Classification of essential elements based on the function they perform is as follows:

1.Essential elements as components of energy related compounds

For example Magnesium in Chlorophyll and Phosphorus in ATP molecule.

2.Essential elements as components of Structural elements of cells

For example Hydrogen bonds are seen in secondary structure of proteins,Carbon and Oxygen in proteins,lipids,carbohydrates and nucleic acids.

3.Essential elements as Activator and Inhibitor of enzymes:

For example Magnesium (Mg²⁺) is an activator of both Ribulose Bisphosphate and Phosphoenol pyruvate enzyme which are involved in photosynthetic carbon fixation.

4.Essential elements which can alter osmotic pressure:

For example Potassium plays an important role in opening and closing of Stomata.