Inorganic ions in animals and plants are ions necessary for vital cellular activity. They contribute to osmotic pressure of body fluids as well as performing a number of other important functions. Below is a list of some of the most important ions for living things as well as examples of their functions.

Ca²⁺, Calcium is a component of bones and teeth. It is also functions as a biological messenger, as do most of the ions listed below. See Calcium deficiency

K¹⁺, Pottasium ions' main function in animals is osmostic balance, particuarly in the kidneys. See Potassium deficiency.

Na¹⁺, Sodium ions have a similar role to potassium ions. See Sodium deficiency.

Mg²⁺, Most importantly, magnesium ions are a component of chlorophyll. See Magnesium deficiency

Cl^1-, Inability to transport chloride ions in humans manifests itself as Cystic fibrosis

CO₃^2-, The shells of sea creatures are calcium carbonate. In blood approximately 85% of carbon dioxide, is converted into aqueous carbonate ions (an acidic solution), allowing a greater rate of transportation.

PO₄^3-, Adenosine triphosphate is a common molecule which stores energy in an accessible form. Bone is calcium phosphate.

Fe^2/3+. Haemoglobin, the main oxygen carrying molecule has a central iron ion.