Polysaccharides amylose and amylopectin

Starch, in foods like potatoes, contains the polysaccharides amylose and amylopectin. Like cellnlose, amylose, is a linear polymer of D-glucose. However, the linkages are now 1,4-a instead of 1,4-, as illustrated schematically in Figure 9-36. This seemingly minor change results in a significant difference in properties, however. Amylose is a much more flexible molecule than cellulose and can form a regular helix with six residues per turn. 

Starch, a food-reserve substance from plant grains, is a mixture of two polysaccharides, amylose and amylopectin (Kennedy and White 1988). Amylose is... 

Starch is a polysaccharide composed exclusively of D-glucose and is one of the three most abundant organic compounds found on Earth (cellulose and murein being the other two abundant compounds). Most starches are composed of two types of polysaccharides amylose and amylopectin. The former is a mixture of linear polysaccharides of D-glucose units linked a-1 4 to each other. The latter consists of a mixture of branched polysaccharides of D-glucose unit linked a-1 4, with 5% of a-1 6 branch linkages corre-... 

The major kinds of digestible carbohydrates in foods are the simple sugars (glucose and fructose), disaccharides (sucrose, maltose, and lactose), and polysaccharides (amylose and amylopectin in starch from plants, and glycogen from meat). The indigestible carbohydrates include cellulose and its derivatives, pectin (the substance that makes jam and jelly gel), and plant gums. 

Cellulose not only provides the support substance of wood, but also that for all other plants. Flax stalk husks provide linen and hemp is obtained from the leaves of the sisal plant. Cotton fibers are recovered from the seed hairs of the cotton bush. What are known as vegetable gums, which are also polysaccharides, are to be found in other seeds and algae. Starch is recovered from grain seeds, and starch is a mixture of the polysaccharides amylose and amylopectin. Pectin, an acidic polysaccharide, is provided by fruits. Latices containing the polyprenes natural rubber, balata, gutta percha, or chicle are obtained from certain trees and plants. 

Starch is found in all plant seeds and tubers and is the form in which glucose is stored for later use. Starch can be separated into two principal polysaccharides amylose and amylopectin. Although the starch from each plant is unique, most starches contain 20 to 25% amylose and 75 to 80% amylopectin. 

Starch can be separated into two principal polysaccharides amylose and amylopectin. What is the major difference in structure between the two ... 

Starches differ in their chemical composition and, except in rare instances, are mixtures of two structurally different polysaccharides, amylose and amylopectin. The proportions of these present in natural starches depend upon the source, although in most starches amylopectin is the main component, amounting to about 70-80 per cent of the total. An important qualitative test for starch is its reaction with iodine amylose produces a deep blue colour and amylopectin solutions produce a blue-violet or purple colour. 

Starch, a storage form of glucose in plants, is found as insoluble granules in rice, wheat, potatoes, beans, and cereals. Starch is composed of two kinds of polysaccharides, amylose and amylopectin. Amylose, which makes up about 20% of starch, consists of a-glucose molecules connected by a-l,4-glycosidic bonds in a continuous chain. A typical polymer of amylose may contain from 250 to 4000 a-o-glucose molecules. Sometimes called a sttaight-chain polymer, polymers of amylose are actually coiled in hehcal fashion. 

Energy-Storage Polysaccharides. Among the energy reserve polysaccharides one must recall that in nature starch is distributed almost as widely as cellulose. It is a mixture of two polysaccharides, amylose and amylopectin, both of which have covalent structures based on chains of 1,4-linked-a -D-glucopyranose units (Fig. 1.6). 

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