Organs and tissues

Different tissues contain Ca in diffent concentrations. In vertebrates Ca (in a form of CaSO₄) is the most importaint (and specyfic) compound of bones.

Some invertebrates use Ca for building their outer (radiolaria) or inner sceleton.

There are also some plants which accumulate Ca in their tissues, thus making them more firm.

In cell biology Ca2+ ions are one of the most widespread messengers, their entrance into cytoplasm (either from outer space through cell membrane or from some internal Ca storages) represent the most importaint sighan for the whole cell machinery. Ca2+ entering the cell cause the specific action of this cell, whatever this action is: secretory cells release vesicules sith their secretion, muscle cells contract, synapses go into processes of synaptic plasticity etc.

The same Ca2+ ions can, however, bring damage to cells if there are too many of them (for example in a case of overexitation in neural circuits). This may even cause cell apoptosis.

See also: Ca-binding proteins