SUGARS (OF., Fr. more, from ME. sucearunt, saccharam, from (;k. mikxap, sakehar, aaK,Iapov, sakcharon, sugar, from Ar. sakkur, from Pers. shukur, shafrkar, from Prak. sakkara, sugar, from Skt. izt-karu, candied sugar, gravel, grit). A term applied to various substances composed of carbon, hydrogen, and oxygen (see CAR110 HYDRATES ), which are more or less sweet, are readily soluble in water, are colorless and odor less, and are usually crystallizable. They are widely distributed in nature as original products of vital processes in plants. They have an un paralleled importance in the organic world. In green plants they are formed from carbon diox ide and water by the chloroplasts (see PHOTO SYNTHESIS ) , and are transferred by diffusion to all parts of the plant body to be used directly in the metabolism of the plant for the manufacture of proteid substances, or to be stored for future use, sometimes as glucose (e.g. in the onion bulb), sometimes as saccharose (e.g. in the beet), and sometimes as other widely different substan ces into which they have been converted. (See
STORAGE.) If formed more rapidly than they can diffuse away, sugars may be condensed into starch in the chloroplasts themselves. At times of renewed growth, as in the germination of seeds and the sprouting of tubers and bulbs, the plant draws upon these stores of carbohydrate. If the storage has been in the form of cellulose, starch, inulin, or cane sugar, the stored food must be converted by means of enzymes into a hexose sugar before it can be utilized. The stored sugars of plant tissues form one of the most valuable sources of animal food.
Sugars found in the bodies of animals or in the excreta therefrom are believed to be derived from substances of vegetable origin. The sugars have been variously classified according to their chemical and physical properties as fermentable and non-fermentable; reducing and non-reducing; and dextro-rotary. heyo-rotary, and inactive, ac cording to their effect on polarized light.