Cellulose 6911 224929921 2008-07-11T01:32:56Z 220.233.126.215 rv probable vandalism existing since edit by 129.11.13.133 on 18th May [[Image:Cellulose-2D-skeletal.svg|thumb|right|260px|Cellulose, a linear polymer of <small>D</small>-[[glucose]] linked by β(1→4)-[[glycosidic bond]]s.]] [[Image:Cellulose-3D-balls.png|thumb|right|260px|Three-dimensional structure of cellulose, with four glucose units visible. (Black=carbon; red=oxygen; white=hydrogen.)]] [[Image:Cellulose-3D-vdW.png|thumb|right|260px|Space-filling model of cellulose, with four glucose units visible]] '''Cellulose''' is an [[organic compound]] with the [[chemical formula|formula]] {{chem|([[carbon|C]]|6|[[hydrogen|H]]|10|[[oxygen|O]]|5|)|n}}, a [[polysaccharide]] consisting of a linear chain of several hundred to over ten thousand β(1→4) linked <small>D</small>-[[glucose]] units.<ref name=Crawford>{{cite book | author=Crawford, R. L. | title=Lignin biodegradation and transformation | publisher=John Wiley and Sons | location = New York | year=1981 | id=ISBN 0-471-05743-6 }}</ref><ref>{{cite journal | author=Updegraff DM | title=Semimicro determination of cellulose in biological materials | journal=Analytical Biochemistry | year=1969 | volume=32 | pages=420 – 424 | doi=10.1016/S0003-2697(69)80009-6 }}</ref> Cellulose is the structural component of the primary [[cell wall]] of [[green plants]], many forms of [[algae]] and the [[oomycetes]]. Some species of [[bacteria]] secrete it to form [[biofilm]]s. Cellulose is the most common organic compound on Earth. About 33 percent of all plant matter is cellulose (the cellulose content of [[cotton]] is 90 percent and that of wood is 50 percent).<ref>Cellulose. (2008). In ''[[Encyclopædia Britannica]]''. Retrieved January 11, 2008, from Encyclopædia Britannica Online.</ref> For industrial use, cellulose is mainly obtained from [[wood pulp]] and [[cotton]]. It is mainly used to produce [[cardboard]] and [[paper]]; to a smaller extent it is converted into a wide variety of derivative products such as [[cellophane]] and [[rayon]]. Some animals, particularly [[ruminant]]s and [[termite]]s, can [[digestion|digest]] cellulose with the help of [[symbiosis|symbiotic]] micro-organisms that live in their guts. Cellulose is not digestible by [[human]]s and is often referred to as '[[dietary fiber]]' or 'roughage', acting as a [[hydrophilic]] bulking agent for [[feces]]. ==History== Cellulose was discovered in 1838 by the French chemist [[Anselme Payen]], who isolated it from plant matter and determined its chemical formula.<ref name=Crawford /><ref name="Young">{{cite book | last = Young | first = Raymond | title = Cellulose structure modification and hydrolysis | publisher = Wiley | location = New York | year = 1986 | isbn = 0471827614 }}</ref> Cellulose was used to produce the first successful [[thermoplastic|thermoplastic polymer]], [[celluloid]], by Hyatt Manufacturing Company in 1870. [[Hermann Staudinger]] determined the polymer structure of cellulose in 1920. The compound was first chemically synthesized (without the use of any biologically-derived [[enzyme]]s) in 1992, by Kobayashi and Shoda.<ref name=Klemm>{{Cite journal | volume = 36 | issue = 36 | last = Klemm | first = Dieter | coauthors = Brigitte Heublein, Hans-Peter Fink, Andreas Bohn | title = Cellulose: Fascinating Biopolymer and Sustainable Raw Material | journal = ChemInform | date = 2005 | doi = 10.1002/chin.200536238 <!--Retrieved from url by DOI bot--> }}</ref> ==Commercial products== Cellulose is the major constituent of paper and cardboard and of textiles made from [[cotton]], [[linen]], and other plant fibers. Cellulose can be converted into [[cellophane]], a thin transparent film, and into [[rayon]], an important fiber that has been used for textiles since the beginning of the 20th century. Both cellophane and rayon are known as "regenerated cellulose fibers"; they are identical to cellulose in chemical structure and are usually made from [[viscose]], a [[viscous]] solution made from cellulose. A more recent and environmentally friendly method to produce rayon is the [[Lyocell]] process. Cellulose is used in the laboratory as the stationary phase for [[Chromatography|thin layer chromatography]]. It is the raw material in the manufacture of [[nitrocellulose]] (cellulose nitrate) which was historically used in [[smokeless powder|smokeless gunpowder]] and as the base material for [[celluloid]] used for photographic and movie films until the mid 1930s. [[Cellulose insulation]] made from recycled newsprint is becoming popular as an environmentally preferable material for [[building insulation]]. Cellulose is used to make [[hydrophilic]] and highly absorbent sponges, as well as water-soluble [[adhesives]] and [[binder (material)|binders]] such as [[methyl cellulose]] and [[carboxymethyl cellulose]] which are used in [[wallpaper]] paste. [[Microcrystalline cellulose]] ([[E number|E460i]]) and powdered cellulose (E460ii) are used as inactive fillers in tablets and as thickeners and stabilizers in processed foods. === Cellulose source and energy crops === {{Main|Energy crop}} The major [[combustion|combustible]] component of non-food [[energy crop]]s is cellulose, with [[lignin]] second. Non-food energy crops are more [[sustainable]] than edible energy crops (which have a large [[starch]] component), but still compete with food crops for agricultural land and water resources.<ref>Holt-Gimenez, Eric 2007. Biofuels: Myths of the Agrofuels Transition. ''Backgrounder.'' Institute for Food and Development Policy, Oakland, CA. 13:2</ref> Typical non-food energy crops include [[hemp|industrial hemp]], [[switchgrass]], ''[[Miscanthus]]'', ''Salix'' ([[willow]]), and ''Populus'' ([[poplar]]) species. Some bacteria can convert cellulose into [[ethanol]] which can then be used as a fuel; see [[cellulosic ethanol]]. [[Image:Cellulose strand.jpg|thumb|right|260px|A strand of cellulose, showing the [[hydrogen bond]]s within and between cellulose molecules (dashed).]] ==Structure and properties== Cellulose has no taste, is odourless, is [[hydrophilic]], is insoluble in [[water]] and most organic [[solvent]]s, is [[Chirality (chemistry)|chiral]] and it is biodegradable. Cellulose is derived from <small>D</small>-glucose units, which [[condensation reaction|condense]] through β(1→4)-[[glycosidic bond]]s. This linkage motif contrasts with that for α(1→4)-glycosidic bonds present in [[starch]], [[glycogen]], and other carbohydrates. Cellulose is a straight chain polymer: unlike starch, no coiling occurs, and the molecule adopts an extended and rather stiff rod-like conformation. The multiple [[hydroxyl|hydroxyl groups]] on the glucose residues from one chain form [[hydrogen bond]]s with oxygen molecules on another chain, holding the chains firmly together side-by-side and forming ''microfibrils'' with high [[tensile strength]]. This strength is important in cell walls, where they are meshed into a carbohydrate ''matrix'', conferring rigidity to plant cells. Compared to starch, cellulose is also much more [[crystallinity|crystalline]]. Whereas starch undergoes a crystalline to [[amorphous solid|amorphous]] transition when heated beyond 60-70 °C in water (as in cooking), cellulose requires a temperature of 320 °C and pressure of 25 [[Pascal (unit)|MPa]] to become amorphous in water.<ref name=Deguchi>''Cooking cellulose in hot and compressed water'' Shigeru Deguchi, Kaoru Tsujii and Koki Horikoshi [[Chem. Commun.]], '''2006''', 3293 - 3295, {{DOI|10.1039/b605812d}}</ref> Chemically, cellulose can be broken down into its glucose units by treating it with concentrated acids at high temperature. Many properties of cellulose depend on its [[degree of polymerization]] or chain length, the number of glucose units that make up one polymer molecule. Cellulose from wood pulp has typical chain lengths between 300 and 1700 units; cotton and other plant fibers as well as bacterial celluloses have chain lengths ranging from 800 to 10,000 units.<ref name=Klemm/> Molecules with very small chain length resulting from the break down of cellulose are known as [[cellodextrin]]s; in contrast to long-chain cellulose, cellodextrins are typically soluble in water and organic solvents. Plant-derived cellulose is usually contaminated with [[hemicellulose]], [[lignin]], [[pectin]] and other substances, while [[microbial cellulose]] is quite pure, has a much higher water content, and consists of long chains. ==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 acid|acetic]] and [[nitric acid]] to remove lignin, hemicellulose, and xylosans. The resulting cellulose is allowed to react with [[anthrone]] in [[sulfuric acid]]. The resulting coloured compound is assayed [[spectrophotometry|spectrophotometrically]] at a wavelength of approximately 635 [[1 E-9 m|nm]]. In addition, cellulose is represented by the difference between acid detergent fiber (ADF) and acid detergent lignin (ADL). == Biosynthesis == [[Image:Plant cell wall diagram.svg|thumb|250px|right|Location and arrangement of cellulose microfibrils in the plant [[cell wall]].]] In [[vascular plant]]s cellulose is synthesized at the [[plasma membrane]] by rosette terminal complexes (RTC's). The RTC's are [[oligomer|hexameric]] protein structures, approximately 25 [[nanometre|nm]] in diameter, that contain the cellulose [[synthase]] enzymes that synthesise the individual cellulose chains.<ref>Kimura, Laosinchai, Itoh, Cui, Linder, Brown, ''Plant Cell'', 1999, 11, '''2075-2085</ref> Each RTC floats in the cell's plasma membrane and "spins" a microfibril into the cell wall. The RTC's contain at least three different cellulose synthases, encoded by ''CesA'' genes, in an unknown [[stoichiometry]].<ref>Taylor, Howells, Huttly, Vickers, Turner, ''PNAS'', 2003, '''100''', 1450-1455</ref> Separate sets of ''CesA'' genes are involved in primary and secondary [[cell wall]] biosynthesis. [[cellulose synthase (UDP-forming)|Cellulose synthase]] utilizes [[Uridine diphosphate|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.<ref>Peng, Kawagoe, Hogan, Delmer, ''Science'', 2002, '''295''', 147-150.</ref> A [[cellulase]] may function to cleave the primer from the mature chain. ==Breakdown (cellulolysis)== Cellulolysis is the process of breaking down cellulose into smaller polysaccharides called [[cellodextrins]] or completely into glucose units; this is a [[hydrolysis]] reaction. Because cellulose molecules bind strongly to each other, cellulolysis is relatively difficult compared to the break down of other polysaccharides.<ref>David G. Barkalow, Roy L. Whistler, "Cellulose", in AccessScience@McGraw-Hill, DOI 10.1036/1097-8542.118200. Retrieved 11 January 2008.</ref> Mammals do not have the ability to break down cellulose directly. Some [[ruminant]]s like cows and sheep contain certain [[symbiosis|symbiotic]] [[anaerobic]] bacteria (like ''[[Cellulomonas]]'') in the flora of the gut wall, and these bacteria produce [[enzyme]]s to break down cellulose; the break down products are then used by the mammal. Similarly, lower [[termite]]s contain in their [[hindgut]]s certain [[flagellate]] [[protozoa]] which produce such enzymes; higher termites contain bacteria for the job. [[Fungus|Fungi]], which in nature are responsible for recycling of nutrients, are also able to break down cellulose. The enzymes utilized to [[wikt:cleave|cleave]] the [[glycosidic linkage]] in cellulose are [[glycoside hydrolase]]s including endo-acting [[cellulase]]s and exo-acting [[glucosidase]]s. Such enzymes are usually secreted as part of multienzyme complexes that may include [[dockerin]]s and cellulose binding modules; these complexes are in some cases referred to as [[cellulosome]]s. ==Hemicellulose== [[Hemicellulose]] is a polysaccharide related to cellulose that comprises ca. 20% of the biomass of most plants. In contrast to cellulose, hemicellulose is derived from several sugars in addition to glucose, including especially [[xylose]] but also [[mannose]], [[galactose]], [[rhamnose]], and [[arabinose]]. Hemicellulose consists of shorter chains - around 200 sugar units as opposed to 7,000 - 15,000 glucose molecules in the average cellulose polymer. Furthermore, hemicellulose is branched, whereas cellulose is unbranched. ==Derivatives== The [[hydroxyl]] groups of cellulose can be partially or fully reacted with various [[reagent]]s to afford derivatives with useful properties. Cellulose [[ester]]s and cellulose [[ether]]s 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]], [[E number|E464]], used as a viscosity modifier, gelling agent, foaming agent and binding agent; * Hydroxyethyl methyl cellulose, used in production of cellulose films. ==References== {{reflist}} ==See also== * [[Cell wall]] * [[Cellulose insulation]] * [[Cellulosic ethanol]] * [[Cellulosic ethanol commercialization]] * [[Hemicellulose]] * [[Microbial cellulose]] ==External links== * [http://www.lsbu.ac.uk/water/hycel.html LSBU cellulose page] * [http://msa.ars.usda.gov/la/srrc/fb/ca.html Clear description of a cellulose assay method] at the Cotton Fiber Biosciences unit of the [[United States Department of Agriculture|USDA]]. * [http://www.technologyreview.com/read_article.aspx?ch=infotech&sc=&id=17127&pg=1 Cellulose films could provide flapping wings and cheap artificial muscles for robots] - TechnologyReview.com * [http://www1.eere.energy.gov/biomass/cellulase_enzyme.html Using cellulase enzymes in the bioethanol process]. * [http://www.wzw.tum.de/mbiotec/cellmo.htm A list of cellulolytic bacteria]. * [http://www.disposablediaper.net/content.asp?14 Manufacturers of fluff cellulose all over the world] {{carbohydrates}} [[Category:Polysaccharides]] [[Category:Cellulose| ]] [[ar:سليولوز]] [[bs:Celuloza]] [[bg:Целулоза]] [[ca:Cel·lulosa]] [[cs:Celulóza]] [[da:Cellulose]] [[de:Cellulose]] [[et:Tselluloos]] [[es:Celulosa]] [[eo:Celulozo]] [[fa:سلولز]] [[fr:Cellulose]] [[hr:Celuloza]] [[io:Celulozo]] [[id:Selulosa]] [[is:Sellulósi]] [[it:Cellulosa]] [[he:תאית]] [[lt:Celiuliozė]] [[hu:Cellulóz]] [[mk:Целулоза]] [[ms:Selulosa]] [[nl:Cellulose]] [[ja:セルロース]] [[no:Cellulose]] [[nn:Cellulose]] [[oc:Cellulòsa]] [[pl:Celuloza]] [[pt:Celulose]] [[qu:Silulusa]] [[ru:Целлюлоза]] [[sq:Celuloza]] [[simple:Cellulose]] [[sk:Celulóza (organická látka)]] [[sl:Celuloza]] [[sr:Целулоза]] [[sh:Celuloza]] [[su:Selulosa]] [[fi:Selluloosa]] [[sv:Cellulosa]] [[ta:மாவியம்]] [[th:เซลลูโลส]] [[vi:Cellulose]] [[tr:Selüloz]] [[uk:Целюлоза]] [[zh:纤维素]]