పులుపు: కూర్పుల మధ్య తేడాలు
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K.Venkataramana (చర్చ | రచనలు) |
K.Venkataramana (చర్చ | రచనలు) |
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పంక్తి 4:
==శాస్త్ర పరంగా==
{{Wiktionary|sour}}
Sourness is the taste that detects [[acid]]ity. The sourness of substances is rated relative to dilute [[hydrochloric acid]], which has a sourness index of 1. By comparison, [[tartaric acid]] has a sourness index of 0.7, [[citric acid]] an index of 0.46, and [[carbonic acid]] an index of 0.06.<ref name="textbookofmedicalphysiology8thed">Guyton, Arthur C. (1991) ''Textbook of Medical Physiology''. (8th ed). Philadelphia: W.B. Saunders</ref><<ref name="McLaughlin&Margolskee1994">{{citation |date=November–December 1994 |author=McLaughlin, Susan, & Margolskee, Rorbert F |title=The Sense of Taste [[American Scientist]] |volume=82 |issue=6 |pages=538–545}}</ref>
Sour taste is detected by a small subset of cells that are distributed across all taste buds in the tongue. Sour taste cells can be identified by expression of the protein PKD2L1,<ref>{{cite web|url=http://www.sciencedaily.com/releases/2006/08/060823184824.htm|title=Biologists Discover How We Detect Sour Taste |publisher=Sciencedaily.com |date=2006-08-24 |accessdate=2012-08-04}}</ref>although this gene is not required for sour responses. There is evidence that the protons that are abundant in sour substances can directly enter the sour taste cells. This transfer of positive charge into the cell can itself trigger an electrical response. It has also been proposed that weak acids such as acetic acid, which are not fully dissociated at physiological pH values, can penetrate taste cells and thereby elicit an electrical response. According to this mechanism, intracellular hydrogen ions inhibit potassium channels, which normally function to hyperpolarize the cell. By a combination of direct intake of hydrogen ions (which itself depolarizes the cell) and the inhibition of the hyperpolarizing channel, sourness causes the taste cell to fire action potentials and release neurotransmitter.
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