For ions in inorganic compounds see ionic compounds.
Inorganic ions in animals and plants are ions necessary for vital cellular activity. In body tissues, ions are also known as electrolytes, essential for the electrical activity needed to support muscle contractions and neuron activation. 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 also functions as a biological messenger, as do most of the ions listed below. See Hypocalcaemia
• K⁺, Potassium ions' main function in animals is osmotic balance, particularly in the kidneys. See Hypokalemia.
• Na⁺, 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^-, 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.
• NO₃^-, source of nitrogen in plants for the synthesis of proteins.