Calcium

Calcium is a chemical element with the symbol Ca and atomic number 20. It is an alkaline earth metal and is the fifth most abundant element by mass in the Earth's crust. Calcium is essential for living organisms, particularly in cell physiology, where movement of the calcium ion Ca²⁺ into and out of the cytoplasm functions as a signal for many cellular processes.

Properties

Calcium is a soft gray metal that is an essential constituent of teeth and bones. It is the fifth most abundant element in the human body and the most abundant metal by mass in many animals. Calcium ions play a vital role in the physiology and biochemistry of organisms and cells, particularly in signal transduction pathways, where they act as a second messenger, in neurotransmitter release from neurons, in contraction of all muscle cell types, and in fertilization.

Occurrence

Calcium does not occur naturally in its elemental state but is found in various minerals such as calcite, dolomite, and gypsum. It is also a major component of limestone, which is used in the production of cement and concrete.

Biological Role

Calcium is crucial for many physiological functions. It is a key component of bone and tooth structure, where it is present as calcium phosphate in the form of hydroxyapatite. Calcium ions are also important in blood clotting, muscle contraction, and nerve function.

Bone Health

Calcium is stored in bones and teeth, where it supports their structure and hardness. The body needs calcium to maintain strong bones and to carry out many important functions. About 99% of the calcium in the body is in bones and teeth. The remaining 1% is found in blood, muscle, and other tissues.

Cellular Functions

Calcium ions play a crucial role in many cellular processes. They are involved in the release of neurotransmitters at synapses, the contraction of muscle cells, and the regulation of enzyme activity. Calcium ions also act as a second messenger in many signal transduction pathways.

Dietary Sources

Calcium can be obtained from various dietary sources. Dairy products such as milk, cheese, and yogurt are rich in calcium. Other sources include leafy green vegetables, nuts, and fish with edible bones such as sardines and salmon.

Deficiency

A deficiency in calcium can lead to various health issues, including osteoporosis, a condition characterized by weak and brittle bones. Symptoms of calcium deficiency include muscle cramps, numbness, and tingling in the fingers, and abnormal heart rhythms.

Supplementation

Calcium supplements are available for individuals who do not get enough calcium from their diet. These supplements come in various forms, including calcium carbonate and calcium citrate. It is important to take calcium supplements as directed by a healthcare provider to avoid potential side effects such as kidney stones.

See Also

• Magnesium
• Phosphorus
• Vitamin D
• Bone mineral density
• Parathyroid hormone