These two isomers differ in their orientation of OH on C #1 (shown in red in Figure 3.2). Glucose can exist as α and β isomers and has immense animal nutritional implications. Galactose is found along with disaccharide lactose in mammalian milk and is released during digestion. Fructose, or “fruit sugar,” is found in ripened fruits and honey and is also formed by digestion of disaccharide sucrose. Glucose is the form of carbohydrates found in circulating blood (blood sugar) and is the primary carbohydrate used by the body for energy production.
In a biological system, glucose exists primarily as a cyclic form and very rarely in a straight form (in aqueous solution). The chemical structure of glucose can be represented as a straight chain form (Figure 3.1) and in cyclic form (also shown in Figure 3.1). Most nutritionally important sugars are pentoses or hexoses.
Hexose (6 C e.g., glucose, fructose, galactose, and mannose). The following list shows the prefixes for numbers of carbons in a sugar. Monosaccharides can be subdivided based on the number of carbon (C) atoms. Monosaccharides are often referred to as simple sugars (e.g., glucose) and cannot be hydrolyzed into simpler compounds. Based on the number of molecules of sugar in the compound, carbohydrates can be classified as (1) monosaccharide, one unit of sugar (2) disaccharide, two monosaccharides (3) oligosaccharide, three to fifteen monosaccharides and (4) polysaccharides, large polymers of simple sugars.Ī. The suffix “ ose” at the end of a biochemical name flags the molecule as a “sugar.” Among these, pentoses (e.g., ribose in ribonucleic acid (RNA)) and hexoses (e.g., glucose, or blood sugar) are the most common sugars in animal tissues. Based on the number of carbon atoms, a carbohydrate can be classified as triose (3 C), tetrose (4 C), pentose (5 C), and hexose (6 C). One method of classifying carbohydrates is based on the number of carbon atoms per each molecule of a carbohydrate and on the number of molecules of sugar in the compound. Animal metabolism produces energy in a reverse process to that of photosynthesis in plants.
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