Carbohydrates

Carbohydrates are defined chemically, not just by taste: they are polyhydroxy aldehydes or ketones, or compounds that yield such polyhydroxy carbonyl units on hydrolysis. Some carbohydrates -- glucose, fructose and others -- taste sweet and are informally called sugars; the most familiar sugar, sucrose (table sugar), is obtained from sugarcane or sugar beet, while the sugar naturally present in milk is lactose. The name 'carbohydrate' itself has a historical chemical origin: the molecular formula of many carbohydrates can be written as Cx(H2O)y, literally 'hydrates of carbon' -- for example glucose, C6H12O6, can be written C6(H2O)6; sucrose, C12H22O11, as C12(H2O)11; and starch, (C6H10O5)n, as [C6(H2O)5]n. Because the Greek word for sugar is 'sakkharon', carbohydrates are also called saccharides, a name that recu …