
Babies can taste bitter and think it aversive.
relations to other senses
Taste and retronasal-area smell can combine to make flavor. Odors affect taste receptors. Taste has higher concentration than smell. Taste has water as solvent, not air. Taste has few spatial affects. Taste molecules can have polarization. Taste and smell can have interference from more than one source. Both taste and smell are often silent. Taste and smell have early, middle, and late sensations. Taste does not use vibrations, but smell can use vibrations.
Taste is at tongue surface and so has touch. Texture affects taste. Touch can feel solutions on tongue and react to noxious tastes. Touch locates tongue taste receptors.
Taste seems unrelated to hearing and vision.
effects
Sour makes people's lips pucker, sometimes downward.
Bitter makes people's eyes and nose change.
Salt is alerting.
Savory is less alerting.
Sweet is calming.
Taste and retronasal-area smell can combine {flavor, taste}.
Taste anatomy includes tongue, taste buds, chemical receptors, and neurons. Tongue chemical receptors send to thalamus, which sends to cortical regions.
Tongue skin has chemical receptors for water-soluble molecules {taste, anatomy}. Receptors have one receptor type. Taste uses four or five main receptor types, each with variations. Receptors have dozens of combinations. Taste buds have all receptor types. Tongue has no special salt, sweet, or sour regions.
Taste neurons typically receive from more than one taste-receptor type. Taste neurons detect one main taste category: salt-best, sugar-best, acid-best, and bitter-best. Similar taste sensations vary only in intensity, not in quality, because similar receptors go to same taste neuron.
Medulla solitary tract nucleus receives from tongue cranial nerves 7, 9, and 10, determines taste preferences, and sends to thalamus and to parabrachial nucleus, which also receives from GI tract. Taste cortex is in insula, which sends to orbitofrontal cortex.
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.
Tongue and soft-palate hemispherical cell clusters {taste bud}| hold cells {taste receptor cell} that have tip microvilli. Adult tongue has 10,000 taste buds, but babies have more. Taste buds last one week, fade, and then new ones grow.
Taste-bud cells have tips with projections {microvillus} {microvilli} that extend into taste pore.
Tongue has four bump types {papilla}| {papillae}.
Papillae {circumvallate papilla} can be largest, be before tonsils, be large circular mounds with depressed circumference, and have three to five taste buds (on tongue rear sides).
Papillae {filiform papilla} can be smallest, be most, be down top middle, and have no taste buds.
Papillae {foliate papilla} can be medium-size, be at back sides, be tissue folds at tongue rear and outsides, and have taste buds.
Papillae {fungiform papilla} can be next smallest, be on tongue broad part, be one-millimeter-size mushroom shapes at tongue tip and edges, and have six taste buds each.
Taste distinguishes water-soluble salt, sugar, acid, and base chemicals {taste, physiology}. Taste receptors are for only salt, sugar, acid, or base. For example, salt taste receptors measure salt concentration as salt-to-receptor binding per second. Different taste receptors converge on taste neurons. Similar taste sensations vary only in intensity, not in quality, because similar receptors go to same taste neuron.
Salty chemicals are small and ionic and have neutral acidity. Sodium-chloride sodium ions make pure salt taste. Potassium-chloride potassium ions make salt and bitter taste.
Sour chemicals are small, ionic, and acidic. Hydrogen chloride makes pure sour taste.
Sweet chemicals are large and polar and have neutral acidity. Glucose makes pure sweet taste. Fructose and galactose are sweet.
Bitter chemicals are small or large, ionic, and basic. Hydroxide ions make pure bitter taste.
Savory chemicals are large, ionic-polar, and slightly acidic. L-glutamic acid sodium salt (monosodium glutamate) tastes distinctively salty and sweet.
Taste neurons inhibit and excite each other to compare sugar, acid, base, salt, and L-glutamate receptor inputs to find differences and indicate taste types [Kadohisa et al., 2005] [Pritchard and Norgren, 2004] [Rolls and Scott, 2003].
Tastes are relative. For example, salt only tastes salty relative to other tastes [Brillat-Savarin, 1825]. Saliva salt level is highest in morning, drops until afternoon, and then rises again to high morning value, so salt amount needed for salt taste varies during day. Saliva substance concentrations can vary tenfold. Tongue taste-receptor pattern affects taste.
Taste is painful at high concentrations. Taste can detect low concentrations.
Taste can detect source location. Taste can detect several sources from one location.
acidity
Molecule atoms, bonds, and electric charge determine acidity, which can be acidic, neutral, or basic.
Sour is acidic. Salty is neutral acidity. Savory is neutral. Sweet is neutral. Bitter is basic.
Salty, savory, and sweet have similar neutrality.
Sour and bitter have opposite acidity.
ionicity
Molecule atoms and bonds and molecule-electron properties determine ionicity, which can be ionic or polar.
Sweet and some bitters are polar. Salty, savory, sour, and some bitters are ionic.
Sour and sweet, salty and sweet, and savory and sweet have opposite ionicity.
size
Sour and some bitters have similar small size.
Salts have medium size.
Sweet, savory, and some bitters have similar large size.
polarity or ionicity; acidity, neutrality, or basicity; and size
Taste molecules have a combination of polarity or ionicity; acidity, neutrality, or basicity; and size.
Taste molecules can be:
acidic: hydrogen ion (sour)
neutral: monosodium glutamate (savory)
neutral: sodium chloride and potassium chloride (salt)
neutral: glucose and fructose (sweet)
slightly basic: phenylthiourea, phenylthiocarbamide, and 6-n-propylthiouracil (bitter)
basic: hydroxide ion (bitter)
Taste molecules can be:
polar: glucose and fructose (sweet)
polar: phenylthiourea, phenylthiocarbamide, and 6-n-propylthiouracil (bitter)
ionic: hydroxide ion (bitter)
ionic: hydrogen ion (sour)
ionic: sodium chloride and potassium chloride (salt)
ionic: monosodium glutamate (savory)
(They cannot be non-polar, because non-polar does not dissolve in water.)
Taste molecules can have molecular weight 1 to 200:
1: hydrogen ion (sour)
17: hydroxide ion (bitter)
58: sodium chloride (salt)
75: potassium chloride (salt)
152: phenylthiourea and phenylthiocarbamide (bitter)
169: monosodium glutamate (savory)
170: 6-n-propylthiouracil (bitter)
180: glucose and fructose (sweet)
Taste molecules are:
Sour: acidic, ionic, and small.
Salt: neutral, ionic, and medium.
Savory: neutral, ionic, and large.
Sweet: neutral, polar, and large.
Bitter: slightly basic, polar, and large.
Bitter: basic, ionic, and small.
Acidic and polar do not exist, because acids are ionic. Basic and polar do not exist, because bases are ionic.
Small and polar do not exist, because small molecules are ionic. Medium and polar do not exist, because medium molecules are ionic.
Small and neutral do not exist, because small molecules have hydrogen ions or hydroxide ions. Large and acidic do not exist, because acidic molecules have small hydrogen ions. Large and basic do not exist, because basic molecules have small hydroxide ions.
Taste molecules fall into six categories:
Large polar: neutral (sweet) or slightly basic (bitter)
Large ionic: neutral (savory)
Medium ionic: neutral (salt)
Small ionic: acidic (sour) or basic (bitter).
If new flavor associates with gastrointestinal illness, people are averse to the flavor {learned taste aversion}.
Taste receptors adjust for current saliva substance concentrations. Taste stimulus at same concentration as saliva concentration is tasteless {taste zero}.
Henning said tastes are bitter, salty, sour, and sweet {primary taste} {basic taste}. Some people can distinguish monosodium glutamate savory taste from salt taste.
Peppers have molecules {capsaicin} that cause pain and sweating.
Ethiopian spice mixtures {chow, spice} have chili and other spices and inhibit bacteria.
Roots {ginger, taste} prevent seasickness.
Brazilian daisy {spilanthes} {jambu} numbs and tingles mouth.
Some people can distinguish umami savory taste from salt taste. Glutamic-amino-acid sodium salt {monosodium glutamate}| (MSG) tastes distinctively salty and sweet. Autolyzed yeast extract, glutavene, calcium caseinate, sodium caseinate, Marmite, soy sauce, anchovy, and fish sauce have high MSG.
Brain makes amphetamines {phenylethylamine} (PEA).
For one-half to two-thirds of people, with dominant allele, urea compounds {phenylthiourea} (PTU) can taste bitter. PTU has no taste to other one-half to one-third of people, who cannot recognize NC=S chemical functional group [Kalmus and Hubbard, 1960].
Puffer-fish tissues can have poison {tetrodotoxin}, to which predators are averse.
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Date Modified: 2022.0225