For 10 points, name this essential mineral that is stored in bones and teeth, symbolized Ca+2.
In fertilization, the release of this ion following the fusion of the gamete membranes triggers the cortical reaction, which blocks against polyspermy. Along with cyclic AMP, this ion is a common secondary messenger in cells. Inositol triphosphate, or IP3, causes the release of this ion from the smooth ER, and the release of (*) parathyroid hormone activates vitamin D, which triggers the reuptake of this ion in the intestines. The release of this ion triggers muscle contraction, and a deficiency of it can lead to osteoporosis. For 10 points, name this essential mineral that is stored in bones and teeth, symbolized Ca+2.
In fertilization, the release of this ion following the fusion of the gamete membranes triggers the cortical reaction, which blocks against polyspermy.
 calcium (accept Ca+2 before end of question)