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From
the American Heritage Dictionary:
SYLLABICATION: cal·ci·um
PRONUNCIATION: AUDIO: kls-m KEY
NOUN: Symbol Ca A silvery, moderately hard metallic
element that constitutes approximately 3 percent of
the earth's crust and is a basic component of most animals
and plants. It occurs naturally in limestone, gypsum,
and fluorite, and its compounds are used to make plaster,
quicklime, Portland cement, and metallurgic and electronic
materials. Atomic number 20; atomic weight 40.08; melting
point 842 to 848°C; boiling point 1,487°C; specific
gravity 1.55; valence 2. See table at element.
ETYMOLOGY: Latin calx, calc-, lime; see calx + –ium.
What
is Calcium and what is it's function in the human body?
Calcium (symbol: Ca) is one of the alkaline earth
metals that comprise the
Group IIA or S2 elements of the periodic table. The
electronic
configuration of calcium (atomic number: 20) is 1S2;2S22P6;3S23P6;4S2.
The physical constants
of calcium are as follows:
1. Atomic mass : 40.08
2. Atomic radius : 1.74 A0
3. Ionic radius : 0.99 A0
4. Density : 1.60 g/cm3
5. Melting point : 1116 K
6. Ionisation energy (KJ/mol) : I stage 590
II stage 1146
7. Electronegativity : 1.04
8. Flame coloration : Brick red
9. Oxidation state : +2
10. Abundance in earth's crust (ppm) : 3.0 x 10(4)
Calcium is extracted by the electrolysis
of a fused mixture of anhydrous
calcium chloride and potassium chloride using iron cathode
and graphite
anode.
Calcium being a powerful reducing
agent is used in extraction of metals
from oxides which are difficult to reduce with carbon.
It is also used for
removing last traces of dissolved oxygen, nitrogen and
sulfur from metals
in the course of their extraction. Important compounds
of calcium are calcium oxide, calcium hydroxide, calcium
chloride, calcium sulfate (gypsum), and plaster of Paris.
Calcium helps build and maintain
strong bones and teeth, thus protecting
against osteoporosis. It plays a role in nerve conduction,
muscle
contraction and blood clotting. Calcium also appears
to regulate blood
pressure and may help lower the risk for colon cancer.
Calcium helps muscle contraction
(including in the heart) by allowing
proteins found in muscles (called actin and myosin)
to interact properly.
By participating in the synthesis of fibrin, calcium
makes it possible for
blood clots to form.
Calcium affects the release of
neurotransmitters.
Calcium regulates cell metabolism,
including glycogen synthesis (the
process by which glucose is converted into glycogen).
Calcium can bind free
fatty acids and bile acids, which irritate the colon.
This irritation may
increase cell development to the point of increasing
the risk of cancers.
In adults, osteomalacai and/or osteoporosis (fragile,
brittle bones that
fracture under normal use) can result from calcium deficiency.
In addition,
loss of height and premature tooth loss may exist.
If blood calcium levels are low
(hypocalcemia), muscles cannot relax
following a contraction, resulting in tetany. Symptoms
of tetany include
muscle spasms and leg cramps. In children, the deficiency
disease, rickets,
leads to stunted growth and bone deformities.
The adult body contains approximately
1200g of calcium, ~99% of which is
present in the skeleton. The remaining 1% of body calcium
is found in the
extracellular fluid, intracellular structures and cell
membranes.
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