Polysaccharides

(noun)

Polysaccharides are long, carbohydrate molecules of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit.

Related Terms

Examples of Polysaccharides in the following topics:

  • Polysaccharide Biosynthesis

    • Polysaccharides are synthesized from two forms of activated glucose molecules: UDP-glucose and ADP-glucose.
    • Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit.
    • One of the most common building block of polysaccharides is glucose.
    • Pathogenic bacteria commonly produce a thick, mucous-like, layer of polysaccharide.
    • Describe the mechanism of polysaccharide biosynthesis and its importance in bacteria

  • Carbohydrate Molecules

    • Carbohydrates are essential macromolecules that are classified into three subtypes: monosaccharides, disaccharides, and polysaccharides.
    • Carbohydrates are classified into three subtypes: monosaccharides, disaccharides, and polysaccharides.
    • A long chain of monosaccharides linked by glycosidic bonds is known as a polysaccharide (poly- = "many").
    • Starch, glycogen, cellulose, and chitin are primary examples of polysaccharides.
    • This exoskeleton is made of chitin, which is a polysaccharide-containing nitrogen.

  • Glycocalyx

    • A glycocalyx(capsule or slime layer)is an external coating of bacteria with protective function, made mostly of polysaccharides.
    • A glycocalyx, literally meaning "sugar coat", is a network of polysaccharides that project from cellular surfaces of bacteria, which classifies it as a universal surface component of a bacterial cell, found just outside the bacterium cell wall.
    • It usually consists of polysaccharides, but can be composed of other materials (e.g., polypeptide in B. anthracis).

  • Polysaccharides

    • As the name implies, polysaccharides are large high-molecular weight molecules constructed by joining monosaccharide units together by glycosidic bonds.
    • Partial hydrolysis of starch and glycogen produces the disaccharide maltose together with low molecular weight dextrans, polysaccharides in which glucose molecules are joined by alpha-glycoside links between C-1 and C-6, as well as the alpha C-1 to C-4 links found in maltose.
    • Polysaccharides built from other monosaccharides (e.g. mannose, galactose, xylose and arabinose) are also known, but will not be discussed here.
    • The degree of branching in these polysaccharides may be measured by enzymatic or chemical analysis.
    • Many complex polysaccharides are found in nature.

  • ABC Transporters

    • In gram-negative bacteria, exporters transport lipids and some polysaccharides from the cytoplasm to the periplasm.
    • In bacterial efflux systems, certain substances that need to be extruded from the cell include surface components of the bacterial cell (e.g. capsular polysaccharides, lipopolysaccharides, and teichoic acid), proteins involved in bacterial pathogenesis (e.g. hemolysis, heme-binding protein, and alkaline protease), heme, hydrolytic enzymes, S-layer proteins, competence factors, toxins, antibiotics, bacteriocins, peptide antibiotics, drugs and siderophores.
    • They also play important roles in biosynthetic pathways, including extracellular polysaccharide biosynthesis and cytochrome biogenesis.

  • Bacterial Flora

    • For example, undigested polysaccharides (fiber) are metabolized to short-chain fatty acids by bacteria in the large intestine and then absorbed by passive diffusion.
    • These are produced as a result of bacterial fermentation of undigested polysaccharides.

  • Biosynthesis and Energy

    • An additional biosynthetic pathway utilized by microorganisms includes the synthesis of sugars and polysaccharides.
    • The ability to synthesize sugars and polysaccharides from noncarbohydrate precursors is key to survival in numerous microorganisms.

  • Dehydration Synthesis

    • These three are polysaccharides, classified as carbohydrates, that have formed as a result of multiple dehydration synthesis reactions between glucose monomers.
    • However, the manner by which glucose monomers join together, specifically locations of the covalent bonds between connected monomers and the orientation (stereochemistry) of the covalent bonds, results in these three different polysaccharides with varying properties and functions.

  • Absorption and Feces Formation in the Large Intestine

    • Undigested polysaccharides (fiber) are metabolized to short-chain fatty acids by bacteria in the large intestine and absorbed by passive diffusion.
    • Bacterial fermentation of undigested polysaccharides produces these gases.

  • Metabolism of Carbohydrates

    • Plants store carbohydrates in long polysaccharides chains called starch, while animals store carbohydrates as the molecule glycogen.
    • These large polysaccharides contain many chemical bonds and therefore store a lot of chemical energy.