Editing Phosphorus (section)

==Biological role==
===Cells===
Inorganic phosphorus in the form of the phosphate {{chem2|PO4(3-)}} is required for all known forms of [[life]].{{r|Ruttenberg2011}} Phosphorus plays a major role in the structural framework of [[DNA]] and [[RNA]]. Living cells use phosphate to transport cellular energy with [[adenosine triphosphate]] (ATP), necessary for every cellular process that uses energy. ATP is also important for [[phosphorylation]], a key regulatory event in cells. Every living cell is encased in a membrane that separates it from its surroundings. Cellular membranes are composed of a phospholipid matrix and proteins, typically in the form of a bilayer. [[Phospholipid]]s are derived from [[glycerol]] with two of the glycerol hydroxyl (OH) protons replaced by fatty acids as an [[ester]], and the third hydroxyl proton has been replaced with phosphate bonded to another alcohol.{{r|Nelson2000}}

===Bone and teeth enamel===
{{see also|Calcium metabolism}}
The main component of bone is [[hydroxyapatite]] as well as amorphous forms of calcium phosphate, possibly including carbonate. Hydroxyapatite is the main component of tooth enamel. [[Water fluoridation]] enhances the resistance of teeth to decay by the partial conversion of this mineral to the still harder material [[fluorapatite]]:{{r|Greenwood1997}}
:{{chem2|Ca5(PO4)3OH + F- -> Ca5(PO4)3F + OH-}}
An average adult human contains about {{convert|0.7|kg|lb}} of phosphorus, about 85–90% in bones and teeth in the form of [[apatite]], and the remainder in soft tissues and extracellular fluids. The phosphorus content increases from about 0.5% by mass in infancy to 0.65–1.1% by mass in adults. In comparison, average phosphorus concentration in the blood is about 0.4&nbsp;g/L; about 70% of that is organic and 30% inorganic phosphates.{{r|Bernhardt2008}}

===Nutrition===
The main food sources for phosphorus are the same as those containing [[protein]], although proteins themselves do not contain phosphorus. For example, milk, meat, and soya typically also have phosphorus. Generally, if a diet includes sufficient protein and calcium, the amount of phosphorus is sufficient.{{r|Medline}}

According to the [[U.S. Institute of Medicine]], the estimated average requirement for phosphorus for people ages 19 and up is 580&nbsp;mg/day. The RDA is 700&nbsp;mg/day. RDAs are higher than EARs so as to identify amounts that will cover people with higher-than-average requirements. RDA for pregnancy and lactation are also 700&nbsp;mg/day. For people ages 1–18 years, the RDA increases with age from 460 to 1250&nbsp;mg/day. As for safety, the IOM sets [[tolerable upper intake level]] for phosphorus at 4000&nbsp;mg/day. Collectively, these values are referred to as the [[Dietary Reference Intake]].{{r|IOM1997}} The [[European Food Safety Authority]] (EFSA) refers to the collective set of information as Dietary Reference Values, with Population Reference Intake (PRI) instead of RDA, and Average Requirement instead of EAR.{{r|EFSA2024}} AI and UL are defined the same as in the United States. For people ages 15 and older, including pregnancy and [[lactation]], the AI is set at 550&nbsp;mg/day. For children ages 4–10, the AI is 440&nbsp;mg/day, and for ages 11–17 it is 640&nbsp;mg/day. These AIs are lower than the U.S. RDAs. In both systems, teenagers need more than adults.{{r|EFSA2017}} The EFSA reviewed the same safety question and decided that there was not sufficient information to set a UL.{{r|EFSA2006}}

Phosphorus deficiency may be caused by [[malnutrition]], by failure to absorb phosphate, and by metabolic syndromes that draw phosphate from the blood (such as in [[refeeding syndrome]] after malnutrition{{r|Mehanna2008}}) or passing too much of it into the urine. All are characterised by [[hypophosphatemia]], which is a condition of low levels of soluble phosphate levels in the blood serum and inside the cells. Symptoms of hypophosphatemia include neurological dysfunction and disruption of muscle and blood cells due to lack of [[Adenosine triphosphate|ATP]]. Too much phosphate can lead to diarrhoea and calcification (hardening) of organs and soft tissue, and can interfere with the body's ability to use iron, calcium, magnesium, and zinc.{{r|Anderson1996}}