Final answer:
Calcium plays crucial roles in the body including in neuromuscular excitability, structural integrity of bones and teeth, and blood clotting. The correct functions of Calcium (Ca2+) from the provided options are 1, 4, and 5.
Step-by-step explanation:
The important functions of Calcium (Ca2+) include neuromuscular excitability, which is essential for the function of nerves and the contractility of both cardiac and skeletal muscle. Calcium also provides the structural integrity of bone & teeth, being a critical component of hydroxyapatite, which gives hardness to these tissues. Moreover, it plays a vital role in the clotting of blood by helping in the transformation of prothrombin into thrombin and is involved in intracellular signaling pathways as a second messenger.
Considering the options provided and the functions mentioned, the correct answer would be d) 1, 4, 5 which comprises neuromuscular excitability, structural integrity of bone & teeth, and clotting of blood.