anions

• nitrate 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).
• hydrogencarbonate ions act as a buffer, which helps to maintain the pH of the blood.
• chloride ions are involved in the 'chloride shift' which helps to maintain the pH of the blood during gas exchange. Acts as a cofactor for the enzyme amylase. Also involved in some nerve impulses.
• phoshate ions are involved in photosynthesis and respiration reactions. Needed for the synthesis of many biological molecules, such as nucleotides (including ATP), phospholipids, and calcium phosphate (which strengthens bones).
• Hydroxide ions affect the pH of substances (more OH- ions than H+ ions in a solution creates an alkali).