Alkali metals biological functions

Not all complexes are purely electrostatic. In fact, many metal complexes in biological systems have covalent interactions as well. In these cases, the ligand donates a pair of electrons (acting as a Lewis base) to the metal, which functions as a Lewis acid. Therefore, metals can be evaluated based on their abilities to accept electron pairs. Alkali metal ions (Na+, K+) and alkaline earth metals (Mg2+, Ca2+) tend to not form stable complexes with Lewis base ligands. Transition metal ions, particularly those with vacant ri-orbitals, will form more stable complexes with Lewis base-acting ligands. 

The alkali metal ions are very important for the proper functioning of biological systems, such as nerves and muscles Na+ and K+ ions are present in all body cells and fluids. In human blood plasma the concentrations are... 

Sodium and potassium are the most abundant alkali metals. Many biological functions are controlled by sodium and potassium ions. 

Appropriate sodium ion levels (along with potassium levels) are essential for proper cell function in biological systems, see also Alkali Metals. 

Alkali metal ions are involved in numerous important biological processes, such as transmission of nerve impulses, nervous control of secretion and muscle functions, protein synthesis, and enzymatic regeneration of metabolism. Crown compounds, being complex formers, are naturally apt to interfere in such processes. For instance, it was found that lipophilic cryptands of structural formula... 

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