cellulose

Examples of cellulose in the following topics:

• Polysaccharides

  • Cotton fibers are essentially pure cellulose, and the wood of bushes and trees is about 50% cellulose.
  • The structure of starch is more complex than that of cellulose.
  • These less desirable cellulose sources are widely used for making paper.
  • Cellulose Nitrate, first prepared over 150 years ago by treating cellulose with nitric acid, is the earliest synthetic polymer to see general use.
  • Partially nitrated cellulose is called pyroxylin.

• Genomics and Biofuels

  • These include Clostridia species for their ability to degrade cellulose, and fungi that express genes associated with the decomposition of the most recalcitrant features of the plant cell wall, lignin, the phenolic "glue" that imbues the plant with structural integrity and pest resistance.
  • The white rot fungus Phanerochaete chrysosporium produces unique extracellular oxidative enzymes that effectively degrade lignin by gaining access through the protective matrix surrounding the cellulose microfibrils of plant cell walls.
  • Pathway engineering promises to produce a wider variety of organisms able to ferment the full repertoire of sugars derived from cellulose and hemicellulose and tolerate higher ethanol concentrations to optimize fuel yields.
  • For instance, the hindgut contents of nature's own bioreactor, the termite, has yielded more than 500 genes related to the enzymatic deconstruction of cellulose and hemicellulose .
  • The hindgut of the termite has yielded more than 500 genes of microbes related to the enzymatic deconstruction of cellulose.

• The Rumen and Ruminant Animals

  • Specialized microbe species live in the rumen and help ruminants break down cellulose.
  • The plant matter consumed by ruminants is high in cellulose, but vertebrates cannot produce cellulase which is the enzyme required to break down cellulose.
  • Thus ruminants depend on the symbiotic microbes in their guts to break down cellulose for digestion.

• Carbohydrate Molecules

  • Starch, glycogen, cellulose, and chitin are primary examples of polysaccharides.
  • Cellulose is the most abundant natural biopolymer.
  • The cell wall of plants is mostly made of cellulose and provides structural support to the cell.
  • Cellulose is made up of glucose monomers that are linked by β 1-4 glycosidic bonds .
  • In cellulose, glucose monomers are linked in unbranched chains by β 1-4 glycosidic linkages.

• Properties of Macromolecules

  • A comparison of the properties of polyethylene (both LDPE & HDPE) with the natural polymers rubber and cellulose is instructive.
  • Cellulose fibers may be bent and twisted, but do not stretch much before breaking.
  • The monomer of cellulose is the C6H12O6 aldohexose D-glucose.
  • To begin with, cellulose chains easily adopt a stable rod-like conformation.
  • Note that cellulose has neither a Tm nor a Tg.

• Biodegradable Polymers

  • Plastics derived from natural materials, such as cellulose, starch and hydroxycarboxylic acids are more easily decomposed when exposed to oxygen, water, soil organisms and sunlight than are most petroleum based polymers.
  • Derivatives of cellulose, such as cellulose acetate, have long served for the manufacture of films and fibers.
  • The most useful acetate material is the diacetate, in which two thirds of the cellulose hydroxyl groups have been esterified.
  • The other major polysaccharide, starch, is less robust than cellulose, but in pelletized form it is now replacing polystyrene as a packing material.

• Herbivores, Omnivores, and Carnivores

  • Since some parts of plant materials, such as cellulose, are hard to digest, the digestive tract of herbivores is adapted so that food may be digested properly.
  • Many large herbivores have symbiotic bacteria within their guts to assist with the breakdown of cellulose.
  • Some herbivores contain symbiotic bacteria within their intestines to aid with the digestion of the cellulose found in plant cell walls.

• Vertebrate Digestive Systems

  • They have evolved digestive systems that help them process vast amounts of cellulose.
  • These chambers contain many microbes that break down cellulose and ferment ingested food.
  • Digesting plant material is not easy because plant cell walls contain the polymeric sugar molecule cellulose.
  • The digestive enzymes of these animals cannot break down cellulose, but microorganisms present in the digestive system can.
  • The first two stomachs, the rumen and the reticulum, contain prokaryotes and protists that are able to digest cellulose fiber.

• Syntrophy and Methanogenesis

  • The protozoans break down the cellulose consumed by termites, and release hydrogen, which is then used in methanogenesis .
  • The protozoans break down cellulose, releasing H2 which is then used in methanogenesis.

• Cooperation Among Microorganisms

  • These animals eat cellulose which is broken down by the protozoa to obtain energy.
  • The protozoans break down cellulose, releasing H2 which is then used in methanogenesis.