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2.1 Chemical Elements and Water • The three commonest chemical elements of life are carbon, hydrogen and oxygen. They are part of all the main organic compounds in living organisms. • Other elements are also needed by living organisms including nitrogen, calcium, phosphorus, iron and sodium. • Element Role in plants or animals Nitrogen Part of the amine groups of amino acids and therefore proteins. Calcium Needed to male the mineral tat strengthens bones and teeth. Phosphorus Part of the phosphate groups in ATP and DNA molecules. Iron Needed to make hemoglobin and thus to carry oxygen in blood Sodium Used in neurons (nerve cells) for the transmission of nerve impulses. • An atom is a single particle of a chemical element. It has uncharged particles. An ion is an atom that either gains or loses electrons.
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