chloroform Clear, colourless, heavy, nonflammable liquid organic compound with a pleasant etherlike odour, chemical formula CHC1 3 . It was the first substance successfully used as a surgical anesthetic (1847); being somewhat toxic, it has been increasingly displaced by other sub¬ stances for this purpose. It has some industrial uses, primarily as a solvent.
chlorophyll Any member of one of the most important classes of pig¬ ment molecules involved in photosynthesis. Found in almost all photosyn¬ thetic organisms, it consists of a central magnesium atom surrounded by a nitrogen-containing structure called a porphyrin ring, to which is attached a long carbon-hydrogen side chain, known as a phytol chain. In structure it is remarkably similar to hemoglobin. Chlorophyll uses energy that it absorbs from light to convert carbon dioxide to carbohydrates. In higher plants it is found in chloroplasts.
chloroplast Microscopic, ellipsoidal organelle in a green plant cell. It is the site of photosynthesis. It is distinguished by its green colour, caused by the presence of chlorophyll. It contains disk-shaped structures called thylakoids that make possible the formation of ATP, an energy-rich stor¬ age compound.
Internal structures of the chloroplast. The interior contains flattened sacs of photo¬ synthetic membranes (thylakoids) formed by the invagination and fusion of the inner membrane. Thylakoids are usually arranged in stacks (grana) and contain the photosynthetic pigment (chlorophyll). The grana are connected to other stacks by simple membranes (lamellae) within the stroma, the fluid proteinaceous portion con¬ taining the enzymes essential for the photosynthetic dark reaction, or Calvin cycle.
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Chlotar \'klo-,tar\ I (b. c. 500?—d. late 561, Compiegne, Fr.) Merov¬ ingian king of Soissons from 511 and of the whole Frankish kingdom from 558. (See Merovingian dynasty.) The youngest son of Clovis I, he shared in the partition of his father’s kingdom in 511 and extended his lands by murder and intrigue. He launched campaigns against the Burgundians (523, 532-34), the Visigoths (532, 542), and the Thuringians (c. 531). A ruthless and brutal ruler, Chlotar put to death his rebellious son Chram with his family (560).
Chobe Vcho-ba\ National Park National preserve, northern Botswana. The preserve, which acquired national park status in 1968, borders Namibia and touches Zimbabwe and Zambia, covering 4,500 sq mi (11,700 sq km). It is noted for its wildlife, particularly its large elephant population.
chocolate Food prepared from ground roasted cacao beans. It is con¬ sumed as candy, used to make beverages, and added as a flavouring or coating for confections and baked products. It was introduced to Europe by Hernan Cortes following his visit in 1519 to the court of Montezuma
II. who served the conquistador a bit¬ ter cacao-bean drink, xocoatl. In making chocolate, the kernels of fer¬ mented and roasted cacao beans are ground into a paste called chocolate liquor, which may be hardened in molds to form baking (bitter) choco¬ late, pressed to reduce the cocoa but¬ ter (vegetable fat) content and then pulverized to make cocoa powder, or mixed with sugar and additional cocoa butter to make sweet (eating) chocolate. The addition of concen¬ trated milk to sweet chocolate pro¬ duces milk chocolate. White chocolate, made from cocoa butter, sugar, milk, and vanilla, contains no cocoa solids. Rich in carbohydrates and fat and containing small amounts of caffeine, chocolate is an excellent source of quick energy.
Choctaw North American Indian people living in Oklahoma, U.S. They speak a Muskogean language that is closely related to that of the Chick¬ asaw. The Choctaw once lived in what is now southeastern Mississippi. They were the most skillful of the southeastern farmers, usually having surplus produce to sell or trade. They fished, gathered nuts and wild fruits, hunted deer and bear, and planted com, beans, and pumpkins. Their prin¬ cipal religious ceremony was the Busk (Green Corn) festival, a first-fruits and new-fire rite celebrated at midsummer. In the 19th century, pressure by white cotton-growers forced them to cede five million acres, and most Choctaw were removed to Oklahoma. Some 87,300 individuals claimed sole Choctaw descent in the 2000 U.S. census.
Ch'oe Si-hydng Vchoe-’se-'yoqV (b. 1827, Korea—d. 1898, Seoul) Sec¬ ond leader of the Korean Tonghak (now Ch'ondogyo) religion. He orga¬ nized the underground network that spread the apocalyptic, antiforeign Tonghak sect following the execution of its founder, Ch’oe Che-u (1824- 64). He published the first two Tonghak scriptures in 1880 and 1881, add¬ ing public service to the founder’s principle of human equality and obligation to serve heaven. Preaching the need for Korea to become as strong as Western imperialist powers, in 1894 he led the Tonghak Upris¬ ing, which was viciously suppressed. He was arrested and executed in 1898, by which time Tonghak had spread throughout Korea.
choir Body of singers with more than one voice to a part. For many cen¬ turies, church choirs sang only plainsong (see Gregorian chant). The rela¬ tive complexity of early polyphony required solo voices rather than choral performance, but by the 15th century polyphony was being performed chorally. The growth of the secular choir (or chorus) coincided with the beginnings of opera. An oratorio choir is part of a different tradition, which stems from the augmented church choirs used to provide choral portions of a given oratorio, whether performed in or out of church.
Choiseul \shwa-'z3l\, Etienne-Francois de Choiseul, duke de
(b. June 28, 1719, Lorraine, France—d. May 8, 1785, Paris) French for¬ eign minister. He served with distinction in the War of the Austrian Suc¬ cession. After serving as ambassador to the Vatican (1753-57) and to the Austrian court, he was made a duke and named minister of foreign affairs (1758), in which position he came to dominate the government of Louis XV. In 1761 he concluded a military alliance with Spain (the “Family Compact”), and at the end of the Seven Years’ War he negotiated the best terms for a defeated France. He rebuilt France’s military strength but was dismissed from office in 1770 for advocating war against Britain.
chokecherry One of several varieties of shrub or small tree (.Prunus virginiana ) of the rose family, native to North America. Though it is aptly named for the astringent, acidic taste of its reddish cherries, its fruit may be made into jelly and preserves. The stones and wilted foliage are poi¬ sonous. The trees often form dense thickets on moist soils. They are fre¬ quently attacked and defoliated by eastern tent caterpillars. Foul-scented white flowers are produced in hanging spikes, and the slender brown twigs also have an unpleasant odour and a bitter taste.
cholera Vka-b-roX Acute bacterial infection with Vibrio cholerae, caus¬ ing massive diarrhea with severe depletion of body fluids and salts. (See bacterial disease.) Cholera often occurs in epidemics, spreading in con-
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398 I cholesterol ► chorale
taminated water or food. The bacteria secrete a toxin that causes the diar¬ rhea, which along with vomiting leads to dehydration, with severe muscle cramps and intense thirst. Stupor and coma may precede death by shock. With fluid and salt replacement, the disease passes in two to seven days, sooner if antibiotics are taken the first day. Prevention requires good sani¬ tation, especially clean drinking water.
cholesterol Waxy organic compound found in blood and all animal tis¬ sues. It is a steroid, with molecular formula C 27 H 46 0, containing four rings in its structure. Cholesterol is essential to life; it is a primary com¬ ponent of CELL membranes and a starting or intermediate material from which the body makes bile acids, other steroid hormones, and vitamin D. It is made in the liver and some other organs, in greater or lesser amounts depend¬ ing on the amount recently consumed in the diet. It circulates in the blood in compounds called lipoproteins, since it is not water-soluble alone. Excess cholesterol in the blood forms deposits in arteries (see arterioscle¬ rosis), which can lead to coronary heart disease. Michael Brown (born 1941) and Joseph Goldstein (bom 1940) won a Nobel Prize in 1985 for their work in discovering this process. Since the body makes cholesterol from FATS, blood cholesterol cannot be reduced by limiting only the amount of cholesterol in the diet; the amount of fat, especially saturated fat (see saturation, fatty acid) must also be reduced. See also triglyceride.