cellulose



Cellulose is an organic compound with the formula (C6H10O5)n. It is a structural polysaccharide derived from beta-glucose.[1][2] Cellulose is the primary structural component of green plants. The primary cell wall of green plants is made of cellulose; acetic acid bacteria are also known to synthesize cellulose, as well as many forms of algae, and the oomycetes. Cellulose was discovered and isolated in the mid-nineteenth century by the French chemist Anselme Payen[3][3] and, as of the year 2006, the estimated annual production of 1.5x109 tonnes.[4] Some animals, particularly ruminants and termites, can digest cellulose with the help of symbiotic micro-organisms (see methanogen). Cellulose is not digestible by humans and is often referred to as 'dietary fiber' or 'roughage', acting as a hydrophilic bulking agent for feces.

Commercial products

Cellulose is the major constituent of paper and textiles made from cotton, linen, and other plant fibers. Cellulose can be converted into cellophane, clear rolling papers made from Viscose film, rayon, and more recently cellulose has been used to make Modal, a bio-based textile derived from beechwood cellulose. Cellulose is used within the laboratory as the stationary phase for thin layer chromatography, and cotton linters, is used in the manufacture of nitrocellulose, historically used in smokeless gunpowder.

Rayon is an important fiber made out of cellulose and has been used for textiles since the beginning of the 20th century.

Cellulose source and energy crops

Main article: Energy crop
The major combustible component of non-food energy crops is cellulose, with lignin second. Non-food energy crops are preferred to edible energy crops (which have a large starch component) because they don´t cause inflation of food prices.

Typical non-food energy crops include Switchgrass, Miscanthus, Salix (Willow) and Populus (Poplar) species.

Structure

Cellulose is derived from (β-glucose), which condense through β(1→4)-glycosidic bonds. This linkage motif contrasts with that for α(1→4)-glycosidic bonds present in starch and other carbohydrates. Cellulose is a straight chain polymer: unlike starch, no coiling occurs, and the molecule adopts an extended rod-like conformation. In microfibrils, the multiple hydroxyl groups on the glucose residues hydrogen bond with each other, holding the chains firmly together and contributing to their high tensile strength. This strength is important in cell walls, where they are meshed into a carbohydrate matrix, conferring rigidity to plant cells.

In contrast to starch, cellulose is also much more crystalline. Whereas starch undergoes a crystalline to amorphous transition at 60 -70 °C in water (as in cooking), cellulose requires 320 °C and 25 MPa to become amorphous in water.[5]

Assaying cellulose

Given a cellulose-containing material, the portion that does not dissolve in a 17.5% solution of sodium hydroxide at 20 °C is α cellulose, which is true cellulose. Acidification of the extract precipitates β cellulose. The portion that dissolves in base but does not precipitate with acid is γ cellulose.

Cellulose can be assayed using a method described by Updegraff in 1969, where the fiber is dissolved in acetic and nitric acid, and allowed to react with anthrone in sulfuric acid. The resulting coloured compound is assayed spectrophotometrically at a wavelength of approximately 635 nm.

In addition, cellulose is represented by the difference between acid detergent fiber (ADF) and acid detergent lignin(ADL).

Biosynthesis

In vascular plants cellulose is synthesized at the plasma membrane by rosette terminal complexes (RTC's). The RTC's are hexameric protein structures, approximately 25 nm in diameter that contain the cellulose synthase enzymes that synthesise the individual cellulose chains.[6] The RTC's contain at least three different cellulose synthases, encoded by CesA genes, in an unknown stoichiometry.[7] Separate sets of CesA genes are involved in primary and secondary cell wall biosynthesis. Cellulose synthase utilizes UDP-D-glucose precursors to generate microcrystalline cellulose. Cellulose synthesis requires chain initiation and elongation, and the two processes are separate. CesA glucosyltransferase initiates cellulose polymerization using a steroid primer, 'sitosterol-beta-glucoside' and UDP-glucose.[8] A cellulase may function to cleave the primer from the mature chain.

Breakdown (cellulolysis)

Cellulolysis is the process relating to or causing the hydrolysis of cellulose (i.e. cellulolytic bacteria, fungi or enzymes).

Mammals do not have the ability to break down cellulose directly. Typically, this ability is possessed only by certain bacteria (which have specific enzymes) like Cellulomonas etc., and which are often the flora on the gut walls of ruminants like cows and sheep, or by fungi, which in nature are responsible for cycling of nutrients. The enzymes utilized to the glycosidic linkage in cellulose are glycoside hydrolases including endo-acting cellulases and exo-acting glucosidases. Such enzymes are usually secreted as part of multienzyme complexes that may include dockerins and cellulose binding modules, referred to in some cases as cellulosomes.

Many cellulolytic bacteria, fungi or enzymes break down cellulose into shorter linked chains known as cellodextrins.

Derivatives

The hydroxyl groups of cellulose can be partially or fully reacted with various reagents to afford derivatives with useful properties. Cellulose esters and cellulose ethers are the most important commercial materials. In principle, though not always in current industrial practice, cellulosic polymers are renewable resources.

Among the esters are cellulose acetate and cellulose triacetate, which are film- and fiber-forming materials that find a variety of uses. The inorganic ester nitrocellulose was initially used as an explosive and was an early film forming material.

Ether derivatives include
  • Ethylcellulose, a water-insoluble commercial thermoplastic used in coatings, inks, binders, and controlled-release drug tablets;
  • Methylcellulose;
  • Hydroxypropyl cellulose;
  • Carboxymethyl cellulose;
  • Hydroxypropyl methyl cellulose, E464, used as a viscosity modifier, gelling agent, foaming agent and binding agent;
  • Hydroxyethyl methyl cellulose, used in production of cellulose films.

References

1. ^ Crawford, R. L. (1981). Lignin biodegradation and transformation. New York: John Wiley and Sons. ISBN 0-471-05743-6. 
2. ^ Updegraff DM (1969). "Semimicro determination of cellulose in biological materials". Analytical Biochemistry 32: 420 – 424. 
3. ^ Young, Raymond (1986). Cellulose structure modification and hydrolysis. New York: Wiley. ISBN 0471827614. 
4. ^ Discovery of Cellulose as a Smart Material Jaehwan Kim* and Sungryul Yun Macromolecules, 2006, 4202 -4206, doi:10.1021/ma060261e
5. ^ Cooking cellulose in hot and compressed water Shigeru Deguchi, Kaoru Tsujii and Koki Horikoshi Chem. Commun., 2006, 3293 - 3295, doi:10.1039/b605812d
6. ^ Kimura, Laosinchai, Itoh, Cui, Linder, Brown, Plant Cell, 1999, 11, 2075-2085
7. ^ Taylor, Howells, Huttly, Vickers, Turner, PNAS, 2003,
100, 1450-1455
8. ^ Peng, Kawagoe, Hogan, Delmer, Science, 2002,
295''', 147-150.

See also

External links

organic compounds]] An organic compound is any member of a large class of chemical compounds whose molecules contain carbon; for historical reasons discussed below, a few types of compounds such as carbonates, carbon oxides and cyanides, as well as elemental carbon are
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A chemical formula is a concise way of expressing information about the atoms that constitute a particular chemical compound. A chemical formula is also a short way of showing how a chemical reaction occurs.
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4, 2
(mildly acidic oxide)
Electronegativity 2.55 (Pauling scale)
Ionization energies
(more) 1st: 1086.5 kJmol−1
2nd: 2352.6 kJmol−1
3rd: 4620.5 kJmol−1

Atomic radius 70 pm
Atomic radius (calc.
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1, −1
(amphoteric oxide)
Electronegativity 2.20 (Pauling scale) More

Atomic radius 25 pm
Atomic radius (calc.) 53 pm
Covalent radius 37 pm
Van der Waals radius 120 pm
Miscellaneous

Thermal conductivity (300 K) 180.
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2, −1
(neutral oxide)
Electronegativity 3.44 (Pauling scale)
Ionization energies
(more) 1st: 1313.9 kJmol−1
2nd: 3388.3 kJmol−1
3rd: 5300.5 kJmol−1

Atomic radius 60 pm
Atomic radius (calc.
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Polysaccharides are relatively complex carbohydrates. They are polymers made up of many monosaccharides joined together by glycosidic bonds. They are therefore very large, often branched, macromolecules. They tend to be amorphous, insoluble in water, and have no sweet taste.
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Glucose (Glc), a monosaccharide (or simple sugar), is an important carbohydrate in biology. The living cell uses it as a source of energy and metabolic intermediate.
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Plantae
Haeckel, 1866[1]

Divisions

Green algae
  • Chlorophyta
  • Charophyta
Land plants (embryophytes)
  • Non-vascular land plants (bryophytes)

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Acetobacteraceae

Genera

Acetobacter
Acidicaldus
Acidiphilium
Acidisphaera
Acidocella
Acidomonas
Asaia
Belnapia
Craurococcus
Gluconacetobacter
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phytoplankton — provide the food base for most marine food chains. In very high densities (so-called algal blooms) these algae may discolor the water and outcompete or poison other life forms.
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Oomycetes

Orders

Lagenidiales
Leptomitales
Peronosporales
Rhipidiales
Saprolegniales
Sclerosporales
Water molds (or water moulds: see spelling differences) also known as Oomycetes
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Anselme Payen (January 6, 1795 - May 12, 1871) was a French chemist. He was born in Paris, where his father started to give him scientific lessons at the age of 13. He studied then partly at the École Polytechnique with the best chemists.
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tonne (t) or metric ton (M/T), also referred to as a metric tonne, is a measurement of mass equal to 1,000 kilograms. It is not an SI unit but is accepted for use with the SI.
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Ruminantia

Families

Antilocapridae
Bovidae
Cervidae
Giraffidae
Moschidae
Tragulidae

A ruminant is any animal that digests its food in two steps, first by eating the raw material and regurgitating a semi-digested form known as cud,
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Termites, sometimes known as white ants, are a group of social insects usually classified at the taxonomic rank of order Isoptera. (This has been challenged by recent research, see taxonomy below.
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symbiosis (from the Greek: συμ, sym, "with"; and βίοσίς, biosis, "living") can be used to describe various degrees of close relationship between organisms of different species.
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Methanogens are archaea that produce methane as a metabolic byproduct in anoxic conditions. They are common in wetlands, where they are responsible for marsh gas, and in the guts of animals such as ruminants and humans, where they are responsible for the methane content of
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Digestion is the process of metabolism whereby a biological entity processes a substance in order to chemically and mechanically convert the substance for the body to use.

Overview

Digestion occurs at the multicellular, cellular, and sub-cellular levels, usually in animals.
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Dietary fibers are the indigestible portion of plant foods that move food through the digestive system, absorbing water and making defecation easier. Dietary fiber consists of non-starch polysaccharides such as cellulose and many other plant components such as dextrins, inulin,
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Feces, faeces, or fæces (see spelling differences) is a waste product from an animal's digestive tract expelled through the anus (or cloaca) during defecation. The word faeces is the plural of the Latin word fæx meaning "dregs".
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Paper is thin material used for writing upon, printing upon or packaging, produced by the amalgamation of fibres, typically vegetable fibers composed of cellulose, which are subsequently held together by hydrogen bonding.
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Cellophane is a thin, transparent sheet made of processed cellulose.

Cellulose fibers from wood, cotton or hemp are dissolved in alkali and carbon disulfide to make a solution called viscose, which is then extruded through a slit into an acid bath to reconvert the viscose
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Viscose is a viscous organic liquid used to make rayon and cellophane. Cellulose from wood or cotton fibres is treated with sodium hydroxide, then mixed with carbon disulfide to form cellulose xanthate, which is dissolved in more sodium hydroxide.
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For the subnational entity, see Raion.
Rayon is a manufactured regenerated cellulosic fiber. Rayon is produced from naturally occurring polymers and therefore it is not a truly synthetic fiber, nor is it a natural fiber.
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Modal is a bio-based fiber made by spinning reconstituted cellulose from beech trees. It is about 50% more hygroscopic, or water-absorbent, per unit volume than cotton is. It is designed to dye just like cotton, and is color-fast when washed in warm water.
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A bio-based material is simply an engineering material made from substances derived from living matter. These materials are sometimes referred to as biomaterials, but this word also has another meaning.
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Chromatography (from Greek χρώμα:chroma, colour and γραφειν:"grafein" to write) is the collective term for a family of laboratory techniques for the separation of mixtures.
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Cotton is a soft fibre that grows around the seeds of the cotton plant (Gossypium sp.), a shrub native to tropical and subtropical regions around the world, including the Americas, India, and Africa.
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Nitrocellulose (also: cellulose nitrate, flash paper) is a highly flammable compound formed by nitrating cellulose through, for example, exposure to nitric acid or another powerful nitrating agent.
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