Metal ions are essential to the function of many proteins present in living organisms, such as
metalloproteins and enzymes that require metal ions as
cofactors. Processes including oxygen transport and DNA replication are carried out using enzymes such as
DNA polymerase, which in humans requires magnesium and zinc to function properly. Other biomolecules also contain metal ions in their structure, such as iodine in human thyroid hormones. The uses of some of them are listed below. The list is not exhaustive, because it covers only the principal class members; others that are
trace metals of especially low bioconcentration are not explored herein. Some elements that are
nonmetals or
metalloids (such as
selenium) are beyond the scope of this article.
Calcium Calcium is the most abundant metal in the eukaryotes and by extension humans. The body is made up of approximate 1.5% calcium and this abundance is reflected in its lack of redox toxicity and its participation in the structure stability of membranes and other biomolecules. Calcium plays a part in
fertilization of an egg, controls several developmental process and may regulate cellular processes like
metabolism or learning. Calcium also plays a part in
bone structure as the rigidity of vertebrae bone matrices are akin to the nature of the
calcium hydroxyapatite. Even small changes in the concentration of magnesium in plant cytosol or
chloroplasts can drastically affect the key enzymes present in the chloroplasts. It is most commonly used as a
co-factor in
eukaryotes and functions as an important functional key in enzymes like
RNA Polymerase and
ATPase. In
prokaryotes, zinc can function as an
antimicrobial, zinc oxide nano-particles can function as an
antibacterial or antibiotic. Zinc
homeostasis is highly controlled to allow for its benefits without risk of death via its high toxicity. It has also been shown that sodium affects immune response both in efficiency and speed. Macrophages have increased proliferation rates at high-salt concentrations and the body uses high-sodium concentrations in isolated regions to generate an heightened immune response which fades after the infection has been dealt with.
Potassium In plants, potassium plays a key role in maintaining plant health. High concentrations of potassium in plants play a key role in synthesis of essential proteins in plants as well as development of plant organelles like cell walls to prevent damage from viruses and insects. It also lowers the concentration of low molecular weight molecules like sugars and amino acids and increases the concentration of high weight molecular weight molecules like protein which also prevent the development and propagation of viruses.
Iron Iron is also the most abundant
transition metal in the human body and it is used in various processes like oxygen transport and ATP production. It plays a key role in the function of enzymes like
cytochrome a,
b and
c as well as
iron-sulfur complexes which play an important role in ATP production. It is present in every type of cell in the brain as the brain itself has a very high energy requirement and by extension a very high iron requirement. Hemoglobin in the blood transports oxygen from the lungs to myoglobin in tissues. Both proteins are
tetramer complexes with iron protein complexes called
hemes built into each
subunit of the tetramer. The oxygen binds to the iron in the heme via
affinity-based binding or liganding and dissociates from the protein once it has reached its destination. The second being the bolstering of the growth of
neoplastic cells by suppressing host defenses. Excessive iron inhibits the activity of
CD4 lymphocytes and suppresses the
tumoricidal activity of
macrophages. The third way it can act as a carcinogen is by functioning as an essential nutrient for unrestricted proliferation of tumor cells.
Lithium Lithium is present in biological systems in
trace amounts; its functions are uncertain. Lithium salts have proven to be useful as a
mood stabilizer and
antidepressant in the treatment of mental illness such as
bipolar disorder. == Non-natural biometal complexes ==