In quinoa, class-1 HKT proteins load this element into bladder cells. Variations in hydrogen concentration in the brain cause acid-sensing pH sensor proteins (-5[1])to mainly transport this element. Paralytic shellfish poisoning occurs when alkaloids like saxitoxin block the transport of this element. (-5[2])A symporter of glucose (10[1])and this element called SGLT2 (10[1])is found in proximal tubules. Subunits of proteins that conduct this element contain six transmembrane passes and are voltage-gated. An ion of this element enters neurons during action potential firing. (10[1]-5[1])Blockers (10[2])for this element’s channels can (-5[1])be used to treat arrhythmia. Hydrolysis of ATP pumps three atoms of this element (-5[1])out of cells against potassium. (-5[1])For 10 points, name this element found alongside chloride in table salt. ■END■ (10[6]0[1])