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Selenium, which is an essential element for animals and prokaryotes and is a beneficial element for many plants, is the least-common of all the elements essential to life. [3] [63] Selenium acts as the catalytic center of several antioxidant enzymes, such as glutathione peroxidase, [11] and plays a wide variety of other biological roles.
Zinc is an essential trace element for humans, [8] [9] [10] animals, [11] plants [12] and for microorganisms [13] and is necessary for prenatal and postnatal development. [14] It is the second most abundant trace metal in humans after iron and it is the only metal which appears in all enzyme classes.
Under the classical theory of concepts, how human minds represent a category X, gives rise to a set of individually necessary conditions that define X. Together, these individually necessary conditions are sufficient to be X. [10] This contrasts with the probabilistic theory of concepts which states that no defining feature is necessary or ...
Boron is essential to plants, [43] [44] [45] but not animals. [6] Non-essential elements can sometimes appear in the body when they are chemically similar to essential elements (e.g. Rb + and Cs + replacing Na +), so that essentiality is not the same thing as uptake by a biological system. [1]
Chloride is necessary for osmosis and ionic balance; it also plays a role in photosynthesis. Copper, iron, manganese, molybdenum, and zinc are cofactors essential for the functioning of many enzymes. [19] For plants, deficiency in these elements often results in inefficient production of chlorophyll, manifested in chlorosis.
CHNOPS and CHON are mnemonic acronyms for the most common elements in living organisms. "CHON" stands for c arbon , h ydrogen , o xygen , and n itrogen , which together make up more than 95 percent of the mass of biological systems. [ 1 ] "
A chemical element, often simply called an element, is a type of atom which has a specific number of protons in its atomic nucleus (i.e., a specific atomic number, or Z). [ 1 ] The definitive visualisation of all 118 elements is the periodic table of the elements , whose history along the principles of the periodic law was one of the founding ...
A trace element is a chemical element of a minute quantity, a trace amount, especially used in referring to a micronutrient, [1] [2] 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 ...