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 and this element called SGLT2 is found in proximal tubules. Subunits of proteins that conduct this element contain six transmembrane passes and are voltage-gated. (-5[1])An (-5[1])ion of this (-5[1])element (10[1])enters neurons during action potential (10[2])firing. 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. For 10 (10[1])points, name this element (10[1])found alongside chloride in table salt. ■END■ (10[1])