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-abundant dissolved ion in seawater by both molarity and mass, after sodium, chloride, magnesium, and sulfate.

Calcium, with a density of 1. 55 g / cm < sup > 3 </ sup >, is the lightest of the alkaline earth metals ; magnesium ( specific gravity 1. 74 ) and beryllium ( 1. 84 ) are more dense, although lighter in atomic mass.

Calcium has a higher electrical resistivity than copper or aluminium, yet weight-for-weight, due to its much lower density, it is a rather better conductor than either.

Calcium is the fifth-most-abundant element by mass in the human body, where it is a common cellular ionic messenger with many functions, and serves also as a structural element in bone.

Calcium, combined with phosphate to form hydroxylapatite, is the mineral portion of human and animal bones and teeth.

Calcium hydroxide ( slaked lime ) is used in many chemical refinery processes and is made by heating limestone at high temperature ( above 825 ° C ) and then carefully adding water to it.

Calcium carbonate ( CaCO < sub > 3 </ sub >) is one of the common compounds of calcium.

Calcium is not naturally found in its elemental state.

Calcium is used

* Calcium carbonate ( CaCO < sub > 3 </ sub >) is used in manufacturing cement and mortar, lime, limestone ( usually used in the steel industry ) and aids in production in the glass industry.

* Calcium hydroxide solution ( Ca ( OH )< sub > 2 </ sub >) ( also known as limewater ) is used to detect the presence of carbon dioxide by being bubbled through a solution.

* Calcium arsenate ( Ca < sub > 3 </ sub >( AsO < sub > 4 </ sub >)< sub > 2 </ sub >) is used in insecticides.

* Calcium carbide ( CaC < sub > 2 </ sub >) is used to make acetylene gas ( for use in acetylene torches for welding ) and in the manufacturing of plastics.

* Calcium chloride ( CaCl < sub > 2 </ sub >) 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 cyclamate ( Ca ( C < sub > 6 </ sub > H < sub > 11 </ sub > NHSO < sub > 3 </ sub >)< sub > 2 </ sub >) was used as a sweetening agent but is no longer permitted for use because of suspected cancer-causing properties.

* Calcium gluconate ( Ca ( C < sub > 6 </ sub > H < sub > 11 </ sub > O < sub > 7 </ sub >)< sub > 2 </ sub >) is used as a food additive and in vitamin pills.

* Calcium hypochlorite ( Ca ( OCl )< sub > 2 </ sub >) is used as a swimming pool disinfectant, as a bleaching agent, as an ingredient in deodorant, and in algaecide and fungicide.

* Calcium permanganate ( Ca ( MnO < sub > 4 </ sub >)< sub > 2 </ sub >) is used in liquid rocket propellant, textile production, as a water sterilizing agent and in dental procedures.

* Calcium phosphate ( Ca < sub > 3 </ sub >( PO < sub > 4 </ sub >)< sub > 2 </ sub >) 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.

Many elements are essential to humans ' survival, such as Calcium being what forms bones.

Calcium ions are essential for binding of these coagulation factors.

Calcium hydride was substituted for Af as a drying agent for carbon tetrachloride.

Calcium has four stable isotopes (< sup > 40 </ sup > Ca, < sup > 42 </ sup > Ca, < sup > 43 </ sup > Ca and < sup > 44 </ sup > Ca ), plus two more isotopes (< sup > 46 </ sup > Ca and < sup > 48 </ sup > Ca ) that have such long half-lives that for all practical purposes they also can be considered stable.

* Calcium levels in livestock feed are supplemented with it, such as for poultry ( when ground up ).

* Calcium, a common electrolyte, but also needed structurally ( for muscle and digestive system health, bone strength, some forms neutralize acidity, may help clear toxins, provides signaling ions for nerve and membrane functions )

Calcium oxide, in the form of lime, was often used for this purpose, since it could react with the carbon dioxide and sulfur dioxide produced during roasting and smelting to keep them out of the working environment.

Calcium channel blockers and losartan are associated with a lower risk of gout as compared to other medications for hypertension.

Calcium for egg development-another hypothesis-does not appear to be a reason for geophagy during this period as peak usage is after the hatching of eggs.

Calcium ( Ca ) is in group 2, for it contains 2 valence electrons.

Calcium was needed for agricultural, pharmaceutical and paint products.

Historic landmarks include the stone house at the intersection of State Route 342 and County Route 138 that once served as the post office for the area, and the Calcium Community Church at the same intersection.

Calcium is known to be a treatment for gastric problems, and gastric problems such as acid reflux are known to increase bruxism.

“ Increasing Vitamin D2 with Ergosterol for Calcium Absorption in Sugarcane .” UC Davis COSMOS.

Calcium ions are required for each cycle of the sarcomere.

Calcium carbonate is used by living organisms to manufacture carbonaceous tests and shells.

Calcium ( Ca < sup > 2 +</ sup >) plays a pivotal role in the physiology and biochemistry of organisms and the cell.

By combining the chemistry of a particular product ( CCE ) and its particle size the Effective Calcium Carbonate Equivalent ( ECCE ) is determined. The ECCE is percentage comparison of a particular agricultural limestone with pure calcium carbonate with all particles smaller than 60 mesh. Typically the aglime materials in commercial use will have ECCE ranging from 45 percent to 110 percent.

Calcium is used in many processes including muscle contraction, neurotransmitter release from nerve endings and cell migration.

Calcium is removed from the muscle cell cytoplasm independent of repolarization ( depolarization signaling and muscle contraction are independent processes ).

The phosphorylation events lead to a decrease in intracelluar calcium ( inhibit L type Calcium channels, inhibits IP3 receptor channels, stimulates sarcoplasmic reticulum Calcium pump ATPase ), a decrease in the 20kd myosin light chain phosphorylation by altering calcium sensitization and increasing myosin light chain phosphatase activity, a stimulation of calcium sensitive potassium channels which hyperpolarize the cell, and the phosphorylation of amino acid residue serine 16 on the small heat shock protein ( hsp20 ) by Protein Kinases A and G. The phosphorylation of hsp20 appears to alter actin and focal adhesion dynamics and actin-myosin interaction, and recent evidence indicates that hsp20 binding to 14-3-3 protein is involved in this process.

The cleavage furrow mechanism in animal cells is a complex network of actin and myosin filaments, Golgi vesicles and Calcium dependent channels enabling the cell to break apart, reseal and form new daughter cells with complete membranes.

Calcium is, therefore, a cell signaling molecule, and not usually considered a cofactor of the enzymes it regulates.

Calcium, which plays many roles in the cell and is tightly regulated, disrupts the membrane when it appears in excess.

Calcium ions flow into the cell causing a depolarization.

This inhibition of voltage-gated Calcium channels by G protein-coupled receptors has been demonstrated in the dorsal root ganglion of a chick among other cell lines.

Calcium ions play an important role in cell signaling, especially with regards to the ER.

Calcium entry into the cell causes more prolonged depolarization and increased action potentials.