Copper

Biological functions

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Native Cu. Image: Wikimedia, Jonathan Zander

The mineral copper is a chemical element (chemical symbol Cu). Its atomic weight is 63.546, and atomic number, 29. Cu is an essential nutrient because the body has to have copper to function. Only trace amounts of it are needed, but not getting enough (or getting too much) can pose health risks.

Cu proteins have various roles in biological electron transport and oxygen transportation. Cu aids tissue respiration and the synthesis of cytochrome and is required in small amounts by all plants and animals. Its salts, however, are poisonous.

Normally, the human body contains about 1.4 to 2.1 mg of Cu for each kilogram of body weight. In the diet it is absorbed via the consumption of various plant and animal tissues. Found throughout the body, Cu is found at higher levels in the liver. It is also present in many enzymes, including cytochrome c oxidase and superoxide dismutase. Another function is in the transformation of iron into hemoglobin. Cu is excreted by the kidneys.

Symptoms of deficiency include anemia (due to poor utilization of iron in the production of hemoglobin) and resulting weakness, as well as impaired growth and respiration. There seems to be no evidence, however, that people who eat a normal diet need supplements of this element.

Horseshoe crab Credit: Wikimedia

For oxygen transport, most mollusks and certain arthropods, such as the horseshoe crab (Limulus polyphemus), use the pigment hemocyanin, contains Cu, instead of hemoglobin. As a result, their blood is blue-green, not red, when oxygenated. In such organisms the hemocyanin is circulated in the hemolymph.

Dietary sources

Excellent sources of Cu in the diet include beef and lamb liver, cocoa, avocados, oysters, lobster, nuts (especially Brazil nuts), wheat bran, green olives, molasses and black pepper.

Though formerly used widely as an emetic, Cu₄SO₄ is now generally considered too toxic for that application. Symptoms of poisoning by Cu₄SO₄ include an unpleasant, metallic taste, tightness of the throat, thirst, vomiting, and stomach pain.

Copper sulphate (Cu₄SO₄)

Though formerly used widely as an emetic, Cu₄SO₄ is now generally considered too toxic for that application. Symptoms of poisoning by Cu₄SO₄ include an unpleasant, metallic taste, tightness of the throat, thirst, vomiting, and stomach pain.

Prefixes

The prefixes chalc and chalco refer to this element. Thus, the first stage of the Bronze Age, which preceded the discovery that adding tin to Cu produced a superior alloy, is known as the Chalcolithic. Chronic Cu poisoning is known as chalcosis (note, however, that chalicosis is a lung disease resulting from the inhalation of airborne stone particles). Chalcanthite is a mineral composed of native Cu₄SO₄, and chalcocite, one consisting of native cuprous sulfide (Cu₂S).

PERIODIC TABLE

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