Calcium makes up between 1.5 – 2 per cent of body weight accounting for 1200 – 1600 g of the typical adult male body.
Bones and teeth contain more than 99 percent of the body’s calcium. This mineral makes bines hard and storing, able to with stand tremendous force without breaking – most of the time.
Bone also serves as a reservoir of calcium that can be drawn upon when serum calcium concentration decline.
Although less than 1 percent of body calcium is in blood and soft tissues, it plays many equally crucial roles in such vital functions as muscle contraction, nerve impulse transmission, blood clotting and cell metabolism.
When a tissue has been injured by cut, the enzymes thromboplastin is released from affected cells or blood platelets. This catalyses the conversion of the protein prothrombin into thrombin, process that requires the presence of calcium ions. Thrombin then convert fibrinogen to form fibrin, a fibrous protein.
In the contraction of muscle cells: the binding of Ca-troponin C triggers the contraction, while at the same time, Ca-calmodulin binding makes energy available .
Calcium may play a role in energy regulation and risk of obesity. Dietary calcium regulation of circulating 1,25 (OH)2D3 in turn regulates the concentration of calcium in adipocytes.
When adipocytes intracellular calcium concentration increases, this promotes the expression of lipogenic genes, and fat breakdown is reduced leading to accumulations of lipid in adipocytes.
Through this pathway, low calcium diets appear to promote fat deposition, whereas high calcium intakes afford some protection from obesity.
In the blood half the calcium exist in the form of free dissolved calcium ions, about 40 percent is loosely bound to protein molecules and the remaining 7-10 per cent is within low-molecular weight ionic compounds such as calcium citrate and calcium phosphate.
Not surprisingly, elaborate and highly complex mechanism are involved in maintaining it level within narrow limits in the cell.
Calcium homeostasis is complex because it involves the gastrointestinal tract, kidney, and bones.
Functions of calcium
