The amylopectin is a highly branched carbohydrate and it is water-soluble. Its solubility is due to the many end points at which the enzymes can attach. This makes amylopectin different from amylose. The amylose is relatively not as soluble. Thus, compared with amylose, amylopectin can be hydrolyzed more readily, more soluble, and with lower density.
In animals, the amylopectin is similar in composition and structure. It occurs in glycogen which is regarded by others as the animal starch.
Similar to starch, the glycogen is a complex carbohydrate that stores excess glucose. Heteropolymers are common in nature gums, pectins, and other substances but will not be discussed further in this textbook.
The polysaccharides are nonreducing carbohydrates, are not sweet tasting, and do not undergo mutarotation. It occurs in plants in the form of granules, and these are particularly abundant in seeds especially the cereal grains and tubers, where they serve as a storage form of carbohydrates. The breakdown of starch to glucose nourishes the plant during periods of reduced photosynthetic activity.
Commercial starch is a white powder. Starch is a mixture of two polymers: amylose and amylopectin. When coiled in this fashion, amylose has just enough room in its core to accommodate an iodine molecule. The characteristic blue-violet color that appears when starch is treated with iodine is due to the formation of the amylose-iodine complex. This color test is sensitive enough to detect even minute amounts of starch in solution.
The helical structure of amylopectin is disrupted by the branching of the chain, so instead of the deep blue-violet color amylose gives with iodine, amylopectin produces a less intense reddish brown. Dextrins are glucose polysaccharides of intermediate size. The shine and stiffness imparted to clothing by starch are due to the presence of dextrins formed when clothing is ironed.
Because of their characteristic stickiness with wetting, dextrins are used as adhesives on stamps, envelopes, and labels; as binders to hold pills and tablets together; and as pastes.
Dextrins are more easily digested than starch and are therefore used extensively in the commercial preparation of infant foods. In the human body, several enzymes known collectively as amylases degrade starch sequentially into usable glucose units. Glycogen is the energy reserve carbohydrate of animals. Skip to content Main Navigation Search. Dictionary Articles Tutorials Biology Forum. Adaptation Tutorial Adaptation, in biology and ecology, refers to the process or trait through which organisms or the populations in a habit..
Origins of Life on Earth Earth was created around 4. Human Biology — Food and Digestion This tutorial recognizes the importance of food as a source of energy that will fuel many biological processes. Genetic Information and Protein Synthesis Genes are expressed through the process of protein synthesis.
Animal Water Regulation Animals adapt to their environment in aspects of anatomy, physiology, and behavior. Passive and Active Types of Immunity Lymphocytes are a type of white blood cell capable of producing a specific immune response to unique antigens. This step ultimately yields glucose monomers that are then transported into the small intestinal enterocyte by co-transport with sodium ions. Several definitions have been proposed for "fiber". An early definition, still quite appropriate, basically states that fiber is the portion of food derived from plant cell walls that is poorly digested by mammals.
Another common definition for fiber is the non-starch polysaccharide component of foodstuffs. The chief components of dietary fiber are cellulose and hemicellulose, both of plant origin. Pectin and pectic acid are other plant polysaccharides often present in diets. Cellulose is a linear polymer of between and 10, beta-D-glucose molecules in which adjacent glucose molecules are joined covalently through beta glycosidic bonds.
The beta bonds cause the polymer to assume a non-helical, straight structure, which is different from the helical structure imposed on starch molecules by the alpha bonding. The non-helical structure of cellulose also promotes hydrogen bonding between cellulose molecules.
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