Biomedical Engineering Reference
In-Depth Information
HO
HO
5
5
O
O
4
1
4
1
2
3
2
3
OH
OH
OH
OH
OH
D -ribose
Deoxyribose
2.3.2.2. Disaccharides
Disaccharides are formed by the condensation of two monosaccharides. For example,
sucrose is formed by the condensation of one ( a - D -) glucose molecule and one ( b - D -) fructose
molecule via a -l,4 glycosidic linkage (or a -1-O-4). This can be illustrated as follows:
HO
HO
HO
HO
1
5
O
O
O
O
OH
OH
HO
4
1
HO
2
HO
5
+
H 2 O
2
+
3
O
3
4
HO
HO
OH
6
OH
OH
OH
OH
OH
OH
α
- D -glucose
β
- D -fructose
Sucrose
2- b - D -fructofuranose.
Maltose is a disaccharide of two identical a - D -glucose molecules. Lactose is a disaccharide
of b - D -glucose and b - D -galactose. The stereo structures of these two disaccharides are shown
below:
Sucrose can also be represented as a - D -glucopyranose-1
/
HO
HO
HO
OH
O
O
O
O
OH
OH
OH
OH
O
O
HO
HO
OH
OH
OH
OH
OH
OH
α
- D -glucopyranose-1
4-
α
- D -glucopyranose
β
- D -glucopyranose-1
4-
β
- D -galactopyranose
Maltose
Lactose
Lactose is found in milk and whey, while sucrose is the major sugar in photosynthetic
plants. Whey utilization remains an important biotechnological challenge; sucrose is often
a major component in artificial growth media.
2.3.2.3. Polysaccharides
Polysaccharides are formed by the condensation of two or more monosaccharides by glyco-
sidic bonds. The polysaccharide processing industry makes extensive use of enzymatic pro-
cessing and biochemical engineering.
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