||"...This binding/buffering is even more pronounced in the intracellular compartment. For H+, the buffer capacity ß is defined as (Roos & Boron 1981) ß=?B/?pH, (eq.1) where B is the amount of strong base that is needed to produce a given change in pH. ß˜50mmole/(LXpH). The intracellular fluid is well buffered. In the case of Ca2+ (and Mg2+), the buffering is described using the ion-binding ratio, kS, defined as
(primary source) kS=?(total [Ion2+])/?(free [Ion2+]) (eq.2) for Ca2+, kS˜100, for Mg2+, kS˜20. The low
intracellular [Ca2+], [Ca2+]i, in particular means that Ca2+ becomes an important intracellular messenger
because the transmembrane Ca2+ fluxes are large enough to cause measurable changes in [Ca2+]i."