Sentence:  A few types of molecules get sensed by receptors on the tongue. Protons coming off of acids ping receptors for "sour." Sugars get received as "sweet." <WSD>Bitter</WSD>, salty, and the proteinaceous flavor umami all set off their own neural cascades. 
Meaning of the word marked with <WSD> tags:  Having an acrid taste (usually from a basic substance).