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CalciumAn overview

ContentsArticlesOverview 1

Calcium 1

Isotopes 13

Isotopes of calcium 13

Miscellany 17

Calcium in biology 17Calcium metabolism 22Calcium deficiency 26

ReferencesArticle Sources and Contributors 28Image Sources, Licenses and Contributors 29

Article LicensesLicense 30

1

Overview

Calcium

Calcium

20Ca

potassium ← calcium → scandiumMg↑Ca↓Sr

Calcium in the periodic table

Appearance

dull gray, silver

Spectral lines of calcium

General properties

Name, symbol, number calcium, Ca, 20

Pronunciation /ˈkælsiəm/ KAL-see-əm

Element category alkaline earth metal

Group, period, block 2 (alkaline earth metals), 4, s

Standard atomic weight 40.078(4)

Electron configuration [Ar] 4s2

2, 8, 8, 2

History

Discovery Humphry Davy (1808)

Calcium 2

First isolation Humphry Davy (1808)

Physical properties

Phase solid

Density (near r.t.) 1.55 g·cm−3

Liquid density at m.p. 1.378 g·cm−3

Melting point 1115 K, 842 °C, 1548 °F

Boiling point 1757 K, 1484 °C, 2703 °F

Heat of fusion 8.54 kJ·mol−1

Heat of vaporization 154.7 kJ·mol−1

Molar heat capacity 25.929 J·mol−1·K−1

Vapor pressure

P (Pa) 1 10 100 1 k 10 k 100 k

at T (K) 864 956 1071 1227 1443 1755

Atomic properties

Oxidation states +2, +1(strongly basic oxide)

Electronegativity 1.00 (Pauling scale)

Ionization energies(more)

1st: 589.8 kJ·mol−1

2nd: 1145.4 kJ·mol−1

3rd: 4912.4 kJ·mol−1

Atomic radius 197 pm

Covalent radius 176±10 pm

Van der Waals radius 231 pm

Miscellanea

Crystal structure face-centered cubic

Magnetic ordering diamagnetic

Electrical resistivity (20 °C) 33.6 nΩ·m

Thermal conductivity 201 W·m−1·K−1

Thermal expansion (25 °C) 22.3 µm·m−1·K−1

Speed of sound (thin rod) (20 °C) 3810 m·s−1

Young's modulus 20 GPa

Shear modulus 7.4 GPa

Bulk modulus 17 GPa

Poisson ratio 0.31

Calcium 3

Mohs hardness 1.75

Brinell hardness 167 MPa

CAS registry number 7440-70-2

Most stable isotopes

Main article: Isotopes of calcium

iso NA half-life DM DE (MeV) DP

40Ca 96.941% >5.9×1021 y (β+β+) 0.194 40Ar

41Ca trace 1.03×105 y ε - 41K

42Ca 0.647% 42Ca is stable with 22 neutrons

43Ca 0.135% 43Ca is stable with 23 neutrons

44Ca 2.086% 44Ca is stable with 24 neutrons

45Ca syn 162.7 d β− 0.258 45Sc

46Ca 0.004% >2.8×1015 y (β−β−) 0.988 46Ti

47Ca syn 4.536 d β− 0.694, 1.99 47Sc

γ 1.297 -

48Ca 0.187% 4.3×1019 y β−β− 4.274 48Ti

(β−) 0.0058 48Sc

Decay modes in parentheses are predicted, but have not yet been observed

•• v•• t• e [1]

Calcium is the chemical element with symbol Ca and atomic number 20. Calcium is a soft gray alkaline earth metal,and is the fifth-most-abundant element by mass in the Earth's crust. Calcium is also the fifth-most-abundantdissolved ion in seawater by both molarity and mass, after sodium, chloride, magnesium, and sulfate.Calcium is essential for living organisms, in particular in cell physiology, where movement of the calcium ion Ca2+

into and out of the cytoplasm functions as a signal for many cellular processes. As a major material used inmineralization of bone, teeth and shells, calcium is the most abundant metal by mass in many animals.

Calcium 4

Notable characteristics

Flame test. Brick-red colororiginates from calcium.

In chemical terms, calcium is reactive and soft for a metal (though harder thanlead, it can be cut with a knife with difficulty). It is a silvery metallic element thatmust be extracted by electrolysis from a fused salt like calcium chloride. Onceproduced, it rapidly forms a gray-white oxide and nitride coating when exposed toair. In bulk form (typically as chips or "turnings"), the metal is somewhat difficultto ignite, more so even than magnesium chips; but, when lit, the metal burns in airwith a brilliant high-intensity orange-red light. Calcium metal reacts with water,generating hydrogen gas at a rate rapid enough to be noticeable, but not fastenough at room temperature to generate much heat, making it useful forgenerating hydrogen.[2] In powdered form, however, the reaction with water isextremely rapid, as the increased surface area of the powder accelerates thereaction with the water. Part of the slowness of the calcium–water reaction resultsfrom the metal being partly protected by insoluble white calcium hydroxide. Inwater solutions of acids, where this salt is soluble, calcium reacts vigorously.

Calcium, with a density of 1.55 g/cm3, is the lightest of the alkaline earth metals;magnesium (specific gravity 1.74) and beryllium (1.84) are more dense, althoughlighter in atomic mass. From strontium onward, the alkali earth metals becomemore dense with increasing atomic mass.

It has two allotropes.Calcium has a higher electrical resistivity than copper or aluminium, yetweight-for-weight, due to its much lower density, it is a rather better conductorthan either. However, its use in terrestrial applications is usually limited by itshigh reactivity with air.

Calcium salts are colorless from any contribution of the calcium, and ionicsolutions of calcium (Ca2+) are colorless as well. As with magnesium salts and other alkaline earth metal salts,calcium salts are often quite soluble in water. Notable exceptions include the hydroxide, the sulfate (unusual forsulfate salts), the carbonate and the phosphates. With the exception of the sulfate, even the insoluble ones listed arein general more soluble than its transition metal counterparts. When in solution, the calcium ion to the human tastevaries remarkably, being reported as mildly salty, sour, "mineral like" or even "soothing." It is apparent that manyanimals can taste, or develop a taste, for calcium, and use this sense to detect the mineral in salt licks or othersources. In human nutrition, soluble calcium salts may be added to tart juices without much effect to the averagepalate.

Calcium is the fifth-most-abundant element by mass in the human body, where it is a common cellular ionicmessenger with many functions, and serves also as a structural element in bone. It is the relativelyhigh-atomic-number calcium in the skeleton that causes bone to be radio-opaque. Of the human body's solidcomponents after drying and burning of organics (as for example, after cremation), about a third of the total"mineral" mass remaining, is the approximately one kilogram of calcium that composes the average skeleton (theremainder being mostly phosphorus and oxygen).

Calcium 5

H and K linesVisible spectra of many stars, including the Sun, exhibit strong absorption lines of singly ionized calcium. Prominentamong these are the H-line at 3968.5 Å and the K line at 3933.7 Å of singly ionized calcium, or Ca II. For the Sunand stars with low temperatures, the prominence of the H and K lines can be an indication of strong magneticactivity in the chromosphere. Measurement of periodic variations of these active regions can also be used to deducethe rotation periods of these stars.

CompoundsCalcium, combined with phosphate to form hydroxylapatite, is the mineral portion of human and animal bones andteeth. The mineral portion of some corals can also be transformed into hydroxylapatite.Calcium hydroxide (slaked lime) is used in many chemical refinery processes and is made by heating limestone athigh temperature (above 825 °C) and then carefully adding water to it. When lime is mixed with sand, it hardens intoa mortar and is turned into plaster by carbon dioxide uptake. Mixed with other compounds, lime forms an importantpart of Portland cement.Calcium carbonate (CaCO3) is one of the common compounds of calcium. It is heated to form quicklime (CaO),which is then added to water (H2O). This forms another material known as slaked lime (Ca(OH)2), which is aninexpensive base material used throughout the chemical industry. Chalk, marble, and limestone are all forms ofcalcium carbonate.When water percolates through limestone or other soluble carbonate rocks, it partially dissolves the rock and causescave formation and characteristic stalactites and stalagmites and also forms hard water. Other important calciumcompounds are calcium nitrate, calcium sulfide, calcium chloride, calcium carbide, calcium cyanamide and calciumhypochlorite.A few calcium compounds where calcium is in the oxidation state +1 have also been investigated recently.

IsotopesCalcium has five stable isotopes (40Ca, 42Ca, 43Ca, 44Ca and 46Ca), plus one more isotope (48Ca) that has such along half-live that for all practical purposes it can also be considered stable. The 20% range in relative mass amongnaturally occurring calcium isotopes is greater than for any other element except hydrogen and helium. Calcium alsohas a cosmogenic isotope, radioactive 41Ca, which has a half-life of 103,000 years. Unlike cosmogenic isotopes thatare produced in the atmosphere, 41Ca is produced by neutron activation of 40Ca. Most of its production is in theupper metre or so of the soil column, where the cosmogenic neutron flux is still sufficiently strong. 41Ca has receivedmuch attention in stellar studies because it decays to 41K, a critical indicator of solar-system anomalies.Ninety-seven percent of naturally occurring calcium is in the form of 40Ca. 40Ca is one of the daughter products of40K decay, along with 40Ar. While K-Ar dating has been used extensively in the geological sciences, the prevalenceof 40Ca in nature has impeded its use in dating. Techniques using mass spectrometry and a double spike isotopedilution have been used for K-Ca age dating.The most abundant isotope, 40Ca, has a nucleus of 20 protons and 20 neutrons. This is the heaviest stable isotope ofany element that has equal numbers of protons and neutrons. In supernova explosions, calcium is formed from thereaction of carbon with various numbers of alpha particles (helium nuclei), until the most common calcium isotope(containing 10 helium nuclei) has been synthesized.[citation needed]

Calcium 6

Isotope fractionationAs with the isotopes of other elements, a variety of processes fractionate, or alter the relative abundance of, calciumisotopes. The best studied of these processes is the mass-dependent fractionation[3] of calcium isotopes thataccompanies the precipitation of calcium minerals, such as calcite, aragonite and apatite, from solution. Isotopicallylight calcium is preferentially incorporated into minerals, leaving the solution from which the mineral precipitatedenriched in isotopically heavy calcium. At room temperature the magnitude of this fractionation is roughly 0.25‰(0.025%) per atomic mass unit (AMU). Mass-dependent differences in calcium isotope composition conventionallyare expressed the ratio of two isotopes (usually 44Ca/40Ca) in a sample compared to the same ratio in a standardreference material. 44Ca/40Ca varies by about 1% among common earth materials.Calcium isotope fractionation during mineral formation has led to several applications of calcium isotopes. Inparticular, the 1997 observation by Skulan and DePaolo that calcium minerals are isotopically lighter than thesolutions from which the minerals precipitate is the basis of analogous applications in medicine and inpaleooceanography. In animals with skeletons mineralized with calcium the calcium isotopic composition of softtissues reflects the relative rate of formation and dissolution of skeletal mineral. In humans changes in the calciumisotopic composition of urine have been shown to be related to changes in bone mineral balance. When the rate ofbone formation exceeds the rate of bone resorption, soft tissue 44Ca/40Ca rises. Soft tissue 44Ca/40Ca falls when boneresorption exceeds bone formation. Because of this relationship, calcium isotopic measurements of urine or bloodmay be useful in the early detection of metabolic bone diseases like osteoporosis.A similar system exists in the ocean, where seawater 44Ca/40Ca tends to rise when the rate of removal of Ca2+ fromseawater by mineral precipitation exceeds the input of new calcium into the ocean, and fall when calcium inputexceeds mineral precipitation. It follows that rising 44Ca/40Ca corresponds to falling seawater Ca2+ concentration,and falling 44Ca/40Ca corresponds to rising seawater Ca2+ concentration. In 1997 Skulan and DePaolo presented thefirst evidence of change in seawater 44Ca/40Ca over geologic time, along with a theoretical explanation of thesechanges. More recent papers have confirmed this observation, demonstrating that seawater Ca2+ concentration is notconstant, and that the ocean probably never is in “steady state” with respect to its calcium input and output. This hasimportant climatological implications, as the marine calcium cycle is closely tied to the carbon cycle (see below).

Geochemical cyclingCalcium provides an important link between tectonics, climate and the carbon cycle. In the simplest terms, uplift ofmountains exposes Ca-bearing rocks to chemical weathering and releases Ca2+ into surface water. This Ca2+

eventually is transported to the ocean where it reacts with dissolved CO2 to form limestone. Some of this limestonesettles to the sea floor where it is incorporated into new rocks. Dissolved CO2, along with carbonate and bicarbonateions, are referred to as dissolved inorganic carbon (DIC).

Travertine terraces Pamukkale, Turkey

The actual reaction is more complicated and involves the bicarbonateion (HCO3

−) that forms when CO2 reacts with water at seawater pH:

Ca2+

+ 2HCO−

3 → CaCO3 (limestone) + CO2 + H2O

Note that at ocean pH most of the CO2 produced in this reaction isimmediately converted back into HCO−

3. The reaction results in a net transport of one molecule of CO2 from the ocean/atmosphere into the lithosphere.

Calcium 7

The result is that each Ca2+ ion released by chemical weathering ultimately removes one CO2 molecule from thesurficial system (atmosphere, ocean, soils and living organisms), storing it in carbonate rocks where it is likely tostay for hundreds of millions of years. The weathering of calcium from rocks thus scrubs CO2 from the ocean andatmosphere, exerting a strong long-term effect on climate. Analogous cycles involving magnesium, and to a muchsmaller extent strontium and barium, have the same effect.As the weathering of limestone (CaCO3) liberates equimolar amounts of Ca2+ and CO2, it has no net effect on theCO2 content of the atmosphere and ocean. The weathering of silicate rocks like granite, on the other hand, is a netCO2 sink because it produces abundant Ca2+ but very little CO2.

HistoryLime as building material was used since prehistoric times going as far back as 7000 to 14000 BC. The first datedlime kiln dates back to 2500 BC and was found in Khafajah mesopotamia. Calcium (from Latin calx, genitive calcis,meaning "lime") was known as early as the first century when the Ancient Romans prepared lime as calcium oxide.Literature dating back to 975 AD notes that plaster of paris (calcium sulfate), is useful for setting broken bones. Itwas not isolated until 1808 in England when Sir Humphry Davy electrolyzed a mixture of lime and mercuric oxide.Davy was trying to isolate calcium; when he heard that Swedish chemist Jöns Jakob Berzelius and Pontin preparedcalcium amalgam by electrolyzing lime in mercury, he tried it himself. He worked with electrolysis throughout hislife and also discovered/isolated sodium, potassium, magnesium, boron and barium. Calcium metal was not availablein large scale until the beginning of the 20th century.

OccurrenceCalcium is not naturally found in its elemental state. Calcium occurs most commonly in sedimentary rocks in theminerals calcite, dolomite and gypsum. It also occurs in igneous and metamorphic rocks chiefly in the silicateminerals: plagioclases, amphiboles, pyroxenes and garnets.

ApplicationsCalcium is used• as a reducing agent in the extraction of other metals, such as uranium, zirconium, and thorium.• as a deoxidizer, desulfurizer, or decarbonizer for various ferrous and nonferrous alloys.• as an alloying agent used in the production of aluminium, beryllium, copper, lead, and magnesium alloys.• in the making of cements and mortars to be used in construction.• in the making of cheese, where calcium ions influence the activity of rennin in bringing about the coagulation of

milk.

Calcium compounds• Calcium carbonate (CaCO3) is used in manufacturing cement and mortar, lime, limestone (usually used in the

steel industry) and aids in production in the glass industry. It also has chemical and optical uses as mineralspecimens in toothpastes, for example.

• Calcium hydroxide solution (Ca(OH)2) (also known as limewater) is used to detect the presence of carbon dioxideby being bubbled through a solution. It turns cloudy where CO2 is present.

• Calcium arsenate (Ca3(AsO4)2) is used in insecticides.• Calcium carbide (CaC2) is used to make acetylene gas (for use in acetylene torches for welding) and in the

manufacturing of plastics.• Calcium chloride (CaCl2) is used in ice removal and dust control on dirt roads, in conditioner for concrete, as an

additive in canned tomatoes, and to provide body for automobile tires.

Calcium 8

• Calcium cyclamate (Ca(C6H11NHSO3)2) is used as a sweetening agent in several countries. In the United States itis no longer permitted for use because of suspected cancer-causing properties.

• Calcium gluconate (Ca(C6H11O7)2) is used as a food additive and in vitamin pills.• Calcium hypochlorite (Ca(OCl)2) is used as a swimming pool disinfectant, as a bleaching agent, as an ingredient

in deodorant, and in algaecide and fungicide.• Calcium permanganate (Ca(MnO4)2) is used in liquid rocket propellant, textile production, as a water sterilizing

agent and in dental procedures.• Calcium phosphate (Ca3(PO4)2) is used as a supplement for animal feed, fertilizer, in commercial production for

dough and yeast products, in the manufacture of glass, and in dental products.• Calcium phosphide (Ca3P2) is used in fireworks, rodenticide, torpedoes and flares.• Calcium stearate (Ca(C18H35O2)2) is used in the manufacture of wax crayons, cements, certain kinds of plastics

and cosmetics, as a food additive, in the production of water resistant materials and in the production of paints.• Calcium sulfate (CaSO4·2H2O) is used as common blackboard chalk, as well as, in its hemihydrate form better

known as Plaster of Paris.• Calcium tungstate (CaWO4) is used in luminous paints, fluorescent lights and in X-ray studies.• Hydroxylapatite (Ca5(PO4)3(OH), but is usually written Ca10(PO4)6(OH)2) makes up seventy percent of bone.

Also carbonated-calcium deficient hydroxylapatite is the main mineral of which dental enamel and dentin arecomprised.

Nutrition

Recommended adequate intake by the IOM for calcium:

Age Calcium (mg/day)

0–6 months 200

7–12 months 260

1–3 years 700

4–8 years 1000

9–18 years 1300

19–50 years 1000

51–70 years (male) 1000

51–70 years (female) 1200

71+ years 1200

Calcium is an important component of a healthy diet and a mineral necessary for life. The National Osteoporosis Foundation says, "Calcium plays an important role in building stronger, denser bones early in life and keeping bones strong and healthy later in life." Approximately 99 percent of the body's calcium is stored in the bones and teeth. The rest of the calcium in the body has other important uses, such as some exocytosis, especially neurotransmitter release, and muscle contraction. In the electrical conduction system of the heart, calcium replaces sodium as the mineral that depolarizes the cell, proliferating the action potential. In cardiac muscle, sodium influx commences an action potential, but during potassium efflux, the cardiac myocyte experiences calcium influx, prolonging the action potential and creating a plateau phase of dynamic equilibrium. Long-term calcium deficiency can lead to rickets and poor blood clotting and in case of a menopausal woman, it can lead to osteoporosis, in which the bone deteriorates and there is an increased risk of fractures. While a lifelong deficit can affect bone and tooth formation, over-retention can cause hypercalcemia (elevated levels of calcium in the blood), impaired kidney function and decreased absorption of other minerals. Several sources suggest a correlation between high calcium intake (2000 mg per day, or

Calcium 9

twice the U.S. recommended daily allowance, equivalent to six or more glasses of milk per day) and prostate cancer.High calcium intakes or high calcium absorption were previously thought to contribute to the development of kidneystones. However, a high calcium intake has been associated with a lower risk for kidney stones in more recentresearch. Vitamin D is needed to absorb calcium.Dairy products, such as milk and cheese, are a well-known source of calcium. Some individuals are allergic to dairyproducts and even more people, in particular those of non Indo-European descent, are lactose-intolerant, leavingthem unable to consume non-fermented dairy products in quantities larger than about half a liter per serving. Others,such as vegans, avoid dairy products for ethical and health reasons.Many good vegetable sources of calcium exist, including seaweeds such as kelp, wakame and hijiki; nuts and seedslike almonds, hazelnuts, sesame, and pistachio; blackstrap molasses; beans (especially soy beans); figs; quinoa; okra;rutabaga; broccoli; dandelion leaves; and kale. In addition, for some drinks (like soy milk or orange juice[citation

needed]) it is typical to be fortified with calcium.Numerous vegetables, notably spinach, chard and rhubarb have a high calcium content, but they may also containvarying amounts of oxalic acid that binds calcium and reduces its absorption. The same problem may to a degreeaffect the absorption of calcium from amaranth, collard greens, and chicory greens. This process may also be relatedto the generation of calcium oxalate.An overlooked source of calcium is eggshell, which can be ground into a powder and mixed into food or a glass ofwater.The calcium content of most foods can be found in the USDA National Nutrient Database.

Dietary supplements

500 milligram calcium supplements made fromcalcium carbonate

Calcium supplements are used to prevent and to treat calciumdeficiencies. Office of Dietary Supplements (National Institutes ofHealth) recommends that no more than 600 mg of supplement shouldbe taken at a time because the percent of calcium absorbed decreases asthe amount of calcium in the supplement increases. It is thereforerecommended to spread doses throughout the day.[4] Recommendeddaily calcium intake for adults ranges from 1000 to 1300 mg. Calciumsupplements may have side effects such as bloating and constipation insome people. It is suggested that taking the supplements with food mayaid in nullifying these side effects.

Vitamin D is added to some calcium supplements. Proper vitamin D status is important because vitamin D isconverted to a hormone in the body, which then induces the synthesis of intestinal proteins responsible for calciumabsorption.

•• The absorption of calcium from most food and commonly used dietary supplements is very similar. This iscontrary to what many calcium supplement manufacturers claim in their promotional materials.

• Milk is an excellent source of dietary calcium for those whose bodies tolerate it because it has a highconcentration of calcium and the calcium in milk is excellently absorbed.

• Soymilk and other vegetable milks are usually sold with calcium added so that their calcium concentration is ashigh as in milk.

• Also different kind of juices boosted with calcium are widely available.• Calcium carbonate is the most common and least expensive calcium supplement. It should be taken with food,

and depends on low pH levels (acidic) for proper absorption in the intestine. Some studies suggests that the absorption of calcium from calcium carbonate is similar to the absorption of calcium from milk. While most people digest calcium carbonate very well, some might develop gastrointestinal discomfort or gas. Taking

Calcium 10

magnesium with it can help to avoid constipation. Calcium carbonate is 40% elemental calcium. 1000 mg willprovide 400 mg of calcium. However, supplement labels will usually indicate how much calcium is present ineach serving, not how much calcium carbonate is present.

• Antacids frequently contain calcium carbonate, and are a commonly used, inexpensive calcium supplement.• Coral calcium is a salt of calcium derived from fossilized coral reefs. Coral calcium is composed of calcium

carbonate and trace minerals.• Calcium citrate can be taken without food and is the supplement of choice for individuals with achlorhydria or

who are taking histamine-2 blockers or proton-pump inhibitors. Calcium citrate is about 21% elemental calcium.1000 mg will provide 210 mg of calcium. It is more expensive than calcium carbonate and more of it must betaken to get the same amount of calcium.

• Calcium phosphate costs more than calcium carbonate, but less than calcium citrate. MicrocrystallineHydroxyapatite (MH) is one of several forms of calcium phosphate used as a dietary supplement. Hydroxyapatiteis about 40% calcium.

• Calcium lactate has similar absorption as calcium carbonate, but is more expensive. Calcium lactate and calciumgluconate are less concentrated forms of calcium and are not practical oral supplements.

• Calcium chelates are synthetic calcium compounds in which calcium is bound to an organic molecule, such asmalate, aspartate, or fumarate. These forms of calcium may be better absorbed on an empty stomach. However, ingeneral they are absorbed similarly to calcium carbonate and other common calcium supplements when takenwith food. The "chelate" mimics the action that natural food performs by keeping the calcium soluble in theintestine. Thus, on an empty stomach, in some individuals, chelates might, in theory, be absorbed better.

Cardiovascular ImpactA study investigating the effects of personal calcium supplement use on cardiovascular risk in the Women’s HealthInitiative Calcium/Vitamin D Supplementation Study (WHI CaD Study) found a modestly increased risk ofcardiovascular events, particularly myocardial infarction in postmenopausal women. A broad recommendation ofcalcium/vitamin D supplements is therefore not warranted.[5] In contrast, the authors of a 2013 literature reviewconcluded that the benefits of calcium supplementation, such as on bone health, appear to outweigh any risk calciumsupplementation may theoretically pose to the cardiovascular health.

OsteoporosisSuch studies often do not test calcium alone, but rather combinations of calcium and vitamin D. Randomizedcontrolled trials found both positive and negative effects. The different results may be explained by doses of calciumand underlying rates of calcium supplementation in the control groups.

CancerA meta-analysis by the international Cochrane Collaboration of two randomized controlled trials found that calcium"might contribute to a moderate degree to the prevention of adenomatous colonic polyps".More recent studies were conflicting, and one that was positive for effect (Lappe, et al.) did control for a possibleanti-carcinogenic effect of vitamin D, which was found to be an independent positive influence from calcium-aloneon cancer risk (see second study below).• A randomized controlled trial found that 1000 mg of elemental calcium and 400 IU of vitamin D3 had no effect on

colorectal cancer.• A randomized controlled trial found that 1400–1500 mg supplemental calcium and 1100 IU vitamin D3 reduced

aggregated cancers with a relative risk of 0.402.• An observational cohort study found that high calcium and vitamin D intake was associated with "lower risk of

developing premenopausal breast cancer."

Calcium 11

Hazards and toxicityCompared with other metals, the calcium ion and most calcium compounds have low toxicity. This is not surprisinggiven the very high natural abundance of calcium compounds in the environment and in organisms. Calcium posesfew serious environmental problems, with kidney stones the most common side-effect in clinical studies. Acutecalcium poisoning is rare, and difficult to achieve unless calcium compounds are administered intravenously. Forexample, the oral median lethal dose (LD50) for rats for calcium carbonate and calcium chloride are 6.45 and1.4 g/kg, respectively.Calcium metal is hazardous because of its sometimes-violent reactions with water and acids. Calcium metal is foundin some drain cleaners, where it functions to generate heat and calcium hydroxide that saponifies the fats andliquefies the proteins (e.g., hair) that block drains. When swallowed calcium metal has the same effect on the mouth,esophagus and stomach, and can be fatal.[6]

Excessive consumption of calcium carbonate antacids/dietary supplements (such as Tums) over a period of weeks ormonths can cause milk-alkali syndrome, with symptoms ranging from hypercalcemia to potentially fatal renalfailure. What constitutes “excessive” consumption is not well known and, it is presumed, varies a great deal fromperson to person. Persons consuming more than 10 grams/day of CaCO3 (=4 g Ca) are at risk of developingmilk-alkali syndrome, but the condition has been reported in at least one person consuming only 2.5 grams/day ofCaCO3 (=1 g Ca), an amount usually considered moderate and safe.Oral calcium supplements diminish the absorption of thyroxine when taken within four to six hours of each other.Thus, people taking both calcium and thyroxine run the risk of inadequate thyroid hormone replacement and thencehypothyroidism if they take them simultaneously or near-simultaneously.Wikipedia:Identifying reliable sources(medicine)ExcessiveWikipedia:Vagueness calcium supplementation can be detrimental to cardiovascular health, especially inmen.

References[1] http:/ / en. wikipedia. org/ w/ index. php?title=Template:Infobox_calcium& action=edit[2] Theodore Gray. The Elements. Page 55[3] http:/ / toolserver. org/ %7Edispenser/ cgi-bin/ dab_solver. py?page=Calcium& editintro=Template:Disambiguation_needed/ editintro&

client=Template:Dn[4] "Dietary Supplement Fact Sheet: Calcium – Quick Facts (http:/ / ods. od. nih. gov/ factsheets/ Calcium-QuickFacts/ ) — Retrieved 28 August

2013[5] M. J. Bolland, A. Grey, A. Avenell, G. D. Gamble, I. R. Reid. (2011). "Calcium supplements with or without vitamin D and risk of

cardiovascular events: reanalysis of the Women's Health Initiative limited access dataset and meta-analysis." BMJ;342:d2040 DOI:10.1136/bmj.d2040 (http:/ / www. bmj. com/ content/ 342/ bmj. d2040)

[6][6] Rumack BH. POISINDEX. Information System Micromedex, Inc., Englewood, CO, 2010; CCIS Volume 143. Hall AH and Rumack BH(Eds)

Calcium 12

Further reading• Rebecca J. Donatelle. Health, The Basics. 6th ed. San Francisco: Pearson Education, Inc. 2005.

External links• WebElements.com – Calcium (http:/ / www. webelements. com/ webelements/ elements/ text/ Ca/ index. html)• Calcium (http:/ / www. periodicvideos. com/ videos/ 020. htm) at The Periodic Table of Videos (University of

Nottingham)• USDA National Nutrient Database, Calcium content of selected foods (http:/ / www. nal. usda. gov/ fnic/

foodcomp/ Data/ SR17/ wtrank/ sr17a301. pdf)• UK Food Standards Agency: Calcium (http:/ / www. eatwell. gov. uk/ healthydiet/ nutritionessentials/

vitaminsandminerals/ calcium/ )• Nutrition fact sheet from the National Institutes of Health (http:/ / ods. od. nih. gov/ factsheets/ calcium. asp)

13

Isotopes

Isotopes of calciumCalcium (Ca) has a total of 24 isotopes, from 34Ca to 57Ca. There are five observationally stable isotopes (40Ca,42Ca, 43Ca, 44Ca and 46Ca), plus one isotope (48Ca) with such a long half-life that for all practical purposes it can beconsidered stable. The most abundant isotope, 40Ca, as well as the rare 46Ca, are theoretically unstable on energeticgrounds, but their decay has not been observed. Calcium also has a cosmogenic isotope, radioactive 41Ca, which hasa half-life of 102,000 years. Unlike cosmogenic isotopes that are produced in the atmosphere, 41Ca is produced byneutron activation of 40Ca. Most of its production is in the upper metre or so of the soil column where thecosmogenic neutron flux is still sufficiently strong. 41Ca has received much attention in stellar studies because itdecays to 41K, a critical indicator of solar-system anomalies. The most stable artificial radioisotope is 45Ca, with ahalf-life of 163 days.All other isotopes have half-lives of 163 days or less, most under a minute. The least stable is 34Ca with a half-lifeshorter than 35 nanoseconds.40Ca comprises about 97% of naturally occurring calcium. 40Ca is also one of the daughter products of 40K decay,along with 40Ar. While K-Ar dating has been used extensively in the geological sciences, the prevalence of 40Ca innature has impeded its use in dating. Techniques using mass spectrometry and a double spike isotope dilution havebeen used for K-Ca age dating.Standard atomic mass: 40.078(4) u

Table

nuclidesymbol

Z(p) N(n) isotopic mass(u)

half-life[1] decaymode(s)[2][3]

daughterisotope(s)[4]

nuclearspin

representativeisotopic

composition(mole

fraction)

range ofnatural

variation(mole fraction)

34Ca 20 14 34.01412(32)# <35 ns p 33K 0+

35Ca 20 15 35.00494(21)# 25.7(2) ms β+ (>99.9%) 35K 1/2+#

β+, p (<.1%) 34Ar36Ca 20 16 35.99309(4) 102(2) ms β+, p

(56.8%)35Ar 0+

β+ (43.2%) 36K37Ca 20 17 36.985870(24) 181.1(10)

msβ+, p(74.5%)

36Ar (3/2+)

β+ (25.5%) 37K38Ca 20 18 37.976318(5) 440(8) ms β+ 38K 0+

39Ca 20 19 38.9707197(20) 859.6(14)ms

β+ 39K 3/2+

Isotopes of calcium 14

40Ca[5] 20 20 39.96259098(22) Observationally Stable[6] 0+ 0.96941(156) 0.96933-0.96947

41Ca 20 21 40.96227806(26) 1.02(7)×105

aEC 41K 7/2- Trace[7]

42Ca 20 22 41.95861801(27) Stable 0+ 0.00647(23) 0.00646-0.00648

43Ca 20 23 42.9587666(3) Stable 7/2- 0.00135(10) 0.00135-0.00135

44Ca 20 24 43.9554818(4) Stable 0+ 0.02086(110) 0.02082-0.02092

45Ca 20 25 44.9561866(4) 162.67(25)d

β- 45Sc 7/2-

46Ca 20 26 45.9536926(24) Observationally Stable[8] 0+ 4(3)×10−5 4×10−5-4×10−5

47Ca 20 27 46.9545460(24) 4.536(3) d β- 47Sc 7/2-

48Ca[9] 20 28 47.952534(4) 43(38)×1018

aβ-β-[10] 48Ti 0+ 0.00187(21) 0.00186-0.00188

49Ca 20 29 48.955674(4) 8.718(6)min

β- 49Sc 3/2-

50Ca 20 30 49.957519(10) 13.9(6) s β- 50Sc 0+

51Ca 20 31 50.9615(1) 10.0(8) s β- (>99.9%) 51Sc (3/2-)#

β-, n (<.1%) 50Sc52Ca 20 32 51.96510(75) 4.6(3) s β- (98%) 52Sc 0+

β-, n (2%) 51Sc53Ca 20 33 52.97005(54)# 90(15) ms β- (70%) 53Sc 3/2-#

β-, n (30%) 52Sc54Ca 20 34 53.97435(75)# 50# ms

[>300 ns]β-, n 53Sc 0+

β- 54Sc55Ca 20 35 54.98055(75)# 30# ms

[>300 ns]β- 55Sc 5/2-#

56Ca 20 36 55.98557(97)# 10# ms[>300 ns]

β- 56Sc 0+

57Ca 20 37 56.99236(107)# 5# ms β- 57Sc 5/2-#

β-, n 56Sc

[1][1] Bold for isotopes with half-lives longer than the age of the universe (nearly stable)[2] http:/ / www. nucleonica. net/ unc. aspx[3] Abbreviations:

EC: Electron capture[4][4] Bold for stable isotopes[5][5] Heaviest nuclide with equal numbers of protons and neutrons with no observed decay[6] Believed to undergo β+β+ decay to 40Ar with a half-life no less than 5.9×1021 a[7][7] Cosmogenic nuclide[8] Believed to undergo β-β- decay to 46Ti with a half-life no less than 2.8×1015 a[9] Primordial radionuclide[10] Lightest nuclide known to undergo double beta decay

Isotopes of calcium 15

Notes•• Evaluated isotopic composition is for most but not all commercial samples.•• The precision of the isotope abundances and atomic mass is limited through variations. The given ranges should

be applicable to any normal terrestrial material.•• Geologically exceptional samples are known in which the isotopic composition lies outside the reported range.

The uncertainty in the atomic mass may exceed the stated value for such specimens.•• Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins

with weak assignment arguments are enclosed in parentheses.•• Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values

denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which useexpanded uncertainties.

• Nuclide masses are given by IUPAP Commission on Symbols, Units, Nomenclature, Atomic Masses andFundamental Constants (SUNAMCO).

• Isotope abundances are given by IUPAC Commission on Isotopic Abundances and Atomic Weights.

References•• Isotope masses from:

• G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (2003). "The NUBASE evaluation of nuclearand decay properties" (http:/ / www. nndc. bnl. gov/ amdc/ nubase/ Nubase2003. pdf). Nuclear Physics A 729:3–128. Bibcode: 2003NuPhA.729....3A (http:/ / adsabs. harvard. edu/ abs/ 2003NuPhA. 729. . . . 3A). doi:10.1016/j.nuclphysa.2003.11.001 (http:/ / dx. doi. org/ 10. 1016/ j. nuclphysa. 2003. 11. 001).

•• Isotopic compositions and standard atomic masses from:• J. R. de Laeter, J. K. Böhlke, P. De Bièvre, H. Hidaka, H. S. Peiser, K. J. R. Rosman and P. D. P. Taylor

(2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)" (http:/ / www. iupac. org/publications/ pac/ 75/ 6/ 0683/ pdf/ ). Pure and Applied Chemistry 75 (6): 683–800. doi:10.1351/pac200375060683 (http:/ / dx. doi. org/ 10. 1351/ pac200375060683).

• M. E. Wieser (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)" (http:/ / iupac. org/publications/ pac/ 78/ 11/ 2051/ pdf/ ). Pure and Applied Chemistry 78 (11): 2051–2066. doi:10.1351/pac200678112051 (http:/ / dx. doi. org/ 10. 1351/ pac200678112051). Lay summary (http:/ / old.iupac. org/ news/ archives/ 2005/ atomic-weights_revised05. html).

• Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.• G. Audi, A. H. Wapstra, C. Thibault, J. Blachot and O. Bersillon (2003). "The NUBASE evaluation of nuclear

and decay properties" (http:/ / www. nndc. bnl. gov/ amdc/ nubase/ Nubase2003. pdf). Nuclear Physics A 729:3–128. Bibcode: 2003NuPhA.729....3A (http:/ / adsabs. harvard. edu/ abs/ 2003NuPhA. 729. . . . 3A). doi:10.1016/j.nuclphysa.2003.11.001 (http:/ / dx. doi. org/ 10. 1016/ j. nuclphysa. 2003. 11. 001).

• National Nuclear Data Center. "NuDat 2.1 database" (http:/ / www. nndc. bnl. gov/ nudat2/ ). BrookhavenNational Laboratory. Retrieved September 2005.

• N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85thed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9.

Isotopes of calcium 16

Further reading• C.Michael Hogan. 2010. Calcium. ed. A.Jorgenson and C.Cleveland. Encyclopedia of Earth, National Council for

Science and the Environment, Washington DC (http:/ / www. eoearth. org/ article/ Calcium?topic=49557)

External links• Calcium isotopes data from The Berkeley Laboratory Isotopes Project's (http:/ / ie. lbl. gov/ education/ parent/

Ca_iso. htm)

Isotopes of potassium Isotopes of calcium Isotopes of scandium

Table of nuclides

17

Miscellany

Calcium in biologyCalcium (Ca2+) plays a pivotal role in the physiology and biochemistry of organisms and the cell. It plays animportant role in signal transduction pathways, where it acts as a second messenger, in neurotransmitter release fromneurons, contraction of all muscle cell types, and fertilization. Many enzymes require calcium ions as a cofactor,those of the blood-clotting cascade being notable examples. Extracellular calcium is also important for maintainingthe potential difference across excitable cell membranes, as well as proper bone formation.Calcium levels in mammals are tightly regulated,[] with bone acting as the major mineral storage site. Calcium ions,Ca2+, are released from bone into the bloodstream under controlled conditions. Calcium is transported through thebloodstream as dissolved ions or bound to proteins such as serum albumin. Parathyroid hormone secreted by theparathyroid gland regulates the resorption of Ca2+ from bone, reabsorption in the kidney back into circulation, andincreases in the activation of vitamin D3 to Calcitriol. Calcitriol, the active form of vitamin D3, promotes absorptionof calcium from the intestines and the mobilization of calcium ions from bone matrix. Calcitonin secreted from theparafollicular cells of the thyroid gland also affects calcium levels by opposing parathyroid hormone; however, itsphysiological significance in humans is dubious.Calcium storages are intracellular organelles, that constantly accumulate Ca2+ ions and release them during certaincellular events. Intracellular Ca2+ storages include mitochondria and the endoplasmic reticulum.

Eukaryota

Animalia

Vertebrates

In vertebrates, calcium ions, like many other ions, are of such vital importance to many physiological processes thatits concentration is maintained within specific limits to ensure adequate homeostasis. This is evidenced by humanplasma calcium, which is one of the most closely regulated physiological variables in the human body. Normalplasma levels vary between 1 and 2% over any given time. Approximately half of all ionized calcium circulates in itsunbound form, with the other half being complexed with plasma proteins such as albumin, as well as anionsincluding bicarbonate, citrate, phosphate, and sulfate.

Calcium in biology 18

Calcium regulation in the human body.

Different tissues contain calcium in differentconcentrations. For instance, Ca2+ (mostly calciumphosphate and some calcium sulfate) is the mostimportant (and specific) element of bone and calcifiedcartilage. In humans, the total body content of calciumis present mostly in the form of bone mineral (roughly99%). In this state, it is largely unavailable forexchange/bioavailability. The way to overcome this isthrough the process of bone resorption, in whichcalcium is liberated into the bloodstream through theaction of bone osteoclasts. The remainder of calcium ispresent within the extracellular and intracellular fluids.

Within a typical cell, the intracellular concentration ofionized calcium is roughly 100 nM, but is subject toincreases of 10– to 100-fold during various cellularfunctions. The intracellular calcium level is keptrelatively low with respect to the extracellular fluid, byan approximate magnitude of 12,000-fold. Thisgradient is maintained through various plasmamembrane calcium pumps that utilize ATP for energy, as well as a sizable storage within intracellular compartments.In electrically excitable cells, such as skeletal and cardiac muscles and neurons, membrane depolarization leads to aCa2+ transient with cytosolic Ca2+ concentration reaching 400 nM and above. Mitochondria are capable ofsequestering and storing some of that Ca2+. It has been estimated that mitochondrial matrix free calciumconcentration rises to the tens of micromolar levels in situ during neuronal activity.

Effects

The effects of calcium on human cells are specific, meaning that different types of cells respond in different ways.However, in certain circumstances, its action may be more general. Ca2+ ions are one of the most widespread secondmessengers used in signal transduction. They make their entrance into the cytoplasm either from outside the cellthrough the cell membrane via calcium channels (such as Calcium-binding proteins or voltage-gated calciumchannels), or from some internal calcium storages such as the endoplasmic reticulum and mitochondria. Levels ofintracellular calcium are regulated by transport proteins that remove it from the cell. For example, thesodium-calcium exchanger uses energy from the electrochemical gradient of sodium by coupling the influx ofsodium into cell (and down its concentration gradient) with the transport of calcium out of the cell. In addition, theplasma membrane Ca2+ ATPase (PMCA) obtains energy to pump calcium out of the cell by hydrolysing adenosinetriphosphate (ATP). In neurons, voltage-dependent, calcium-selective ion channels are important for synaptictransmission through the release of neurotransmitters into the synaptic cleft by vesicle fusion of synaptic vesicles.Calcium's function in muscle contraction was found as early as 1882 by Ringer. Subsequent investigations were toreveal its role as a messenger about a century later. Because its action is interconnected with cAMP, they are calledsynarchic messengers. Calcium can bind to several different calcium-modulated proteins such as troponin-C (the firstone to be identified) and calmodulin, proteins that are necessary for promoting contraction in muscle.

Calcium in biology 19

Cell type Effect

secretory cells (mostly) ↑secretion (vesicle fusion)

juxtaglomerular cell ↓secretion

Parathyroid chief cells ↓secretion

Neurons transmission (vesicle fusion)

T cells Activation in response to antigen presentation to the T cell receptor

myocytes •• contraction• Activation of protein kinase C

Various Activation of protein kinase CFurther reading: Function of protein kinase C

Reference ranges for blood tests, showing calcium levels in purple at right.

Negative effects and pathology

Substantial decreases in extracellular Ca2+ ion concentrations may result in a condition known as hypocalcemictetany, which is marked by spontaneous motor neuron discharge. In addition, severe hypocalcaemia will begin toaffect aspects of blood coagulation and signal transduction.Ca2+ ions can damage cells if they enter in excessive numbers (for example, in the case of excitotoxicity, orover-excitation of neural circuits, which can occur in neurodegenerative diseases, or after insults such as braintrauma or stroke). Excessive entry of calcium into a cell may damage it or even cause it to undergo apoptosis, ordeath by necrosis. Calcium also acts as one of the primary regulators of osmotic stress (Osmotic shock). Chronicallyelevated plasma calcium (hypercalcemia) is associated with cardiac arrhythmias and decreased neuromuscularexcitability. One cause of hypercalcemia is a condition known as hyperparathyroidism.

Invertebrates

Some invertebrates use calcium compounds for building their exoskeleton (shells and carapaces) or endoskeleton(echinoderm plates and poriferan calcareous spicules).

Plantae

Stomata closing

When ABA signals the guard cells, free Ca2+ ions enter the cytosol from both outside the cell and internal stores,reversing the concentration gradient so the K+ ions begin exiting the cell. The loss of solutes makes the cell flaccidand closes the stomatal pores.

Calcium in biology 20

Cellular division

Calcium is a necessary ion in the formation of the mitotic spindle. Without the mitotic spindle, cellular divisioncannot occur. Although young leaves have a higher need for calcium, older leaves contain higher amounts of calciumbecause calcium is relatively immobile through the plant. It is not transported through the phloem because it can bindwith other nutrient ions and precipitate out of liquid solutions.

Structural roles

Ca2+ ions are an essential component of plant cell walls and cell membranes, and are used as cations to balanceorganic anions in the plant vacuole. The Ca2+ concentration of the vacuole may reach millimolar levels. The moststriking use of Ca2+ ions as a structural element in plants occurs in the marine coccolithophores, which use Ca2+ toform the calcium carbonate plates, with which they are covered.Calcium is needed to form the pectin in the middle lamella of newly formed cells.Calcium is needed to stabilize the permeability of cell membranes. Without calcium, the cell walls are unable tostabilize and hold their contents. This is particularly important in developing fruits. Without calcium, the cell wallsare weak and unable to hold the contents of the fruit.Some plants accumulate Ca in their tissues, thus making them more firm. Calcium is stored as Ca-oxalate crystals inplastids.Calcium coordination plays an important role in defining the structure and function of proteins. An example aprotein with calcium coordination is von Willebrand factor (vWF) which has an essential role in blood clot formationprocess. It is discovered -using single molecule optical tweezers measurement - that calcium-bound vWF acts as ashear force sensor in the blood. Shear force leads to unfolding of the A2 domain of vWF whose refolding rate isdramatically enhanced in the presence of calcium.[1]

Cell signaling

Ca2+ ions are usually kept at nanomolar levels in the cytosol of plant cells, and act in a number of signal transductionpathways as second messengers.

ProtistsMany protists make use of calcium.

MeasurementThe amount of calcium in blood (more specifically, in blood plasma) can be measured as total calcium, whichincludes both protein-bound and free calcium. In contrast, ionized calcium is a measure of free calcium. Anabnormally high level of calcium in plasma is termed hypercalcemia and an abnormally low level is termedhypocalcemia, with "abnormal" generally referring to levels outside the reference range.

Calcium in biology 21

Reference ranges for blood tests for calcium

Target Lower limit Upper limit Unit

Ionized calcium 1.03, 1.10[2] 1.23, 1.30 mmol/L

4.1,[3] 4.4 4.9, 5.2 mg/dL

Total calcium 2.1,[4][3] 2.2 2.5, 2.6, 2.8 mmol/L

8.4, 8.5[5] 10.2, 10.5 mg/dL

The total amount of Ca2+ present in a tissue may be measured using Atomic absorption spectroscopy, in which thetissue is vaporized and combusted. To measure Ca2+ concentration or spatial distribution within the cell cytoplasm invivo, a range of fluorescent reporters may be used. These include cell permeable, calcium-binding fluorescent dyessuch as Fura-2 or genetically engineered variant of green fluorescent protein (GFP) named Cameleon.

Food sourcesThe USDA web site has a very complete table of calcium content (in mg) of common foods per common measures(link below).Calcium amount in foods, 100 g:• parmesan (cheese) = 1140 mg• milk powder = 909 mg• Cheddar cheese = 720 mg• tahini paste = 427 mg• molasses = 273 mg• hazelnuts = 114 mg• almonds = 234 mg• sesame seeds (unhulled) = 125 mg• nonfat cow milk = 122 mg• plain whole-milk yogurt = 121 mg• ricotta (skimmed milk cheese) = 90 mg• brown sugar = 85 mg• lentils = 79 mg• wheat germs = 72 mg• pigeon peas = 62.7 mg• eggs, boiled = 50 mg• chickpeas = 53.1• flour = 41 mg• orange = 40 mg• human milk = 33 mg• rice, white, long-grain, parboiled, enriched, cooked = 19 mg• trout = 19 mg• beef = 12 mg• cod = 11 mg• horse meat = 10 mg• honey = 5 mg•• white sugar = 0 mg

Calcium in biology 22

References[1] Jakobi AJ, Mashaghi A, Tans SJ, Huizinga EG. Calcium modulates force sensing by the von Willebrand factor A2 domain. Nature Commun.

2011 Jul 12;2:385. (http:/ / www. nature. com/ ncomms/ journal/ v2/ n7/ full/ ncomms1385. html)[2][2] Reference range list from Uppsala University Hospital ("Laborationslista"). Artnr 40284 Sj74a. Issued on April 22, 2008[3] Derived from molar values using molar mass of 40.08 g•mol−1[4][4] Last page of[5] Blood Test Results - Normal Ranges (http:/ / www. bloodbook. com/ ranges. html) Bloodbook.Com

External links• USDA national nutritional database, Calcium content of selected foods (http:/ / www. nal. usda. gov/ fnic/

foodcomp/ Data/ SR17/ wtrank/ sr17a301. pdf)• Calcium and vitamin D (http:/ / www. nof. org/ prevention/ calcium_and_VitaminD. htm).

Calcium metabolism

Calcium

Calcium metabolism or calciumhomeostasis is the mechanism bywhich the body maintains adequatecalcium levels. Derangements of thismechanism lead to hypercalcemia orhypocalcemia, both of which can haveimportant consequences for health.

Calcium location and quantityCalcium is the most abundant mineral in the human body. The average adult body contains in total approximately1 kg, 99% in the skeleton in the form of calcium phosphate salts. The extracellular fluid (ECF) containsapproximately 22.5 mmol, of which about 9 mmol is in the plasma. Approximately 500 mmol of calcium isexchanged between bone and the ECF over a period of twenty-four hours.

Biological functions•• Structural function: Supporting material in bones. Present as calcium phosphate.•• Signalling function: Intracellular calcium functions as a second messenger for the secretion of some hormones

and neurotransmitters. Also acts as an intracellular permeation regulator and mediator of muscle contraction.•• Enzymatic function: Calcium acts as a coenzyme for clotting factors.Calcium also causes the release of Acetylcholine from pre-synaptic terminals in the transmission of nerve impulses.Calcium causes the contraction of muscles, removing the Triosephosphate isomerase (TPI) subunit from Myosinhead which has ATPase activity to cause contraction.

Calcium metabolism 23

Normal rangesThe plasma level of calcium is closely regulated with a normal total calcium of 2.2-2.6 mmol/L (9-10.5 mg/dL) anda normal ionized calcium of 1.1-1.4 mmol/L (4.5-5.6 mg/dL). The amount of total calcium varies with the level ofserum albumin, a protein to which calcium is bound. The biologic effect of calcium is determined by the amount ofionized calcium, rather than the total calcium. Ionized calcium does not vary with the albumin level, and therefore itis useful to measure the ionized calcium level when the serum albumin is not within normal ranges, or when acalcium disorder is suspected despite a normal total calcium level.

Corrected calcium levelOne can derive a corrected calcium (also known as adjusted calcium) level, to allow for the change in total calciumdue to the change in albumin-bound calcium. This gives an estimate of what the total calcium level would be if thealbumin were a specified normal value. Exact formulae used to derive corrected calcium may depend on theanalytical methods used for calcium and albumin. However the traditional method of calculating it is shown below.

Corrected calcium (mg/dL) = measured total Ca (mg/dL) + 0.8 (4.0 - serum albumin [g/dL]), where 4.0represents the average albumin level in g/dL.

in other words, each 1 g/dL decrease of albumin will decrease 0.8 mg/dL in measured serum Ca and thus 0.8 must beadded to the measured Calcium to get a corrected Calcium value.

Or: Corrected calcium (mmol/L) = measured total Ca (mmol/L) + 0.02 (40 - serum albumin [g/L]), where 40represents the average albumin level in g/L

in other words, each 1 g/L decrease of albumin, will decrease 0.02 mmol/L in measured serum Ca and thus 0.02must be added to the measured value to take this into account and get a corrected calcium.When there is hypoalbuminemia (a lower than normal albumin), the corrected calcium level is higher than the totalcalcium.

Effector organs

AbsorptionAbout 25 mmol of calcium enters the body in a normal diet. Of this, about 40% (10 mmol) is absorbed in smallintestine, and 5 mmol leaves the body in feces, netting 5 mmol of calcium a day.[1]

Calcium is absorbed across the intestinal brush border membrane, passing through ion channels such as TRPV6.Calbindin is a vitamin D-dependent calcium-binding protein inside intestinal epithelial cells which functions togetherwith TRPV6 and calcium pumps (PMCA1) in the basal membrane to actively transport calcium into the body.Active transport of calcium occurs primarily in the duodenum portion of the intestine when calcium intake is low;and through passive paracellular transport occurs in the jejunum and ileum parts when calcium intake is high,independent of Vitamin D level.[2]

Calcium metabolism 24

ExcretionThe kidney excretes 250 mmol a day in pro-urine, and resorbs 245 mmol, leading to a net loss in the urine of5 mmol/d. In addition to this, the kidney processes Vitamin D into calcitriol, the active form that is most effective inassisting intestinal absorption. Both processes are stimulated by parathyroid hormone.

The role of boneAlthough calcium flow to and from the bone is neutral, about 5 mmol is turned over a day. Bone serves as animportant storage point for calcium, as it contains 99% of the total body calcium. Calcium release from bone isregulated by parathyroid hormone. Calcitonin stimulates incorporation of calcium in bone, although this process islargely independent of calcitonin.Low calcium intake may also be a risk factor in the development of osteoporosis. In one meta-analysis, the authorsfound that fifty out of the fifty-two studies that they reviewed showed that calcium intake promoted better bonebalance. With a better bone balance, the risk of osteoporosis is lowered.

Interaction with other chemicals

Potential positive interactions• Vitamin D is an important co-factor in the intestinal absorption of calcium, as it increases the number of calcium

binding proteins, involved in calcium absorption through the apical membrane of enterocytes in small intestine. Italso promotes re-absorption of calcium in the kidneys.[citation needed]

• Magnesium also plays an important role in calcium absorption by bones. Release of calcium from thesarcoplasmic reticulum is inhibited by magnesium. Thus hypomagnesemia results in an increased intracellularcalcium level. This inhibits the release of parathyroid hormone, which can result in hypoparathyroidism andhypocalcemia. Furthermore, it makes skeletal and muscle receptors less sensitive to parathyroid hormone. [citation

needed]

• Boron[citation needed]

Potential negative interactions• "Unesterified long-chain saturated fatty acids, i.e. palmitic acid, have a melting point above body temperature

and, with sufficient calcium in the intestinal lumen, form insoluble calcium soaps."• Sodium binding to calcium• Phytic acid binding to calcium• Oxalic acid binding to calcium• Cortisol binding to calcium• Low pH food and proteins (the latter promotes gastric acid)[citation needed]

Calcium metabolism 25

Regulatory organs

Calcium regulation in the human body.[3]

Primarily calcium is regulated by the actions of1,25-Dihydroxycholecalciferol, parathyroid hormone(PTH) and calcitonin and direct exchange with the bonematrix. Plasma calcium levels are regulated byhormonal and non-hormonal mechanisms. Afteringestion of substantial amounts of calcium the shortterm control that prevents calcium spiking in the serumis absorption by the bone matrix. After about an hour,PTH will be released and not peak for about 8 hours.[4]

The PTH is, over time, a very potent regulator ofplasma calcium, and controls the conversion of vitaminD into its active form in the kidney. The parathyroidglands are located behind the thyroid, and produceparathyroid hormone in response to low calcium levels.

The parafollicular cells of the thyroid producecalcitonin in response to high calcium levels, but itssignificance is much smaller than that of PTH.

Pathology

Hypocalcemia and hypercalcemia are both serious medical disorders.Renal osteodystrophy is a consequence of chronic renal failure related to the calcium metabolism.Osteoporosis and osteomalacia have been linked to calcium metabolism disorders.

Research into cancer preventionThe role that calcium might have in reducing the rates of colorectal cancer has been the subject of many studies.However, given its modest efficacy, there is no current medical recommendation to use calcium for cancer reduction.Several epidemiological studies suggest that people with high calcium intake have a reduced risk of colorectalcancer. These observations have been confirmed by experimental studies in volunteers and in rodents. One largescale clinical trial shows that 1.2 g calcium each day reduces, modestly, intestinal polyps recurrence in volunteers.Data from the four published trials are available.[5] Some forty carcinogenesis studies in rats or mice, reported in theChemoprev.Database, also support that calcium could prevent intestinal cancer.[6]

References[1] Barrett KE, Barman SM, Boitano S, Brooks H, "Chapter 23. Hormonal Control of Calcium & Phosphate Metabolism & the Physiology of

Bone" (Chapter). Barrett KE, Barman SM, Boitano S, Brooks H: Ganong's Review of Medical Physiology, 23e: http:/ / www. accessmedicine.com/ content. aspx?aID=5244785.

[2] http:/ / www. vivo. colostate. edu/ hbooks/ pathphys/ digestion/ smallgut/ absorb_minerals. html[3][3] Page 1094 (The Parathyroid Glands and Vitamin D) in:[4][4] Medical Physiology; Guyton, Saunders and Co. 1976pp.1062[5] Potency-Man (http:/ / www. inra. fr/ reseau-nacre/ sci-memb/ corpet/ Data/ table. php?file=Potency-Man. txt)[6] Calcium meta-analysis Colon Cancer chemoprevention systematic review (http:/ / www. inra. fr/ reseau-nacre/ sci-memb/ corpet/

MAcalcium. html)

Calcium metabolism 26

External links• Calcium (http:/ / labtestsonline. org/ understanding/ analytes/ calcium/ tab/ test) at Lab Tests Online• Physiology at MCG 5/5ch6/5ch6line (http:/ / web. archive. org/ web/ 20080401093403/ http:/ / www. lib. mcg.

edu/ edu/ eshuphysio/ program/ section5/ 5ch6/ 5ch6line. htm)

Calcium deficiency

Calcium deficiency (blossom end rot) on atomato

Calcium (Ca) deficiency is a plant disorder that can be caused byinsufficient calcium in the growing medium, but is more frequently aproduct of low transpiration of the whole plant or more commonly theaffected tissue. Plants are susceptible to such localized calciumdeficiencies in low or nontranspiring tissues because calcium is nottransported in the phloem. This may be due to water shortages, whichslow the transportation of calcium to the plant, poor uptake of calciumthrough the stem, or can be caused by excessive usage of potassium ornitrogen fertilizers.[citation needed]

CausesAcidic, sandy, or coarse soils often contain less calcium. Uneven soil moisture and overuse of fertilizers can alsocause calcium deficiency. At times, even with sufficient calcium in the soil, it can be in an insoluble form and is thenunusable by the plant or it could be attributed to a "transport protein".[] Soils containing high phosphorus areparticularly susceptible to creating insoluble forms of calcium.

Symptoms

Blossom end rot on a grape tomato

Calcium deficiency symptoms appear initially as localized tissuenecrosis leading to stunted plant growth, necrotic leaf margins onyoung leaves or curling of the leaves, and eventual death of terminalbuds and root tips. Generally, the new growth and rapidly growingtissues of the plant are affected first. The mature leaves are rarely ifever affected because calcium accumulates to high concentrations inolder leaves.

Crop-specific symptoms include[citation needed]:Apple

'Bitter pit' – fruit skins develop pits, brown spots appear on skinand/or in flesh and taste of those areas is bitter. This usuallyoccurs when fruit is in storage, and Bramley apples areparticularly susceptible. Related to boron deficiency, "watercored" apples seldom display bitter pit effects.

Cabbage and Brussels sproutsInternal browning and "tip burn"

Carrot

Calcium deficiency 27

'Cavity spot' – oval spots develop into craters which may be invaded by other disease-causing organisms.Celery

Stunted growth, central leaves stunted.Tomatoes and peppers

'Blossom end rot' – Symptoms start as sunken, dry decaying areas at the blossom end of the fruit, furthestaway from the stem, not all fruit on a truss is necessarily affected. Sometimes rapid growth from high-nitrogenfertilizers may exacerbate blossom end rot.

Treatment

Dissection of grape tomato with blossom end rot

Calcium deficiency can sometimes be rectified by adding agriculturallime to acid soils, aiming at a pH of 6.5, unless the subject plantsspecifically prefer acidic soil. Organic matter should be added to thesoil to improve its moisture-retaining capacity. However, because ofthe nature of the disorder (i.e. poor transport of calcium to lowtranspiring tissues), the problem cannot generally be cured by theaddition of calcium to the roots. In some species, the problem can bereduced by prophylactic spraying with calcium chloride of tissues atrisk. [citation needed]

Plant damage is difficult to reverse, so corrective action should betaken immediately, supplemental applications of calcium nitrate at 200 ppm nitrogen, for example. Soil pH should betested, and corrected if needed, because calcium deficiency is often associated with low pH. [citation needed]

References• Hopkins, William G., Norman P.A. Hüner. Introduction to Plant Physiology. London: Wiley & Sons, 2009.• Nguyen, Ivy. “Increasing Vitamin D2 with Ergosterol for Calcium Absorption in Sugarcane.” UC Davis

COSMOS. July 2009. 17 October 2010. NGUYEN_IVY.pdf [1]

• Simon, E.W. “The Symptoms of Calcium Deficiency in Plants.” New Phytologist 80 (1978):1-15.

Notes[1] http:/ / cosmos. ucdavis. edu/ archives/ 2009/ cluster1/ NGUYEN_IVY. pdf

External links• Blossom end Rot video (http:/ / www. infoagro. com/ video/ video_agricola. asp?id=16)• Example of blossom end rot on Roma tomatoes (http:/ / tinypic. com/ 6739yo)• Blossom End Rot - symptoms, cause and management (http:/ / ohioline. osu. edu/ hyg-fact/ 3000/ 3117. html) -

The Ohio State University Extension

Article Sources and Contributors 28

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Calcium in biology  Source: http://en.wikipedia.org/w/index.php?oldid=585881363  Contributors: Ajay5150, Amakuha, Arcadian, Arseni, Artichoker, Asiela, Badagnani, Bgwhite, Biochemza,Bryan Derksen, Chris the speller, Clicketyclack, Cnickelfr, Cohesion, Crag, Dcirovic, Delldot, Delldot on a public computer, Delta G, Dlrohrer2003, Drphilharmonic, Dstudent, Eastlaw,Emmanuelm, EryZ, Flying sheep, Frangibility, Gobonobo, Heidiho29, J.delanoy, J04n, Jackbauer115, Jared81, Ka Faraq Gatri, Kai445, Keenan Pepper, Lambiam, Lectonar, Luci Sandor,Ma8thew, Mashin6, Matthew238, Mav, Michael H 34, MichaelWheeley, Mikael Häggström, Mushin, Neøn, Nomad2u001, Ntsimp, Ntudreamer, Nufy8, OwenBlacker, P199, PS2pcGAMER,Petergans, Phlebas, Qxz, RDBrown, Racingstripes, RandomP, Reedy, Rjwilmsi, Samar, Sangak, Scwlong, Sjakkalle, Slarson, Smartse, SteinbDJ, Stewartadcock, Stone, Tony Sidaway, Useight,Vanv2642, Wavelength, Wisdom89, 95 anonymous edits

Calcium metabolism  Source: http://en.wikipedia.org/w/index.php?oldid=586185688  Contributors: Allmightyduck, Apollo1758, Arcadian, Ark7, Arripay, Bensaccount, BrightStarSky, Brim,Bryan Derksen, Corpet, Drcarlos, Dreadstar, Eleassar777, Generic Player, Gildindaimoth, Gobonobo, Headbomb, IONTRANSP, Inferior Olive, Jasonasosa, Jfdwolff, Jimw338, Jonathan.viney,K.nirujan, Lir, LittleHow, MIRROR, Materialscientist, Mikael Häggström, Mike2vil, Moez, MooresLaw, Neøn, Ntsimp, Nutriveg, ObjectivismLover, Pinethicket, R'n'B, RDBrown, RJFJR,Rhombus, Riley Huntley, Rjwilmsi, RoyBoy, Sam Hocevar, Snowolf, Sturders, Theolatic, Thine Antique Pen, Ururu, WQUlrich, WatchAndObserve, Westin, Zmandel, 84 anonymous edits

Calcium deficiency  Source: http://en.wikipedia.org/w/index.php?oldid=584120241  Contributors: (, A13ean, Aaronw, Agarciagrower, BD2412, Bryan Derksen, Bunchofgrapes, C. Ryan Long,Clicketyclack, D6, DadaNeem, Drf5n, Earthdirt, Eug, Excirial, Fred Bradstadt, Headbomb, Heidiho29, HelloMojo, Hephaestos, Heron, Ipatrol, Katharineamy, Kazvorpal, Ketsuekigata,Menthaxpiperita, Mgreenbe, Million Moments, Nominus, PDH, Pinethicket, Pixelface, Quercusrobur, RJFJR, Red58bill, RedGreenInBlue, Rhombus, Sidelight12, SilkTork, Siltloam, Tannin,Teratornis, Tristanb, Widr, 25 anonymous edits

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Image Sources, Licenses and ContributorsFile:Transparent.gif  Source: http://en.wikipedia.org/w/index.php?title=File:Transparent.gif  License: Public Domain  Contributors: Edokterfile:Calcium unter Argon Schutzgasatmosphäre.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Calcium_unter_Argon_Schutzgasatmosphäre.jpg  License: Public Domain Contributors: Matthias Zepperfile:Calcium Spectrum.png  Source: http://en.wikipedia.org/w/index.php?title=File:Calcium_Spectrum.png  License: Creative Commons Attribution-Sharealike 3.0  Contributors:User:AbbybilaninFile:Cubic-face-centered.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Cubic-face-centered.svg  License: GNU Free Documentation License  Contributors: Original PNGs byDaniel Mayer and DrBob, traced in Inkscape by User:StanneredFile:FlammenfärbungCa.png  Source: http://en.wikipedia.org/w/index.php?title=File:FlammenfärbungCa.png  License: Public Domain  Contributors: Jusjih, Red devil 666, Saperaud, 1anonymous editsImage:Pamukkale Hierapolis Travertine pools.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Pamukkale_Hierapolis_Travertine_pools.JPG  License: GNU Free DocumentationLicense  Contributors: PvasiliadisImage:500 mg calcium supplements with vitamin D.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:500_mg_calcium_supplements_with_vitamin_D.jpg  License: GNU FreeDocumentation License  Contributors: RagesossFile:Calcium regulation.png  Source: http://en.wikipedia.org/w/index.php?title=File:Calcium_regulation.png  License: Public Domain  Contributors: Mikael HäggströmFile:Blood values sorted by mass and molar concentration.png  Source: http://en.wikipedia.org/w/index.php?title=File:Blood_values_sorted_by_mass_and_molar_concentration.png  License:Creative Commons Zero  Contributors: Mikael HäggströmImage:Ca-TableImage.png  Source: http://en.wikipedia.org/w/index.php?title=File:Ca-TableImage.png  License: GNU Free Documentation License  Contributors: user:SchneelockeFile:Blossom end rot.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Blossom_end_rot.JPG  License: Creative Commons Attribution-Sharealike 3.0  Contributors: A13eanFile:Blossomendrot.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Blossomendrot.jpg  License: Public Domain  Contributors: SiltloamFile:Blossomrotcloseup.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Blossomrotcloseup.jpg  License: Public Domain  Contributors: Siltloam

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