<P> Until the late nineteenth century, sugar was purchased in loaves, which had to be cut using implements called sugar nips . In later years, granulated sugar was more usually sold in bags . Sugar cubes were produced in the nineteenth century . The first inventor of a process to make sugar in cube form was the Moravian Jakub Kryštof Rad, director of a sugar company in Dačice . He began sugar cube production after being granted a five - year patent for the process on January 23, 1843 . Henry Tate of Tate & Lyle was another early manufacturer of sugar cubes at his refineries in Liverpool and London . Tate purchased a patent for sugar cube manufacture from German Eugen Langen, who in 1872 had invented a different method of processing of sugar cubes . </P> <P> Scientifically, sugar loosely refers to a number of carbohydrates, such as monosaccharides, disaccharides, or oligosaccharides . Monosaccharides are also called "simple sugars," the most important being glucose . Most monosaccharides have a formula that conforms to C nH 2n O n with n between 3 and 7 (deoxyribose being an exception). Glucose has the molecular formula C 6H 12 O 6 . The names of typical sugars end with - ose, as in "glucose" and "fructose". Sometimes such words may also refer to any types of carbohydrates soluble in water . The acyclic mono - and disaccharides contain either aldehyde groups or ketone groups . These carbon - oxygen double bonds (C = O) are the reactive centers . All saccharides with more than one ring in their structure result from two or more monosaccharides joined by glycosidic bonds with the resultant loss of a molecule of water (H 2O) per bond . </P> <P> Monosaccharides in a closed - chain form can form glycosidic bonds with other monosaccharides, creating disaccharides (such as sucrose) and polysaccharides (such as starch). Enzymes must hydrolyze or otherwise break these glycosidic bonds before such compounds become metabolized . After digestion and absorption the principal monosaccharides present in the blood and internal tissues include glucose, fructose, and galactose . Many pentoses and hexoses can form ring structures . In these closed - chain forms, the aldehyde or ketone group remains non-free, so many of the reactions typical of these groups cannot occur . Glucose in solution exists mostly in the ring form at equilibrium, with less than 0.1% of the molecules in the open - chain form . </P> <P> Biopolymers of sugars are common in nature . Through photosynthesis, plants produce glyceraldehyde - 3 - phosphate (G3P), a phosphated 3 - carbon sugar that is used by the cell to make monosaccharides such as glucose (C 6H 12 O 6) or (as in cane and beet) sucrose (C 12 H 22 O 11). Monosaccharides may be further converted into structural polysaccharides such as cellulose and pectin for cell wall construction or into energy reserves in the form of storage polysaccharides such as starch or inulin . Starch, consisting of two different polymers of glucose, is a readily degradable form of chemical energy stored by cells, and can be converted to other types of energy . Another polymer of glucose is cellulose, which is a linear chain composed of several hundred or thousand glucose units . It is used by plants as a structural component in their cell walls . Humans can digest cellulose only to a very limited extent, though ruminants can do so with the help of symbiotic bacteria in their gut . DNA and RNA are built up of the monosaccharides deoxyribose and ribose, respectively . Deoxyribose has the formula C 5H 10 O 4 and ribose the formula C 5H 10 O 5 . </P>

The most common structure of sugars in solution is