The minerals can be found in living things in three ways:
Precipitated mineral salts constitute solid, insoluble structures with skeletal function. For instance:
- Calcium carbonate in the shells of mollusks, crustaceans, corals and vertebrates.
- Calcium phosphate, Ca3 (PO4)2, which, together with calcium carbonate, which, deposited on collagen, constitute bones.
- Silica (SiO2) in the exoskeletons of diatoms and grasses, etc.
The dissolved mineral salts are dissociated into ions:
- Cations: Na+, K+, Ca2+ and Mg2+.
- Anions: Cl-, SO42-, PO42-, HCO3-, CO32- and NO3-.