Q.Name the following.
Ions having high concentration in cell sap.

Sodium and potassium ions are the principal electrolytes that maintain the electrochemical and osmotic balance of body fluids. $Na^+$ is concentrated mainly outside cells and, together with $Cl^-$ and $HCO_3^-$, regulates extracellular fluid volume, acid–base balance and blood pressure, and is central to the transmission of nerve impulses via the sodium–potassium pump; $K^+$, concentrated mainly inside cells, activates several enzymes involved in carbohydrate metabolism (oxidation of glucose to generate ATP) and, like $Na^+$, is essential for nerve-impulse conduction and muscle contraction. Magnesium and calcium play different but equally essential roles: $Mg^{2+}$ is the central metal ion of chlorophyll in plants and, in animals, activates numerous enzymes including those of the glycolytic and phosphate-transfer pathways, while $Ca^{2+}$ is the chief structural comp …