Inorganic ions: iron, hydrogen, sodium and phosphate

In a nutshell

Inorganic ions play a key role in many biological processes. They are especially important for haemoglobin, enzymes, co-transport, ATP and nucleotides.

Inorganic ions

Definition

Ions are atoms or a group of atoms that have an electric charge.

Positively charged ions are known as cations and negatively charged ions are called anions. Inorganic ions do not contain any carbon and they can be found in solution, in cells cytoplasms and in body fluids of organisms. The properties of the inorganic ions determine their specific role. There are four inorganic ions you need to know about: iron ions, hydrogen ions, sodium ions and phosphate ions.

Iron ions

Haemoglobin is a protein made up of four polypeptide chains each with an iron ion ( $Fe^{2+}$ ) in the centre. It is the iron ion that binds the oxygen. When $Fe^{2+}$ binds oxygen it becomes $Fe^{3+}$ until the oxygen is released.

Hydrogen ions

Hydrogen ions ( $H^+$ ) determine pH as pH is calculated using the concentration of $H^+$ in the environment. More hydrogen ions mean the lower the pH and the more acidic the environment. pH is important for enzyme-controlled reactions as enzymes can be denatured at extreme pHs.

Sodium ions

Sodium ions ( $Na^+$ ) are involved in transport across membranes. Large molecules such as glucose and amino acids are transported across cell-surface membranes alongside a sodium ion. This is known as co-transport.

Phosphate ions

Phosphate ions ( $PO_4\space ^{3-}$ ) are key components in DNA, RNA and ATP. The phosphate ions are known as phosphate groups when attached to another molecule and the bonds between phosphate groups are what store energy in ATP. In DNA and RNA the phosphate groups allow nucleotides to join up.