For 10 points, name this element with atomic number 19 and chemical symbol K.
One type of protein named after this element has a voltage-gated type that causes the falling phase of the action potential, and is this element's namesake "channel." A cellular exchange between this element and another is motivated by an enzyme that is a "pump" for this element and sodium, while high quantities of this element are ingested upon drinking orange juice and eating bananas. For 10 points, name this element with atomic number 19 and chemical symbol K.
One type of protein named after this element has a voltage-gated type that causes the falling phase of the action potential, and is this element's namesake "channel.
potassium