8. Trace elements
Summary
- Many minerals are needed by the body in small doses
Iron
Iron is essential for all living organisms. We require 1-3 mg of iron every day. Iron is absorbed as Fe2+ ions but is stored as Fe3+. Many proteins contain iron in humans. They can be divided into two groups: the ones that require iron as part of the heme group, and the ones that don’t contain heme. Most proteins belong to the first group, like haemoglobin, myoglobin, cytochromes, catalase, NO synthase, and more. Only a few proteins belong to the second group, like transferrin and ferritin.
Copper
Copper is transported in the blood by ceruloplasmin and albumin. It’s needed for redoxenzymes, like complex IV of the respiratory chain, superoxide dismutase and hydroxylases.
Zinc
Zinc is important for DNA and RNA polymerases, zinc finger structures, alcohol dehydrogenase, proteases, carbonic anhydrase and for olfaction. It’s also important in Thr-tRNA synthetase.
The rest
Cr3+ may be a part of glucose tolerance factor, which might play a role in glucose uptake (we’re not sure). Cr4+ is toxic however.
Manganese is a cofactor in enzymes like xanthine oxidase, arginase, pyruvate carboxylase, PP2A, and several other hydroxylases. It’s also a component of glycogenin.
Molybdenum is a cofactor in xanthine oxidase. It’s also important in nitrogen fixation in bacteria.
Cadmium and mercury are heavy metals that bind to -SH groups on proteins. By doing this they can inhibit certain important enzymes, like acetylcholinesterase, which make them deadly.
Aluminium is not necessary and isn’t absorbed in any considerable amounts. Al(OH)3 is used as an antacid.
Lead inhibits the first reaction of heme synthesis, disturbing any protein and cell dependant on this group.
Arsenate inhibits both the pyruvate dehydrogenase and α-ketoglutarate dehydrogenase complexes.
Selenium is an important component of selenocysteine, an amino acid based on cysteine that is used to build up selenoproteins, like glutathione peroxidase and deiodinases. It is also found in muscle and sperm.
Fluoride prevents dental caries and is best absorbed from water.
Iodide is essential for the thyroid gland to produce thyroid hormones. Iodide deficiency leads do an enlarged thyroid, called goiter.