Explain the significance of sodium,potassium,magnesium,and calcium in biological fluids.

(N/A) Sodium $(Na)$: Sodium ions are found primarily in the blood plasma and in the interstitial fluids surrounding the cells.
Uses: $(i)$ Sodium ions help in the transmission of nerve signals. $(ii)$ They help in regulating the flow of water across the cell membranes. $(iii)$ They also help in transporting sugars and amino acids into the cells.
$(b)$ Potassium $(K)$: Potassium ions are found in the highest quantity within the cell fluids.
Uses: $(i)$ $K^+$ ions help in activating many enzymes. $(ii)$ They participate in oxidizing glucose to produce $ATP$. $(iii)$ They also help in transmitting nerve signals.
$(c)$ Magnesium $(Mg)$: Magnesium is a macro-mineral,indicating its high abundance in the human body.
Uses: $(i)$ $Mg^{2+}$ helps in relaxing nerves and muscles. $(ii)$ $Mg^{2+}$ helps in building and strengthening bones. $(iii)$ $Mg^{2+}$ maintains normal blood circulation.
$(d)$ Calcium $(Ca)$: Calcium is a macro-mineral.
Uses: $(i)$ $Ca^{2+}$ helps in the coagulation of blood. $(ii)$ $Ca^{2+}$ helps in maintaining homeostasis and muscle contraction.