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 to mainly transport this element. Paralytic shellfish poisoning occurs when alkaloids like saxitoxin block the transport of this element. A symporter of glucose (10[1])and this element (10[1])called SGLT2 is found in proximal tubules. Subunits of proteins that conduct this element (-5[1])contain six transmembrane passes and are voltage-gated. An ion of this element enters neurons during action (10[1])potential (-5[1])firing. (10[1])Blockers for this element’s channels can be used to treat arrhythmia. Hydrolysis of ATP pumps three atoms of this element out of cells against potassium. (10[3])For 10 points, (10[1])name this element (10[1])found alongside (10[1])chloride in table salt. ■END■