cations

• The calcium ion is involved in the transmission of nerve impulses and the release of insulin from the pancreas. Acts as a cofactor for many enzymes, e.g. those involved in blood clotting. Is important for bone formation.
• Sodium ions are important for generating nerve impulses, for muscle contraction and for regulating fluid balance in the body.
• potassium ions are important for generating nerve impulses, for muscle contraction and for regulating fluid balance in the body. Activates essential enzymes needed for photosynthesis in plant cells.
• hydrogen ions affect the pH of substances. Also important for photosynthesis reactions that occur in the thylakoid membranes inside chloroplasts and respiration reactions that occur in the inner membrane of mitochondria.
• ammonium ions are absorbed from the soil by plants and is an important source of nitrogen (which is then used to make, e.g. amino acids, nucleic acids).