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Polysaccharides are relatively complex "unsweet" carbohydrates. Polysaccharides are polymers made up of many monosaccharides joined together (hence poly-saccharides). They are therefore very large, often branched, molecules. Properties include insolubility in water and not forming crystals. Examples include starch, cellulose, and glycogen.Structure
Polysaccharides have the general formula:
- -[Cx(H2O)y)]n-
where y is generally = x - 1.
1 Starches
Starches are polymers of glucose in which glucopyranose units are bonded by alpha-linkages. Amylose consists of a linear chain of several hundred of glucose molecules. Amylopectine is a branched molecule made of several thousand of glucose units.
Starches are insoluble in water. They can be digested by hydrolysis catalyzed by enzymes called amylases, which can break the alpha-linkages. Humans and other animals have amylases, so they can digest starches. Potato, rice, wheat, and maize are major sources of starch in the human diet.
2 Glycogen
Glycogen is the storage form of glucose in animals. It is a branched polymer of glucose. Glycogen can be broken down to form substrates for respiration, through the process of glycogenolysisGlycogenolysis is the catabolism of glycogen (requiring removal of glucose unit from glycogen and addition of phosphate) thus producing glucose-1-phosphate. Glycogenolysis requires three enzymes : Phosphorylase Glucan Transferase Debranching enzyme.. This involves the breaking of most of the C-O-C bonds between the glucose molecules by the addition of a phosphate, rather than a water as in hydrolysisHydrolysis is a chemical process in which a molecule is cleaved into two parts by the addition of a molecule of water. This is distinct from a hydration reaction, in which water molecules are added to a substance, but no cleavage occurs. Types Hydrolysis. This process yields phosphorylated glucose molecules, which can be metabolized with a savings of one ATPFor other uses of the initials ATP, see ATP (disambiguation Adenosine triphosphate ATP is the nucleotide known in biochemistry as the " molecular currency" of intracellular energy transfer; that is, ATP is able to store and transport chemical energy withi molecule.
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3 Cellulose
The structural components of plantGreen algae land plants (embryophytes non-vascular embryophytes Hepatophyta liverworts Anthocerophyta hornworts Bryophyta mosses vascular plants (tracheophytes seedless vascular plants Lycopodiophyta clubmosses Equisetophyta horsetails Pteridophyta "true"s are formed primarily from cellulose. Wood is largely cellulose and ligninLignin is a chemical compound that is an integral part of the cell walls of some cells, eg tracheids, xylary fibres and sclereids of plants. Lignin is formed by the irreversible removal of water from sugars, creating aromatic compounds through the phenylp, while paperPaper is a thin, flat material produced by the compression of fibres. The fibers used are usually natural and based upon cellulose. The most common material is wood pulp from pulpwood (largely softwood) trees such as pines, but other vegetable fiber mater and cotton are nearly pure cellulose. Cellulose is a polymer made with repeated glucose units bonded together by beta-linkages. Humans and many other animals lack an enzyme to break the beta-linkages, so they do not digest cellulose. Certain animals can digest cellulose, because the enzyme is present.
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