Calcium and Phosphorus Calcium and phosphorus are predominantly localized in bone, but both elements occur in the cell,8 phosphorus being particularly important. Inorganic phosphate is the chief anion in the intracellular fluid, and the organic phosphates of the cell appear to have considerable significance in the metabolism of fats and carbohydrates, the energetics of cellular activity and the physiology of muscular contraction. The extracellular water content of calcium and phosphorus is small in absolute amounts, but it is vital in the maintenance of normal neuromuscular irritability and bone structure. In addition, both substances play a role in acid–base regulation of . . .