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Taste Receptor Cells
Taste
cells are transformed epithelial cells that reside in
taste buds in the papillae of the tongue, palate, pharynx,
epiglottis, and esophagus
 Circumvallate Papillae
 Fungiform papillae
 Filliform papillae
Saliva contacts the microvilli through the taste pore
The solubility of a substance affects the response time
Salty
 EnAC Sodium Channel
 NaCl – Ion channel allows Na⁺ to enter the cell
 Depolarization occurs and voltage-gated Ca²⁺ channels open
 Ultimately leads to neurotransmitter release
Sour
EnAC protein
H⁺ blocks K⁺ channels increasing intracellular [K⁺] via the MDEG1 receptor
H⁺ also binds to yet another protein which allows Na⁺ ions to flow down the
concentration gradient into the cell
Bitter
G protein coupled receptor (GCPR) - gustducin
Activated phosphodiesterase leads to conversion of cAMP to AMP
cAMP holds K⁺ ions open – so intracellular K⁺ concentration ↑
Sweet
GPCRs coupled with gustducin
Adenylate cyclase becomes active increasing [cAMP]
Ca²⁺ channels open inreasing intracellular [Ca²⁺]
K⁺ channels close
Umami (Savory)
Similar to the bitter and sweet pathways
L-glutamate binds to mGluR4 (a GPCR)
mGluR4 is thought to close a cation channel which
causes depolarization
Fats?
Spicy … ???
Spicy is not a taste receptor cell
Temperature sensitive receptors respond to spicy foods
Tactile receptors also present information about a
substance’s texture
Drosophila melanogaster has taste bristles containing gustatory
receptor neurons at the end of the proboscis as well as on the legs
and anterior wing margins
Internal taste organs line the walls of the pharynx
Sensation of harmful substances
regurgitate response
Sensation of pleasurable substances
sucking reflexes
So why do different people have different food
preferences?