In terms of serum concentration, where is calcium (Ca) most abundant compared to magnesium (Mg)?

Calcium (Ca) plays a crucial role in various physiological processes, including muscle contraction, nerve function, and blood coagulation. In terms of serum concentration, calcium is indeed more abundant compared to magnesium.

In the extracellular space, calcium is typically maintained at higher concentrations, approximately 1-2 mM in the serum, while magnesium levels are lower, around 0.7-1.0 mM. This greater abundance of calcium is critical for its functions outside the cells, such as in signaling pathways and cellular interactions.

While both minerals are present in the intracellular environment, magnesium is generally more concentrated within cells compared to calcium. Therefore, in terms of the serum concentration, option C accurately reflects calcium as being greater in serum concentration than magnesium, highlighting its significant role in extracellular functions.