Charged particles in living systems
An atom or group of atoms carrying an overall electrical charge is an ion. A positive ion is termed a cation, while a negative ion is an anion.
The term inorganic ion is used here for an ion whose composition contains no carbon.
Within organisms, these ions are dissolved in the cytoplasm and in body fluids. Their abundance is not uniform: some occur at comparatively high concentrations, whereas others are present at very low concentrations.
Different ions perform different functions because their properties differ. Changes in the concentration of certain ions can also contribute to cell signalling and neuronal transmission.
| Ion | Key biological context |
|---|---|
| H+ | pH and conditions for enzyme-controlled reactions |
| Fe2+ / Fe3+ | Iron ions, including Fe2+ in haemoglobin |
| Na+ | Co-transport and transmission of nerve impulses |
| PO43− | Phosphate groups in molecules including DNA and ATP |