52-459: The Mesotaeniaceae are a small family of unicellular green algae known as the "saccoderm desmids". The Mesotaeniaceae appear to be sister or ancestral to the Zygnemataceae . The desmids are a deep branching group of Zygnemataceae. Spirotaenia was found to be a basal green alga. The Mesotaeniaceae includes the following genera: Synonyms: This green algae -related article
104-454: A crystalline to amorphous transition when heated beyond 60–70 °C in water (as in cooking), cellulose requires a temperature of 320 °C and pressure of 25 MPa to become amorphous in water. Several types of cellulose are known. These forms are distinguished according to the location of hydrogen bonds between and within strands. Natural cellulose is cellulose I, with structures I α and I β . Cellulose produced by bacteria and algae
156-414: A group of photosynthetic, eukaryotic organisms that include species with haplobiontic and diplobiontic life cycles. The diplobiontic species, such as Ulva , follow a reproductive cycle called alternation of generations in which two multicellular forms, haploid and diploid, alternate, and these may or may not be isomorphic (having the same morphology). In haplobiontic species only the haploid generation,
208-467: A liquid called bio-oil is obtained at 500 °C. Semi-crystalline cellulose polymers react at pyrolysis temperatures (350–600 °C) in a few seconds; this transformation has been shown to occur via a solid-to-liquid-to-vapor transition, with the liquid (called intermediate liquid cellulose or molten cellulose ) existing for only a fraction of a second. Glycosidic bond cleavage produces short cellulose chains of two-to-seven monomers comprising
260-469: A multicellular gametophyte. All land plants have a diplobiontic common ancestor, and diplobiontic forms have also evolved independently within Ulvophyceae more than once (as has also occurred in the red and brown algae). Diplobiontic green algae include isomorphic and heteromorphic forms. In isomorphic algae, the morphology is identical in the haploid and diploid generations. In heteromorphic algae,
312-409: A polysaccharide matrix . The high tensile strength of plant stems and of the tree wood also arises from the arrangement of cellulose fibers intimately distributed into the lignin matrix. The mechanical role of cellulose fibers in the wood matrix responsible for its strong structural resistance, can somewhat be compared to that of the reinforcement bars in concrete , lignin playing here the role of
364-419: A proper solvent , e.g. in an ionic liquid . Most mammals have limited ability to digest dietary fibre such as cellulose. Some ruminants like cows and sheep contain certain symbiotic anaerobic bacteria (such as Cellulomonas and Ruminococcus spp. ) in the flora of the rumen , and these bacteria produce enzymes called cellulases that hydrolyze cellulose. The breakdown products are then used by
416-1012: A sister of the Zygnematophyceae . Since the realization that the Embryophytes emerged within the green algae, some authors are starting to include them. The completed clade that includes both green algae and embryophytes is monophyletic and is referred to as the clade Viridiplantae and as the kingdom Plantae . The green algae include unicellular and colonial flagellates , most with two flagella per cell, as well as various colonial, coccoid (spherical), and filamentous forms, and macroscopic, multicellular seaweeds . There are about 22,000 species of green algae, many of which live most of their lives as single cells, while other species form coenobia (colonies), long filaments, or highly differentiated macroscopic seaweeds. A few other organisms rely on green algae to conduct photosynthesis for them. The chloroplasts in dinoflagellates of
468-744: A variety of uses. Nitrocellulose was initially used as an explosive and was an early film forming material. When plasticized with camphor , nitrocellulose gives celluloid . Cellulose Ether derivatives include: The sodium carboxymethyl cellulose can be cross-linked to give the croscarmellose sodium (E468) for use as a disintegrant in pharmaceutical formulations. Furthermore, by the covalent attachment of thiol groups to cellulose ethers such as sodium carboxymethyl cellulose, ethyl cellulose or hydroxyethyl cellulose mucoadhesive and permeation enhancing properties can be introduced. Thiolated cellulose derivatives (see thiomers ) exhibit also high binding properties for metal ions. Cellulose for industrial use
520-464: A wide variety of derivative products such as cellophane and rayon . Conversion of cellulose from energy crops into biofuels such as cellulosic ethanol is under development as a renewable fuel source. Cellulose for industrial use is mainly obtained from wood pulp and cotton . Cellulose is also greatly affected by direct interaction with several organic liquids. Some animals, particularly ruminants and termites , can digest cellulose with
572-685: A wide variety of products. While the first application of regenerated cellulose was as a clothing textile , this class of materials is also used in the production of disposable medical devices as well as fabrication of artificial membranes . The hydroxyl groups (−OH) of cellulose can be partially or fully reacted with various reagents to afford derivatives with useful properties like mainly cellulose esters and cellulose ethers (−OR). In principle, although not always in current industrial practice, cellulosic polymers are renewable resources. Ester derivatives include: Cellulose acetate and cellulose triacetate are film- and fiber-forming materials that find
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#1732793593342624-698: Is (C 6 H 10 O 5 ) n where n is the degree of polymerization and represents the number of glucose groups. Plant-derived cellulose is usually found in a mixture with hemicellulose , lignin , pectin and other substances, while bacterial cellulose is quite pure, has a much higher water content and higher tensile strength due to higher chain lengths. Cellulose consists of fibrils with crystalline and amorphous regions. These cellulose fibrils may be individualized by mechanical treatment of cellulose pulp, often assisted by chemical oxidation or enzymatic treatment, yielding semi-flexible cellulose nanofibrils generally 200 nm to 1 μm in length depending on
676-523: Is a stub . You can help Misplaced Pages by expanding it . Green alga The green algae ( sg. : green alga ) are a group of chlorophyll -containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta / Streptophyta . The land plants ( Embryophytes ) have emerged deep in the Charophyte alga as
728-546: Is a straight chain polymer. Unlike starch, no coiling or branching occurs and the molecule adopts an extended and rather stiff rod-like conformation, aided by the equatorial conformation of the glucose residues. The multiple hydroxyl groups on the glucose from one chain form hydrogen bonds with oxygen atoms on the same or on a neighbour chain, holding the chains firmly together side-by-side and forming microfibrils with high tensile strength . This confers tensile strength in cell walls where cellulose microfibrils are meshed into
780-468: Is a unicellular, isogamous charophycean alga group that is the closest unicellular relative to land plants. Heterothallic strains of different mating type can conjugate to form zygospores . Sex pheromones termed protoplast-release inducing proteins (glycopolypeptides) produced by mating-type (-) and mating-type (+) cells facilitate this process. The green algae, including the characean algae, have served as model experimental organisms to understand
832-470: Is an important 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 biofilms . Cellulose is the most abundant organic polymer on Earth. The cellulose content of cotton fibre is 90%, that of wood is 40–50%, and that of dried hemp is approximately 57%. Cellulose is mainly used to produce paperboard and paper . Smaller quantities are converted into
884-473: Is enriched in I α while cellulose of higher plants consists mainly of I β . Cellulose in regenerated cellulose fibers is cellulose II. The conversion of cellulose I to cellulose II is irreversible, suggesting that cellulose I is metastable and cellulose II is stable. With various chemical treatments it is possible to produce the structures cellulose III and cellulose IV. Many properties of cellulose depend on its chain length or degree of polymerization ,
936-665: Is mainly obtained from wood pulp and from cotton . Energy crops: The major combustible component of non-food energy crops is cellulose, with lignin second. Non-food energy crops produce more usable energy than edible energy crops (which have a large starch component), but still compete with food crops for agricultural land and water resources. Typical non-food energy crops include industrial hemp , switchgrass , Miscanthus , Salix ( willow ), and Populus ( poplar ) species. A strain of Clostridium bacteria found in zebra dung, can convert nearly any form of cellulose into butanol fuel . Another possible application
988-591: Is odorless, is hydrophilic with the contact angle of 20–30 degrees, is insoluble in water and most organic solvents , is chiral and is biodegradable . It was shown to melt at 467 °C in pulse tests made by Dauenhauer et al. (2016). It can be broken down chemically into its glucose units by treating it with concentrated mineral acids at high temperature. Cellulose is derived from D -glucose units, which condense through β(1→4)- glycosidic bonds . This linkage motif contrasts with that for α(1→4)-glycosidic bonds present in starch and glycogen . Cellulose
1040-405: Is produced using the same family of proteins, although the gene is called BcsA for "bacterial cellulose synthase" or CelA for "cellulose" in many instances. In fact, plants acquired CesA from the endosymbiosis event that produced the chloroplast . All cellulose synthases known belongs to glucosyltransferase family 2 (GT2). Cellulose synthesis requires chain initiation and elongation, and
1092-448: Is short for "cellulose synthase") genes, in an unknown stoichiometry . Separate sets of CesA genes are involved in primary and secondary cell wall biosynthesis. There are known to be about seven subfamilies in the plant CesA superfamily, some of which include the more cryptic, tentatively-named Csl (cellulose synthase-like) enzymes. These cellulose syntheses use UDP-glucose to form the β(1→4)-linked cellulose. Bacterial cellulose
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#17327935933421144-434: Is synthesized at the plasma membrane by rosette terminal complexes (RTCs). The RTCs are hexameric protein structures, approximately 25 nm in diameter, that contain the cellulose synthase enzymes that synthesise the individual cellulose chains. Each RTC floats in the cell's plasma membrane and "spins" a microfibril into the cell wall . RTCs contain at least three different cellulose synthases , encoded by CesA ( Ces
1196-433: The (green) plants (with chloroplasts ) the red algae (with rhodoplasts) and the glaucophytes (with muroplasts). Green algae are often classified with their embryophyte descendants in the green plant clade Viridiplantae (or Chlorobionta ). Viridiplantae, together with red algae and glaucophyte algae, form the supergroup Primoplantae, also known as Archaeplastida or Plantae sensu lato . The ancestral green alga
1248-497: The gametophyte is multicellular. The fertilized egg cell, the diploid zygote , undergoes meiosis , giving rise to haploid cells which will become new gametophytes. The diplobiontic forms, which evolved from haplobiontic ancestors, have both a multicellular haploid generation and a multicellular diploid generation. Here the zygote divides repeatedly by mitosis and grows into a multicellular diploid sporophyte . The sporophyte produces haploid spores by meiosis that germinate to produce
1300-495: 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 carbohydrate-binding modules . At temperatures above 350 °C, cellulose undergoes thermolysis (also called ' pyrolysis '), decomposing into solid char , vapors, aerosols , and gases such as carbon dioxide . Maximum yield of vapors which condense to
1352-412: The hardened cement paste acting as the "glue" in between the cellulose fibres. Mechanical properties of cellulose in primary plant cell wall are correlated with growth and expansion of plant cells. Live fluorescence microscopy techniques are promising in investigation of the role of cellulose in growing plant cells. Compared to starch, cellulose is also much more crystalline . Whereas starch undergoes
1404-507: The supralittoral zone , is terrestrial and can in the Antarctic form large carpets on humid soil, especially near bird colonies. Green algae have chloroplasts that contain chlorophyll a and b , giving them a bright green colour, as well as the accessory pigments beta carotene (red-orange) and xanthophylls (yellow) in stacked thylakoids . The cell walls of green algae usually contain cellulose , and they store carbohydrate in
1456-723: The Mesostigmatophyceae, Chlorokybophyceae and spirotaenia are only more conventionally basal Streptophytes. The algae of this paraphyletic group "Charophyta" were previously included in Chlorophyta, so green algae and Chlorophyta in this definition were synonyms. As the green algae clades get further resolved, the embryophytes, which are a deep charophyte branch, are included in " algae ", "green algae" and " Charophytes ", or these terms are replaced by cladistic terminology such as Archaeplastida , Plantae / Viridiplantae , and streptophytes , respectively. Green algae are
1508-536: The Viscose Development Company, is the most widely used method for manufacturing regenerated cellulose products. Courtaulds purchased the patents for this process in 1904, leading to significant growth of viscose fiber production. By 1931, expiration of patents for the viscose process led to its adoption worldwide. Global production of regenerated cellulose fiber peaked in 1973 at 3,856,000 tons. Regenerated cellulose can be used to manufacture
1560-410: The bacteria for proliferation. The bacterial mass is later digested by the ruminant in its digestive system ( stomach and small intestine ). Horses use cellulose in their diet by fermentation in their hindgut . Some termites contain in their hindguts certain flagellate protozoa producing such enzymes, whereas others contain bacteria or may produce cellulase. The enzymes used to cleave
1612-446: The basis of commercial technologies. These dissolution processes are reversible and are used in the production of regenerated celluloses (such as viscose and cellophane ) from dissolving pulp . The most important solubilizing agent is carbon disulfide in the presence of alkali. Other agents include Schweizer's reagent , N -methylmorpholine N -oxide , and lithium chloride in dimethylacetamide . In general, these agents modify
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1664-450: The biomass of land plants . In contrast to cellulose, hemicelluloses are derived from several sugars in addition to glucose , especially xylose but also including mannose , galactose , rhamnose , and arabinose . Hemicelluloses consist of shorter chains – between 500 and 3000 sugar units. Furthermore, hemicelluloses are branched, whereas cellulose is unbranched. Cellulose is soluble in several kinds of media, several of which are
1716-446: The cellulose was historically termed "tunicine" (tunicin)). 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 breakdown of other polysaccharides . However, this process can be significantly intensified in
1768-557: The cellulose, rendering it soluble. The agents are then removed concomitant with the formation of fibers. Cellulose is also soluble in many kinds of ionic liquids . The history of regenerated cellulose is often cited as beginning with George Audemars, who first manufactured regenerated nitrocellulose fibers in 1855. Although these fibers were soft and strong -resembling silk- they had the drawback of being highly flammable. Hilaire de Chardonnet perfected production of nitrocellulose fibers, but manufacturing of these fibers by his process
1820-413: The class Chlorophyceae undergo closed mitosis in the most common form of cell division among the green algae, which occurs via a phycoplast . By contrast, charophyte green algae and land plants (embryophytes) undergo open mitosis without centrioles . Instead, a 'raft' of microtubules, the phragmoplast , is formed from the mitotic spindle and cell division involves the use of this phragmoplast in
1872-427: The form of starch . All green algae have mitochondria with flat cristae . When present, paired flagella are used to move the cell. They are anchored by a cross-shaped system of microtubules and fibrous strands. Flagella are only present in the motile male gametes of charophytes bryophytes, pteridophytes, cycads and Ginkgo , but are absent from the gametes of Pinophyta and flowering plants . Members of
1924-435: The fungal species that partner in lichens cannot live on their own, while the algal species is often found living in nature without the fungus. Trentepohlia is a filamentous green alga that can live independently on humid soil, rocks or tree bark or form the photosymbiont in lichens of the family Graphidaceae . Also the macroalga Prasiola calophylla (Trebouxiophyceae) is terrestrial, and Prasiola crispa , which live in
1976-584: The genus Lepidodinium , euglenids and chlorarachniophytes were acquired from ingested endosymbiont green algae, and in the latter retain a nucleomorph (vestigial nucleus). Green algae are also found symbiotically in the ciliate Paramecium , and in Hydra viridissima and in flatworms . Some species of green algae, particularly of genera Trebouxia of the class Trebouxiophyceae and Trentepohlia (class Ulvophyceae ), can be found in symbiotic associations with fungi to form lichens . In general
2028-402: The heat of late summer. As their environment dries out, asexual V. carteri quickly die. However, they are able to escape death by switching, shortly before drying is complete, to the sexual phase of their life cycle that leads to production of dormant desiccation-resistant zygotes . Sexual development is initiated by a glycoprotein pheromone (Hallmann et al., 1998). This pheromone is one of
2080-491: The help of symbiotic micro-organisms that live in their guts, such as Trichonympha . In human nutrition , cellulose is a non-digestible constituent of insoluble dietary fiber , acting as a hydrophilic bulking agent for feces and potentially aiding in defecation . Cellulose was discovered in 1838 by the French chemist Anselme Payen , who isolated it from plant matter and determined its chemical formula. Cellulose
2132-516: The light microscope. This process is called conjugation and occurs for example in Spirogyra . Sex pheromone production is likely a common feature of green algae, although only studied in detail in a few model organisms. Volvox is a genus of chlorophytes . Different species form spherical colonies of up to 50,000 cells. One well-studied species, Volvox carteri (2,000 – 6,000 cells) occupies temporary pools of water that tend to dry out in
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2184-460: The mechanisms of the ionic and water permeability of membranes, osmoregulation , turgor regulation, salt tolerance , cytoplasmic streaming , and the generation of action potentials . Cellulose Cellulose is an organic compound with the formula ( C 6 H 10 O 5 ) n , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D -glucose units. Cellulose
2236-602: The melt. Vapor bubbling of intermediate liquid cellulose produces aerosols , which consist of short chain anhydro-oligomers derived from the melt. Continuing decomposition of molten cellulose produces volatile compounds including levoglucosan , furans , pyrans , light oxygenates, and gases via primary reactions. Within thick cellulose samples, volatile compounds such as levoglucosan undergo 'secondary reactions' to volatile products including pyrans and light oxygenates such as glycolaldehyde . Hemicelluloses are polysaccharides related to cellulose that comprises about 20% of
2288-587: The morphology and size are different in the gametophyte and sporophyte. Reproduction varies from fusion of identical cells ( isogamy ) to fertilization of a large non-motile cell by a smaller motile one ( oogamy ). However, these traits show some variation, most notably among the basal green algae called prasinophytes . Haploid algal cells (containing only one copy of their DNA) can fuse with other haploid cells to form diploid zygotes. When filamentous algae do this, they form bridges between cells, and leave empty cell walls behind that can be easily distinguished under
2340-417: The most potent known biological effector molecules. It can trigger sexual development at concentrations as low as 10 M. Kirk and Kirk showed that sex-inducing pheromone production can be triggered experimentally in somatic cells by heat shock . Thus heat shock may be a condition that ordinarily triggers sex-inducing pheromone in nature. The Closterium peracerosum-strigosum-littorale (C. psl) complex
2392-508: 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 cellulose have chain lengths ranging from 800 to 10,000 units. Molecules with very small chain length resulting from the breakdown of cellulose are known as cellodextrins ; in contrast to long-chain cellulose, cellodextrins are typically soluble in water and organic solvents. The chemical formula of cellulose
2444-413: The production of a cell plate . Photosynthetic eukaryotes originated following a primary endosymbiotic event, where a heterotrophic eukaryotic cell engulfed a photosynthetic cyanobacterium -like prokaryote that became stably integrated and eventually evolved into a membrane-bound organelle : the plastid . This primary endosymbiosis event gave rise to three autotrophic clades with primary plastids:
2496-524: The treatment intensity. Cellulose pulp may also be treated with strong acid to hydrolyze the amorphous fibril regions, thereby producing short rigid cellulose nanocrystals a few 100 nm in length. These nanocelluloses are of high technological interest due to their self-assembly into cholesteric liquid crystals , production of hydrogels or aerogels , use in nanocomposites with superior thermal and mechanical properties, and use as Pickering stabilizers for emulsions . In plants cellulose
2548-430: The two processes are separate. Cellulose synthase ( CesA ) initiates cellulose polymerization using a steroid primer, sitosterol -beta- glucoside , and UDP-glucose. It then utilises UDP -D-glucose precursors to elongate the growing cellulose chain. A cellulase may function to cleave the primer from the mature chain. Cellulose is also synthesised by tunicate animals, particularly in the tests of ascidians (where
2600-963: Was a unicellular flagellate. The Viridiplantae diverged into two clades. The Chlorophyta include the early diverging prasinophyte lineages and the core Chlorophyta, which contain the majority of described species of green algae. The Streptophyta include charophytes and land plants. Below is a consensus reconstruction of green algal relationships, mainly based on molecular data. Palmophyllophyceae (prasinophyte clade VI) Prasinodermophyceae Ulvophyceae Chlorophyceae Trebouxiophyceae Chlorodendrophyceae Pedinophyceae Prasinophytes Clade VIIA Prasinophytes Clade VIIC Pycnococcaceae Nephroselmidophyceae Mamiellophyceae Pyramimonadales Mesostigmatophyceae Spirotaenia Chlorokybophyceae Streptofilum Klebsormidiophyceae Charophyceae Coleochaetophyceae Zygnematophyceae Mesotaeniaceae s.s. Embryophyta (land plants) The basal character of
2652-409: Was relatively uneconomical. In 1890, L.H. Despeissis invented the cuprammonium process – which uses a cuprammonium solution to solubilize cellulose – a method still used today for production of artificial silk . In 1891, it was discovered that treatment of cellulose with alkali and carbon disulfide generated a soluble cellulose derivative known as viscose . This process, patented by the founders of
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#17327935933422704-473: Was used to produce the first successful thermoplastic polymer , celluloid , by Hyatt Manufacturing Company in 1870. Production of rayon ("artificial silk ") from cellulose began in the 1890s and cellophane was invented in 1912. Hermann Staudinger determined the polymer structure of cellulose in 1920. The compound was first chemically synthesized (without the use of any biologically derived enzymes ) in 1992, by Kobayashi and Shoda. Cellulose has no taste,
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