Periodic table illustrating the elements essential for life Periodic table illustrating the elements essential for life The 28 elements essential for animal life are indicated by coloured squares; trace elements are shown in yellow and those present in larger quantities are shown in green. The six most abundant elements in the human body are carbon, hydrogen, oxygen, nitrogen, phosphorus and calcium, accounting for almost 99% of the mass of an adult human. Carbon, hydrogen, oxygen and nitrogen are the building blocks of organic biomolecules, calcium is present in large amounts in bones and teeth (in addition to being vital for cell signalling in smaller amounts), phosphorus is likewise found in bones and teeth (smaller quantities are a vital part of DNA, adenoside triphosphate – the energy currency of the cell – and play an important role in cell signalling). Amanda L. Jonsson et al. Essays Biochem. 2017;61:401-427 ©2017 by Portland Press Ltd