A trace element is a chemical element of a minute quantity, a trace amount, especially used in referring to a micronutrient,<ref name="Bhattacharya">Template:Cite journal</ref><ref name="MW1">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> but is also used to refer to minor elements in the composition of a rock, or other chemical substance.
In nutrition, trace elements are classified into two groups: essential trace elements, and non-essential trace elements. Essential trace elements are needed for many physiological and biochemical processes in both plants and animals. Not only do trace elements play a role in biological processes but they also serve as catalysts to engage in redox – oxidation and reduction mechanisms.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Trace elements of some heavy metals have a biological role as essential micronutrients.
TypesEdit
{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} The two types of trace element in biochemistry are classed as essential or non-essential.
Essential trace elementsEdit
An essential trace element is a dietary element, a mineral that is only needed in minute quantities for the proper growth, development, and physiology of the organism.<ref>Template:Cite book</ref> The essential trace elements are those that are required to perform vital metabolic activities in organisms.<ref name="Soto-Jiménez M.F.">Template:Cite journal</ref> Essential trace elements in human nutrition, and other animals include iron (Fe) (hemoglobin), copper (Cu) (respiratory pigments), cobalt (Co) (Vitamin B12), iodine (I), manganese (Mn), chlorine (Cl), molybdenum (Mo), selenium (Se) and zinc (Zn) (enzymes).<ref name="Soto-Jiménez M.F." /><ref>Template:Cite book</ref> Although they are essential, they become toxic at high concentrations.<ref name="Jomova">Template:Cite journal</ref>
Non-essential trace elementsEdit
Non-essential trace elements include silver (Ag), cadmium (Cd), mercury (Hg), and lead (Pb). They have no known biological function in mammals, with toxic effects even at low concentration.<ref name="Soto-Jiménez M.F." />
The structural components of cells and tissues that are required in the diet in gram quantities daily are known as bulk elements.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>