| Abstract from DBPedia | In organic chemistry, a carbohydrate (/ˌkɑːrboʊˈhaɪdreɪt/) is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula Cm(H2O)n (where m may or may not be different from n), which does not mean the H has covalent bonds with O (for example with CH2O, H has a covalent bond with C but not with O). However, not all carbohydrates conform to this precise stoichiometric definition (e.g., uronic acids, deoxy-sugars such as fucose), nor are all chemicals that do conform to this definition automatically classified as carbohydrates (e.g. formaldehyde and acetic acid). The term is most common in biochemistry, where it is a synonym of saccharide (from Ancient Greek σάκχαρον (sákkharon) 'sugar'), a group that includes sugars, starch, and cellulose. The saccharides are divided into four chemical groups: monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Monosaccharides and disaccharides, the smallest (lower molecular weight) carbohydrates, are commonly referred to as sugars. While the scientific nomenclature of carbohydrates is complex, the names of the monosaccharides and disaccharides very often end in the suffix -ose, which was originally taken from glucose (from Ancient Greek γλεῦκος (gleûkos) 'wine, must'), and is used for almost all sugars, e.g. fructose (fruit sugar), sucrose (cane or beet sugar), ribose, lactose (milk sugar), etc. Carbohydrates perform numerous roles in living organisms. Polysaccharides serve as an energy store (e.g. starch and glycogen) and as structural components (e.g. cellulose in plants and chitin in arthropods). The 5-carbon monosaccharide ribose is an important component of coenzymes (e.g. ATP, FAD and NAD) and the backbone of the genetic molecule known as RNA. The related deoxyribose is a component of DNA. Saccharides and their derivatives include many other important biomolecules that play key roles in the immune system, fertilization, preventing pathogenesis, blood clotting, and development. Carbohydrates are central to nutrition and are found in a wide variety of natural and processed foods. Starch is a polysaccharide and is abundant in cereals (wheat, maize, rice), potatoes, and processed food based on cereal flour, such as bread, pizza or pasta. Sugars appear in human diet mainly as table sugar (sucrose, extracted from sugarcane or sugar beets), lactose (abundant in milk), glucose and fructose, both of which occur naturally in honey, many fruits, and some vegetables. Table sugar, milk, or honey are often added to drinks and many prepared foods such as jam, biscuits and cakes. Cellulose, a polysaccharide found in the cell walls of all plants, is one of the main components of insoluble dietary fiber. Although it is not digestible by humans, cellulose and insoluble dietary fiber generally help maintain a healthy digestive system by facilitating bowel movements. Other polysaccharides contained in dietary fiber include resistant starch and inulin, which feed some bacteria in the microbiota of the large intestine, and are metabolized by these bacteria to yield short-chain fatty acids.炭水化物（たんすいかぶつ、英: carbohydrates、独: Kohlenhydrate）または糖質（とうしつ、仏: glucides、英: saccharides）は、単糖を構成成分とする有機化合物の総称である。非常に多様な種類があり、天然に存在する有機化合物の中で量が最も多い。有機栄養素のうち炭水化物、たんぱく質、脂肪は、多くの生物種で栄養素であり、「三大栄養素」とも呼ばれている。 栄養学上は炭水化物は糖質と食物繊維の総称として扱われており、消化酵素では分解できずエネルギー源にはなりにくい食物繊維を除いたものを糖質と呼んでいる。三大栄養素のひとつとして炭水化物の語を用いるときは、主に糖質を指す。 炭水化物の多くは分子式が CmH2nOn で表され、Cm(H2O)n と表すと炭素に水が結合した物質のように見えるため炭水化物と呼ばれ、かつては含水炭素とも呼ばれた。後に定義は拡大し、炭水化物は糖およびその誘導体やの総称となり、分子式 CmH2nOn で表されない炭水化物もある。そのような例としてデオキシリボース C5H10O4 、ポリアルコール、ケトン、酸などが挙げられる。また、分子式が CmH2nOn ではあっても、ホルムアルデヒド (CH2O, m = n = 1) は炭水化物とは呼ばれない。今日では総称として糖質ないしは糖とよばれる場面の方が多くなっている。 生物に必要不可欠な物質であり、骨格形成、貯蔵、代謝等に広く用いられる。栄養学的あるいはエネルギー代謝以外の糖質の事項については（例えば、化学的、分子生物学的性質）記事 糖に詳しい。 炭水化物は主に植物の光合成でつくられる。 (Source: http://dbpedia.org/resource/Carbohydrate) |
