Core ConceptsThis article discusses the essential roles that metals play in biology, including structural framework and catalytic capabilities. You will learn some common metals and the biochemical reactions they take part in.Biological Roles of Essential ElementsMetals serve several important roles in the cell, including mediating redox reactions, balancing and transporting charge, and providing structural frameworks. We will learn about some of the molecules and processes that metals are involved in within the cell. The seven most important metals in biology are Iron, Copper Zinc, Magnesium, Calcium, Manganese, and Cobalt. Metals are important chemical constituents because they can adopt a variety of redox states and coordination environments. Many biochemical processes rely on this chemical flexibility to function.Iron (Fe)Iron is most commonly recognized in the world of biology for its role in hemoglobin. Hemoglobin is in red blood cells and is responsible for transporting oxygen. The iron located in the heme group has the ability to bind to oxygen molecules in a reversible manner. Iron is also necessary for different enzymatic reactions, especially those that occur within the mitochondria.Hemoglobin StructureCopper (Cu)Copper has the ability to switch between +1 and +2 oxidation states, allowing for it to be a useful element in electron transfer reactions. The enzyme in the mitochondrial electron transport chain, cytochrome c oxidase, is copper containing. The copper is necessary for the enzyme’s function in transferring electrons and reducing oxygen to water. Iron metabolism and connective tissue formation also involve copper. Additionally, copper plays a structural role in some proteins, adding to its versatility in biological functions.Zinc (Zn)Zinc is crucial in DNA synthesis, protein synthesis, and cell division. It provides structural integrity to various proteins and regulates gene expression.DNA polymerases, which are enzymes responsible for DNA replication and repair, are dependent on the presence of zinc for structural configuration and catalytic activity. Without zinc, they wouldn’t be able to synthesize or repair DNA properly. There are also RNA polymerases needed for transcribing DNA into RNA that have a dependency on zinc for structural and functional reasons.The synthesis of methionine, an essential amino acid, involves methionine synthase. This enzyme depends on zinc for structural stability and catalytic activity. Zinc stabilizes the active site of the enzyme, allowing it to catalyze the conversion of homocysteine to methionine.Zinc finger proteins contain zinc finger motifs, defined as small structures stabilized by zinc ions. These zinc fingers then bind to proteins, having a direct impact on cellular processes such as gene expression and signaling pathways. For example, the transcription of specific genes by binding to their promoter regions can occur by transcription factors with zinc finger motifs.The classic zinc finger motif with two histidines and two cysteines binding to the zinc ion.Magnesium (Mg)Magnesium commonly acts as a cofactor, a substance essential for an enzyme to function. It can stabilize both DNA and RNA by neutralizing their negative charges. This prevents them from repelling one another. Magnesium is also needed for ATP stability and function, as it binds to ATP and facilitates interactions with other enzymes.Calcium (Ca)Calcium is a metal needed for bone and teeth formation. It acts as a secondary messenger in pathways that include regulation of cellular responses, such as muscle contraction and neurotransmitter release. Calcium ions can bind to proteins, thus changing their shape and activating or inhibiting different cellular processes.Manganese (Mn)Manganese is a trace metal in biology, playing a role in bone formation, metabolism of amino acids, and blood sugar levels regulation. It acts as a cofactor for enzymes.Cobalt (Co)Cobalt is found in vitamin B12, an essential aspect of red blood cell formation and neurological function. There are also many cobalt-containing enzymes found in metabolic pathways of amino acids.Metals as TreatmentPlatinum (Pt)Platinum-based drugs, such as cisplatin, are commonly used in various cancer treatments. Cross-links form between the drugs and DNA, resulting in cell death. This is essential in getting rid of cancer cells that rapidly replicate.Cisplatin is a platinum containing drug used to treat cancerLithium (Li)Lithium can act as a mood stabilizer, as it can help regulate activity of neurotransmitters. This makes lithium salts useful in bipolar disorder treatments.Metal ToxicityAlthough metals are essential for many biological functions, in excess, metals can be harmful. Many diseases are a result of too much metal in the body. For example, hemochromatosis is a result of too much iron, resulting in tissue damage. Another disorder, Wilson’s disease, can be caused by too much copper building up in the body. Other exposure, to metals such as lead and mercury, can disturb biological processes and cause issues in both humans and other living things alike.Metal Deficiency and Associated DiseasesNot having enough of certain metals can also result in health problems. Low iron levels can cause anemia, which is caused by insufficient oxygen transport in the blood, leading to fatigue and weakness. Iron can be lost through sweat, so athletes such as distance runners are at higher risk for iron deficiencies. Deficiencies in zinc can result in impaired immune function and cognitive dysfunction, as without sufficient amounts of it, DNA synthesis, cell division, and many other vital cycles cannot occur.Heavy Metal ToxicityHeavy metals, such as lead, mercury, and cadmium, can be especially harmful. These metals can interfere with enzyme function, generate oxidative stress, and damage cellular structures as a result of their ability to bind with and disrupt essential biological molecules. An example of this is lead substituting for calcium in bone. This leads to the impairment of bone development, subsequently having an effect on its function. Another heavy metal, mercury, can bind to sulfur-containing enzymes. This inhibits their activity and causes neurological damage.ConclusionMetals in biology play a variety of roles, contributing to growth, development, and survival of living organisms. They have unique properties that allow for functions in different biological processes, but in moderation. Too much of any metal in the body can lead to toxic results. With the understanding of metals in biology, developments such as therapeutic treatments have the potential to be furthered.
