▁of ▁its ▁many ▁spectral ▁lines ▁and ▁the ▁a for ement ioned ▁reasons . ▁ ▁Bi ological ▁role ▁Many ▁period ▁ 4 ▁elements ▁find ▁roles ▁in ▁cont rolling ▁protein ▁function ▁as ▁secondary ▁mess engers , ▁struct ural ▁components , ▁or ▁en zym e ▁c of act ors . ▁A ▁gradient ▁of ▁pot ass ium ▁is ▁used ▁by ▁cells ▁to ▁maintain ▁a ▁memb rane ▁potential ▁which ▁enables ▁ne uro trans mit ter ▁firing ▁and ▁facil itated ▁diffusion ▁among ▁other ▁processes . ▁Cal ci um ▁is ▁a ▁common ▁signal ing ▁mole c ule ▁for ▁prote ins ▁such ▁as ▁cal mod ul in ▁and ▁plays ▁a ▁critical ▁role ▁in ▁trigger ing ▁ske let al ▁mus cle ▁contra ction ▁in ▁verte br ates . ▁S elenium ▁is ▁a ▁component ▁of ▁the ▁non can on ical ▁am ino ▁acid , ▁s elen oc yst e ine ; ▁prote ins ▁which ▁contain ▁s elen oc yst e ine ▁are ▁known ▁as ▁s elen op rote ins . ▁Mang an ese ▁en zym es ▁are ▁util ized ▁by ▁both ▁e uk ary otes ▁and ▁pro k ary otes , ▁and ▁may ▁play ▁a ▁role ▁in ▁the ▁vir ul ence ▁of ▁some ▁path ogen ic ▁b acter ia . ▁Van ab ins , ▁also ▁known ▁as ▁van ad ium - associ ated ▁prote ins , ▁are ▁found ▁in ▁the ▁blood ▁cells ▁of ▁some ▁species ▁of ▁sea ▁squ ir ts . ▁The ▁role ▁of ▁these ▁prote ins ▁is ▁disput ed , ▁although ▁there ▁is ▁some ▁spec ulation ▁that ▁they ▁function ▁as ▁o xygen