72
1
General Principles
charides impart some form of early immunological protection to the newborn. See > Fig. 5
for the structure of lactose.
4.2.4 Properties and Occurrence of α-D-Glucose
Combined with α-D-Glucose to Give α,α-Trehalose
α,α-Trehalose is also one of the three naturally occurring disaccharides. It is a nonreducing
disaccharide with two D-glucopyranose residues joined together in an α-1↔α-1 acetal–acetal
linkage and is of relatively high energy, like sucrose. Unlike sucrose, however, the acetal–
acetal linkage is quite stable and is one of the most difficult linkages to be hydrolyzed by
acid. The reason for this is not absolutely clear, but it has been hypothesized to be due to
the stabilization of the molecule by intramolecular hydrogen bonds between the D-glucose
residues. α,α-Trehalose is found in insect lymph fluid (“insect blood”) where it acts as a source
of chemical energy [19] and it is also found in mushrooms, honey, yeast, fungi, lobster, and
shrimp as a source of energy [20,21] all of which have the enzyme, trehalase, that hydrolyzes
α,α-trehalose to give two molecules of D-glucose that can be used for energy.
Besides being used as a source of energy, some plants and animals also use α,α-trehalose as
a stabilizing agent during extreme conditions [22]. High concentrations of α,α-trehalose in the
tissues of certain insects and in desert plants allows them to survive in a state of suspended animation under conditions of water deficiency. α,α-Trehalose helps frogs to survive in a frozen
state and it helps to protect the DNA of salmon sperm from dehydration. α,α-Trehalose has
also found applications in the preservation of organs taken for use in organ transplants [23,24].
See > Fig. 5 for the structure of α,α-trehalose.
5 Properties and Occurrence of D-Glucose
in Polysaccharides and Cyclodextrins
5.1 Properties and Occurrence of Starch
Starch is an abundant polysaccharide composed of D-glucose residues. It is found in the green
leaves, stems, roots, seeds, fruits, tubers, and bulbs of most plants, where it serves as the storage
of chemical energy obtained from the energy of the sun light in the process of photosynthesis.
Starch also serves as the major source of chemical energy for most nonphotosynthesizing
organisms such as bacteria, fungi, insects, and animals. It is found in relatively large amounts
in the major food crops of the world. Starch is present 80% by weight in the rice kernel, 78%
in the potato tuber, 75% in green bananas, 73% in the maize kernel, 68% in wheat flour, and
60% in rye and lentils. Starch provides about 65% of the dietary calories in the human diet.
Starch occurs in plants as water-insoluble granules produced in plant organelles, plastids
(chloroplasts and amyloplasts). The granules have specific shapes and sizes that are characteristic of their botanical source [25]. Most starches are composed of a mixture of two types
of polysaccharides, a linear polysaccharide, consisting of α-(1→4) linked D-glucopyranose
residues, called amylose, and a branched polysaccharide of α-(1→4) linked D-glucopyranose
1
General Principles
charides impart some form of early immunological protection to the newborn. See > Fig. 5
for the structure of lactose.
4.2.4 Properties and Occurrence of α-D-Glucose
Combined with α-D-Glucose to Give α,α-Trehalose
α,α-Trehalose is also one of the three naturally occurring disaccharides. It is a nonreducing
disaccharide with two D-glucopyranose residues joined together in an α-1↔α-1 acetal–acetal
linkage and is of relatively high energy, like sucrose. Unlike sucrose, however, the acetal–
acetal linkage is quite stable and is one of the most difficult linkages to be hydrolyzed by
acid. The reason for this is not absolutely clear, but it has been hypothesized to be due to
the stabilization of the molecule by intramolecular hydrogen bonds between the D-glucose
residues. α,α-Trehalose is found in insect lymph fluid (“insect blood”) where it acts as a source
of chemical energy [19] and it is also found in mushrooms, honey, yeast, fungi, lobster, and
shrimp as a source of energy [20,21] all of which have the enzyme, trehalase, that hydrolyzes
α,α-trehalose to give two molecules of D-glucose that can be used for energy.
Besides being used as a source of energy, some plants and animals also use α,α-trehalose as
a stabilizing agent during extreme conditions [22]. High concentrations of α,α-trehalose in the
tissues of certain insects and in desert plants allows them to survive in a state of suspended animation under conditions of water deficiency. α,α-Trehalose helps frogs to survive in a frozen
state and it helps to protect the DNA of salmon sperm from dehydration. α,α-Trehalose has
also found applications in the preservation of organs taken for use in organ transplants [23,24].
See > Fig. 5 for the structure of α,α-trehalose.
5 Properties and Occurrence of D-Glucose
in Polysaccharides and Cyclodextrins
5.1 Properties and Occurrence of Starch
Starch is an abundant polysaccharide composed of D-glucose residues. It is found in the green
leaves, stems, roots, seeds, fruits, tubers, and bulbs of most plants, where it serves as the storage
of chemical energy obtained from the energy of the sun light in the process of photosynthesis.
Starch also serves as the major source of chemical energy for most nonphotosynthesizing
organisms such as bacteria, fungi, insects, and animals. It is found in relatively large amounts
in the major food crops of the world. Starch is present 80% by weight in the rice kernel, 78%
in the potato tuber, 75% in green bananas, 73% in the maize kernel, 68% in wheat flour, and
60% in rye and lentils. Starch provides about 65% of the dietary calories in the human diet.
Starch occurs in plants as water-insoluble granules produced in plant organelles, plastids
(chloroplasts and amyloplasts). The granules have specific shapes and sizes that are characteristic of their botanical source [25]. Most starches are composed of a mixture of two types
of polysaccharides, a linear polysaccharide, consisting of α-(1→4) linked D-glucopyranose
residues, called amylose, and a branched polysaccharide of α-(1→4) linked D-glucopyranose