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Amylose is a polysaccharide made of α-D-glucose units, bonded to each other through α(1→4) glycosidic bonds. It is one of the two components of starch , making up approximately 20–25% of it. Because of its tightly packed helical structure, amylose is more resistant to digestion than other starch molecules and is therefore an important ...
3D structure of cellulose, a beta-glucan polysaccharide Amylose is a linear polymer of glucose mainly linked with α(1→4) bonds. It can be made of several thousands of glucose units. It is one of the two components of starch, the other being amylopectin.
It consists of two types of molecules: the linear and helical amylose and the branched amylopectin. Depending on the plant, starch generally contains 20 to 25% amylose and 75 to 80% amylopectin by weight. [4] Glycogen, the energy reserve of animals, is a more highly branched version of amylopectin.
For example, milk sugar (lactose) is a disaccharide made by condensation of one molecule of each of the monosaccharides glucose and galactose, whereas the disaccharide sucrose in sugar cane and sugar beet, is a condensation product of glucose and fructose. Maltose, another common disaccharide, is condensed from two glucose molecules. [7]
The ratio between these is usually between 0.8 to 1.4. [9] [10] Cluster model of amylopectin. The formation of chain structures has a direct impact on the overall strength of the polymeric whole; the longer a chain is, the more differing the effects amylopectin will have on starch’s morphology.
The straight shape allows the molecules to pack closely. Cellulose is very common in application due to its abundant supply, its biocompatibility, and is environmentally friendly. Cellulose is used vastly in the form of nano-fibrils called nano-cellulose. Nano-cellulose presented at low concentrations produces a transparent gel material.
In contrast to cellulose, hemicelluloses are derived from several sugars in addition to glucose, especially xylose but also including mannose, galactose, rhamnose, and arabinose. Hemicelluloses consist of shorter chains – between 500 and 3000 sugar units. [48] Furthermore, hemicelluloses are branched, whereas cellulose is unbranched.
A reducing sugar is one that reduces another compound and is itself oxidized; that is, the carbonyl carbon of the sugar is oxidized to a carboxyl group. [2] A sugar is classified as a reducing sugar only if it has an open-chain form with an aldehyde group or a free hemiacetal group. [3]