- A nonmetallic tetravalent element, atomic no. 6, atomic wt. 12.011; the major bioelement. It has two natural isotopes, 12C and 13C (the former, set at 12.00000, being the standard for all molecular weights), and two artificial, radioactive isotopes of interest, 11C and 14C. The element occurs in three pure forms (diamond, graphite, and in the fullerines), in amorphous form (in charcoal, coke, and soot), and in the atmosphere as CO2. Its compounds are found in all living tissues, and the study of its vast number of compounds constitutes most of organic chemistry. [L. carbo, coal]- active c. dioxide, activated c. dioxide complex of N-carboxybiotin (biotin + CO2) and an enzyme; the form in which c. dioxide is added to other molecules in carboxylations; e.g., to methylcrotonyl-CoA to form β-methylglutaconyl in the catabolism of leucine, and to acetyl-CoA to form malonyl-CoA. SEE ALSO: acetyl-CoA carboxylase.- c. dioxide CO2; the product of the combustion of c. with an excess of air; in concentrations not less than 99.0% by volume of CO2, used as a respiratory stimulant. SYN: carbonic acid gas, carbonic anhydride.- c. dioxide snow solid c. dioxide used in the treatment of warts, lupus, nevi, and other skin affections, and as a refrigerant. SYN: dry ice.- c. disulfide an extremely flammable (flashpoint −30°C), colorless, toxic liquid with a characteristic ethereal odor (fetid when impure); it is a parasiticide. SYN: c. bisulfide.- c. monoxide (CO) a colorless, practically odorless, and poisonous gas formed by the incomplete combustion of c.; its toxic action is due to its strong affinity for hemoglobin, myoglobin, and the cytochromes, reducing oxygen transport and blocking oxygen utilization.- c. tetrachloride a colorless, mobile liquid having a characteristic ethereal odor resembling that of chloroform; it is used as a cleansing fluid and as a fire extinguisher, and has been used as an anthelmintic, especially against hookworm. SYN: tetrachloromethane.
* * *car·bon 'kär-bən n, often attrib a nonmetallic element found native (as in diamonds and graphite) or as a constituent of coal, petroleum, asphalt, limestone, and organic compounds or obtained artificially (as in activated charcoal) symbol C see ELEMENT (table)
* * *car·bon (C) (kahrґbən) [L. carbo charcoal] a nonmetallic tetrad element, found nearly pure in the diamond, and approximately pure in charcoal, graphite, and anthracite; atomic number 6, atomic weight 12.011. The two naturally occurring, stable isotopes are 12C (98.89 per cent) and 13C (1.11 per cent).
Medical dictionary. 2011.