General Properties, Occurrence, and Preparation
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age and form such carbohydrate substances as, starch, dextran, cellulose, sucrose, lactose,
α,α-trehalose.
4.2.1 Occurrence of D-Glucose Combined with D-Fructose, D-Galactose,
and D-Glucose, and High-Energy D-Glucose Donors
There are three major, naturally occurring disaccharides: sucrose, lactose, and α,α-trehalose
and D-glucopyranose is found in all three. Sucrose is a nonreducing disaccharide composed of D-glucopyranose joined to D-fructofuranose (1→2) to give α-D-glucopyranosyl(1→2)-β-D-fructofuranoside. Sucrose is widely distributed in plants, primarily as 6 Fru -
phosphosucrose, which is the transport form of carbohydrates in plants. When it reaches
certain parts of the plant, the glucose moiety is converted into starch by a series of reactions
that give adenosine-diphospho-glucose (ADPGlc) or uridine-diphospho-glucose (UDPGlc),
high-energy donors of glucose for the biosynthesis of starch and cellulose, respectively. Relatively large amounts (15–20% by weight) of free sucrose are found in the stems and tubers
of sugar cane and the tubers of sugar beets. Free sucrose is also found in many other plants
but in lower amounts, such as their fruits. Sucrose is the predominant sugar found in honey,
produced by bees, in the sap of maple trees, giving maple syrup, and in sorghum, and in dates.
See > Fig. 5 for the structures of sucrose, lactose, and α,α-trehalose and > Fig. 4 for the
structures of ADPGlc and UDPGlc.
4.2.2 Properties and Occurrence of Sucrose
and Sucrose Oligosaccharides Containing D-Galactose
Sucrose has five important properties: (a) the linkage between D-glucopyranose and D-fructofuranose is of high energy being an acetal–ketal linkage of a six-membered ring attached to
a five-membered ring, making sucrose a nonreducing sugar. (b) The acetal–ketal linkage is
⊡ Figure 5
Structures of the three naturally occurring disaccharides: sucrose, lactose, and α-α-trehalose, containing α-Dglucopyranose combined with β-D-fructofuranose, β-D-galactopyranose, and α-D-glucopyranose, respectively
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69
age and form such carbohydrate substances as, starch, dextran, cellulose, sucrose, lactose,
α,α-trehalose.
4.2.1 Occurrence of D-Glucose Combined with D-Fructose, D-Galactose,
and D-Glucose, and High-Energy D-Glucose Donors
There are three major, naturally occurring disaccharides: sucrose, lactose, and α,α-trehalose
and D-glucopyranose is found in all three. Sucrose is a nonreducing disaccharide composed of D-glucopyranose joined to D-fructofuranose (1→2) to give α-D-glucopyranosyl(1→2)-β-D-fructofuranoside. Sucrose is widely distributed in plants, primarily as 6 Fru -
phosphosucrose, which is the transport form of carbohydrates in plants. When it reaches
certain parts of the plant, the glucose moiety is converted into starch by a series of reactions
that give adenosine-diphospho-glucose (ADPGlc) or uridine-diphospho-glucose (UDPGlc),
high-energy donors of glucose for the biosynthesis of starch and cellulose, respectively. Relatively large amounts (15–20% by weight) of free sucrose are found in the stems and tubers
of sugar cane and the tubers of sugar beets. Free sucrose is also found in many other plants
but in lower amounts, such as their fruits. Sucrose is the predominant sugar found in honey,
produced by bees, in the sap of maple trees, giving maple syrup, and in sorghum, and in dates.
See > Fig. 5 for the structures of sucrose, lactose, and α,α-trehalose and > Fig. 4 for the
structures of ADPGlc and UDPGlc.
4.2.2 Properties and Occurrence of Sucrose
and Sucrose Oligosaccharides Containing D-Galactose
Sucrose has five important properties: (a) the linkage between D-glucopyranose and D-fructofuranose is of high energy being an acetal–ketal linkage of a six-membered ring attached to
a five-membered ring, making sucrose a nonreducing sugar. (b) The acetal–ketal linkage is
⊡ Figure 5
Structures of the three naturally occurring disaccharides: sucrose, lactose, and α-α-trehalose, containing α-Dglucopyranose combined with β-D-fructofuranose, β-D-galactopyranose, and α-D-glucopyranose, respectively