Скроб — разлика између измена
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| verifiedrevid = 455316358
| ImageFile = Cornstarch_mixed_with_water.jpg
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| CASNo = 9005-25-8
| CASNo_Ref = {{cascite|correct|CAS}}
| EC_number = 232-679-6
| RTECS = GM5090000
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
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|Section2={{Chembox Properties
| Formula = ({{chem|C|6|H|10|O|5|)|''n''</sub> -{{Sp}}|(|H|2|O|)}}
| MolarMass = Варијабилна
| Appearance = Бели прах
| Density = Варијабилна<ref>{{cite book | title = Starch: Chemistry and Technology | editor1 = Roy L. Whistler|editor2=James N. BeMiller|editor3=Eugene F. Paschall | publisher = Academic Press | date = 2012 | page = 220 | quote = Starch has variable density depending on botanical origin, prior treatment, and method of measurement }}</ref>
| Solubility = нерастворан
| MeltingPt = разлаже се
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| Section4 = {{Chembox Thermochemistry
| Thermochemistry_ref =
| HeatCapacity =
| Entropy =
| DeltaHf =
| DeltaGf =
| DeltaHc ={{convert|4.1788|kcal/g|kJ/g}}<ref name=CRC>''[[CRC Handbook of Chemistry and Physics]]'', 49th edition, 1968-1969, p. D-188.</ref>
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|Section7={{Chembox Hazards
| ExternalSDS = [http://www.inchem.org/documents/icsc/icsc/eics1553.htm ICSC 1553]
| AutoignitionPtC = 410
| PEL = -{TWA 15 mg/m}-<sup>3</sup> (укупно) -{TWA 5 mg/m}-<sup>3</sup><ref>{{PGCH|0567}}</ref>
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[[File:Amylose2.svg|thumb|right|260px|Структура молекула [[amylose|амилозе]]]]
[[File:Amylopektin Sessel.svg|thumb|right|260px|Структура молекула [[амилопектин]]а]]
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'''Скроб''' ({{јез-лат|amylum}}) је природни [[полисахариди|полисахарид]] опште формуле -{(C<sub>6</sub>H<sub>10</sub>O<sub>5</sub>)n</sub>}-. Налази се у [[воће|воћу]], семенкама, корењу, кртолама и лишћу [[биљке|биљака]].<ref name="uh">{{Cite web|url=http://www.topforma.co.yu/ugljeni%20hidrati/ugljeni%20hidrati.html|title=Угљени хидрати|accessdate=9. 2. 2008.|last=|first=|coauthors=|date=|work=|publisher=|archive-url=https://web.archive.org/web/20080222022947/http://www.topforma.co.yu/ugljeni%20hidrati/ugljeni%20hidrati.html|archive-date=22. 02. 2008|dead-url=yes|df=}}</ref> То је један од основних састојака [[храна|хране]] и производе га искључиво биљке, којима скроб служи као резервна енергија. По улози и структури је сличан [[гликоген]]у који исту функцију обавља код [[животиње|животиња]].
Pure starch is a white, tasteless and odorless powder that is insoluble in cold water or alcohol. It consists of two types of molecules: the linear and [[helix|helical]] [[amylose]] and the branched [[amylopectin]]. Depending on the plant, starch generally contains 20 to 25% amylose and 75 to 80% amylopectin by weight.<ref>{{Cite book |last1=Brown |first1=W. H. |last2=Poon |first2=T. |year=2005 |title=Introduction to organic chemistry |edition=3rd |publisher=Wiley |isbn=978-0-471-44451-0}}</ref> [[Glycogen]], the glucose store of animals, is a more highly branched version of amylopectin.
In industry, starch is converted into sugars, for example by [[malt]]ing, and [[fermentation|fermented]] to produce [[ethanol]] in the manufacture of [[beer]], [[whisky]] and [[biofuel]]. It is processed to produce many of the sugars used in processed foods. Mixing most starches in warm water produces a paste, such as [[wheatpaste]], which can be used as a thickening, stiffening or gluing agent. The biggest industrial non-food use of starch is as an adhesive in the [[papermaking]] process. Starch can be applied to parts of some garments before ironing, to [[#Clothing starch|stiffen them]].
== Историја ==
Starch grains from the [[rhizome]]s of ''[[Typha]]'' (cattails, bullrushes) as [[flour]] have been identified from [[grinding stone]]s in Europe dating back to 30,000 years ago.<ref name="Revedin">{{cite journal |doi=10.1073/pnas.1006993107 |title=Thirty thousand-year-old evidence of plant food processing |year=2010 |last1=Revedin |first1=A. |last2=Aranguren |first2=B. |last3=Becattini |first3=R. |last4=Longo |first4=L. |last5=Marconi |first5=E. |last6=Lippi |first6=M. M. |last7=Skakun |first7=N. |last8=Sinitsyn |first8=A. |last9=Spiridonova |first9=E. |last10=Svoboda |first10=J. |journal=Proceedings of the National Academy of Sciences |volume=107 |issue=44 |pmid=20956317 |pages=18815–9 |pmc=2973873|display-authors=8 }}</ref> Starch grains from [[sorghum]] were found on grind stones in caves in [[Ngalue]], [[Mozambique]] dating up to 100,000 years ago.<ref>{{cite news|newspaper=The Telegraph|title=Porridge was eaten 100,000 years ago|date=18 Dec 2009|url=https://www.telegraph.co.uk/news/uknews/6834609/Porridge-was-eaten-100000-years-ago.html}}</ref>
Pure extracted wheat starch paste was used in [[Ancient Egypt]] possibly to glue [[papyrus]].<ref>[[Pliny the Elder]], The ''[[Natural History (Pliny)]]'', Book XIII, Chapter 26, [http://www.perseus.tufts.edu/cgi-bin/ptext?doc=Perseus%3Atext%3A1999.02.0137&query=head%3D%23817 The paste used in preparation of paper]</ref> The extraction of starch is first described in the ''[[Natural History (Pliny)|Natural History]]'' of [[Pliny the Elder]] around AD 77–79.<ref>[[Pliny the Elder]], The [[Natural History (Pliny)]], Book XIII, Chapter 17, [http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.02.0137%3Abook%3D18%3Achapter%3D17]</ref> Romans used it also in cosmetic creams, to powder the hair and to thicken sauces. Persians and Indians used it to make dishes similar to gothumai wheat [[halva]]. Rice starch as surface treatment of paper has been used in paper production in China since 700 [[Common Era|CE]].<ref>{{cite book |first=Dard |last=Hunter |year=1947 |title=Papermaking |publisher=DoverPublications |isbn=978-0-486-23619-3 |page=194}}</ref>
== Индустрија скроба ==
In addition to starchy plants consumed directly, by 2008 66 million tonnes of starch were being produced per year worldwide. In 2011 production was increased to 73 million ton. <ref>[https://www.starch.eu/blog/2013/05/15/aaf-position-on-trade-and-competitiveness/ Starch Europe, AAF position on competitiveness, visited march 3 2019]</ref>
In the [[European Union|EU]] the [[starch production|starch industry]] produced about 8.5 million tonnes in 2008, with around 40% being used for industrial applications and 60% for food uses,<ref name=nnfcc>[http://www.nnfcc.co.uk/publications/nnfcc-renewable-chemicals-factsheet-starch NNFCC Renewable Chemicals Factsheet: Starch]</ref> most of the latter as [[glucose syrup]]s.<ref>International Starch Institute Denmark, [http://www.starch.dk/isi/market/index.asp Starch production volume]</ref> In 2017 EU production was 11 million ton of which 9,4 million ton was consumed in the EU and of which 54% were starch sweeteners.<ref>[https://www.starch.eu/the-european-starch-industry/ Starch Europe, Industry, visited march 3 2019]</ref>
[[United States of America|US]] produced about 27,5 million ton starch in 2017 of which about 8,2 million ton [[high fructose syrup]] and 6,2 million ton glucose syrups and 2,5 million ton starch products, the rest of the starch was used for producing [[ethanol]] (1,6 billion gallon or 7,3 billion liter of ethanol). <ref>[https://corn.org/wp-content/uploads/2018/04/CRA-Industry-Overview-2017.pdf CRA, Industry overview 2017, visited on march 3 2019 ]</ref><ref>[https://www.starch.eu/blog/2015/02/27/position-on-the-eu-us-ttip/#return-note-11608-4 Starch Europe, Updated position on the EU-US Transatlantic Trade and Investment Parnership, visited on march 3 2019]</ref>
== Енергетске залихе биљки ==
Most green plants use starch as their energy store.The extra glucose is changed into starch which is more complex than glucose(by plants). An exception is the family [[Asteraceae]] (asters, daisies and sunflowers), where starch is replaced by the [[fructan]] [[inulin]]. Inulin-like fructans are also present in grasses such as [[wheat]], in [[onion]]s and [[garlic]], [[bananas]], and [[asparagus]].<ref name="Vijn">{{cite journal |title=Fructan: more than a reserve carbohydrate? |first1=Irma |last1=Vijn | first2=Sjef |last2=Smeekens |journal=Plant Physiology |date=1999 |volume=120 |issue=2 |pages=351–360 |doi=10.1104/pp.120.2.351 |pmid=10364386 |doi-access=free|pmc=1539216 }}</ref>
In [[photosynthesis]], plants use light energy to produce [[glucose]] from [[carbon dioxide]]. The glucose is used to generate the chemical energy required for general [[metabolism]], to make organic compounds such as [[nucleic acids]], [[lipids]], [[proteins]] and structural polysaccharides such as [[cellulose]], or is stored in the form of starch granules, in [[amyloplast]]s. Toward the end of the growing season, starch accumulates in twigs of trees near the buds. [[Fruit]], [[seed]]s, [[rhizome]]s, and [[tuber]]s store starch to prepare for the next growing season.
Glucose is soluble in water, [[hydrophilic]], binds with water and then takes up much space and is [[osmosis|osmotically]] active; glucose in the form of starch, on the other hand, is not soluble, therefore osmotically inactive and can be stored much more compactly.
Glucose molecules are bound in starch by the easily [[hydrolysis|hydrolyzed]] [[glycosidic bond|alpha bonds]]. The same type of bond is found in the animal reserve polysaccharide [[glycogen]]. This is in contrast to many structural polysaccharides such as [[chitin]], cellulose and [[peptidoglycan]], which are bound by [[glycosidic bond|beta bonds]] and are much more resistant to hydrolysis.<ref>{{cite journal|last1=Zeeman|first1=Samuel C.|last2=Kossmann|first2=Jens|last3=Smith|first3=Alison M.|title=Starch: Its Metabolism, Evolution, and Biotechnological Modification in Plants|journal=Annual Review of Plant Biology|date=June 2, 2010|volume=61|issue=1|pages=209–234|doi=10.1146/annurev-arplant-042809-112301|pmid=20192737}}</ref>
=== Стварање скроба ===
Асимилациони (примарни) скроб настаје у фотосинтетском ткиву биљака ([[хлоропласт]]има). Примарни производ [[фотосинтеза|фотосинтезе]] је глукоза, али она се кондензује у нерастворљиви скроб. Током ноћи он се постепено разграђује и транспортује у друга [[Ткиво (биологија)|ткива]], а тамо се у [[амилопласти]]ма изграђују зрнца резервног скроба. Тај скроб је главни извор енергије у исхрани људи и домаћих животиња. Кртола [[кромпир]]а садржи око 30%, а [[пшеница|пшенична]] зрна и до 70 % скроба.<ref name="skrob"/>
=== Биосинтеза ===
Plants produce starch by first converting [[glucose 1-phosphate]] to [[Adenosine diphosphate|ADP]]-glucose using the enzyme [[glucose-1-phosphate adenylyltransferase]]. This step requires energy in the form of [[Adenosine triphosphate|ATP]]. The enzyme [[starch synthase]] then adds the ADP-glucose via a 1,4-alpha [[glycosidic bond]] to a growing chain of glucose residues, liberating [[Adenosine diphosphate|ADP]] and creating amylose. The ADP-glucose is almost certainly added to the non-reducing end of the amylose polymer, as the UDP-glucose is added to the non-reducing end of glycogen during glycogen synthesis.<ref>Nelson, D. (2013) Lehninger Principles of Biochemistry, 6th ed., W.H. Freeman and Company (p. 819)</ref>
[[Starch branching enzyme]] introduces 1,6-alpha glycosidic bonds between the amylose chains, creating the branched amylopectin. The starch debranching enzyme [[isoamylase]] removes some of these branches. Several [[isoform]]s of these enzymes exist, leading to a highly complex synthesis process.<ref>{{cite journal |doi=10.1021/bm000133c |title=The Biosynthesis of Starch Granules |year=2001 |last1=Smith |first1=Alison M. |journal=Biomacromolecules |volume=2 |issue=2 |pages=335–41 |pmid=11749190}}</ref>
Glycogen and amylopectin have similar structure, but the former has about one branch point per ten 1,4-alpha bonds, compared to about one branch point per thirty 1,4-alpha bonds in amylopectin.<ref>{{cite book |author1=Stryer, Lubert |author2=Berg, Jeremy Mark |author3=Tymoczko, John L. |title=Biochemistry |publisher=W.H. Freeman |location=San Francisco |year=2002 |isbn=978-0-7167-3051-4 |edition=5th |url=https://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=stryer |chapter=Section 11.2.2 |chapterurl=https://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=stryer.section.1517#1522}}</ref> Amylopectin is synthesized from ADP-glucose while mammals and fungi synthesize glycogen from [[Uridine diphosphate glucose|UDP-glucose]]; for most cases, bacteria synthesize glycogen from [http://www.genome.jp/dbget-bin/www_bget?C00498 ADP-glucose] (analogous to starch).<ref name=Ball2003>{{cite journal|last=Ball|first=Steven G.|author2=Matthew K Morell |title=FROM BACTERIAL GLYCOGEN TO STARCH: Understanding the Biogenesis of the Plant Starch Granule|journal=Annual Review of Plant Biology|year=2003|volume=54|issue=1|pages=207–233|doi=10.1146/annurev.arplant.54.031902.134927|pmid=14502990}}</ref>
In addition to starch synthesis in plants, starch can be synthesized from non-food starch mediated by an enzyme cocktail.<ref name="pnas.org">{{cite journal|last1=You|first1=C.|last2=Chen|first2=H.|last3=Myung|first3=S.|last4=Sathitsuksanoh|first4=N.|last5=Ma|first5=H.|last6=Zhang|first6=X.-Z.|last7=Li|first7=J.|last8=Zhang|first8=Y.- H. P.|title=Enzymatic transformation of nonfood biomass to starch|journal=Proceedings of the National Academy of Sciences|date=April 15, 2013|volume=110|issue=18|pages=7182–7187|doi=10.1073/pnas.1302420110|pmid=23589840|pmc=3645547}}</ref> In this cell-free biosystem, beta-1,4-glycosidic bond-linked cellulose is partially hydrolyzed to [[cellobiose]]. [[Cellobiose phosphorylase]] cleaves to glucose 1-phosphate and glucose; the other enzyme—potato [[alpha-glucan phosphorylase]] can add a glucose unit from glucose 1-phosphorylase to the non-reducing ends of starch. In it, phosphate is internally recycled. The other product, glucose, can be assimilated by a yeast. This cell-free bioprocessing does not need any costly chemical and energy input, can be conducted in aqueous solution, and does not have sugar losses.<ref>{{cite news|url=http://www.voanews.com/content/chemical-process-creates-food-source-from-plant-waste/1642851.html|title=Chemical Process Creates Food Source from Plant Waste|work=[[Voice of America]]|date=April 16, 2013|accessdate=January 27, 2017}}</ref><ref>{{cite journal | doi = 10.1002/ese3.2 | volume=1 | title=Next generation biorefineries will solve the food, biofuels, and environmental trilemma in the energy-food-water nexus | journal=Energy Science | pages=27–41| year=2013 | last1=Zhang | first1=Y.-H Percival }}</ref><ref>{{cite news|url=http://www.sciencemag.org/news/2013/04/could-wood-feed-world|title=Could Wood Feed the World?|first=Charles|last=Choi|work=[[Science (magazine)|Science]]|date=April 15, 2013|accessdate=January 27, 2016}}</ref>
== Састав ==
Скроб представља смесу два полисахарида, [[амилоза|амилозе]] и [[амилопектин]]а. То су полимери моносахарида -{D}--[[глукоза|глукозе]], а разликују се у начину везивања глукозних јединица. Амилоза има једноставнију грађу. Чини је неколико хиљада мономера повезаних α(1→4) гликозидном везом у дуге ланце. Амилопектин је разгранат и састоји се од главног и бочних ланаца. Главни ланац чине молекули глукозе повезани α(1→4) гликозидном везом, док се на сваких 20-30 остатака јавља бочни ланац (исте структуре) спојен α(1→6) гликозидном везом. Скроб садржи око 1/5 амилозе и 4/5 амилопектина.<ref name="skrob">{{Cite web |url=http://eskola.chem.pmf.hr/odgovori/odgovor.php3?sif=770 |title=Скроб |accessdate= 9. 2. 2008.|last= |first= |coauthors= |date= |work= |publisher=}}</ref>
[[Датотека:AdhesivesForHouseUse006.jpg|мини|200п|Скробни [[лепак]]]]
[[Датотека:Stärkemehl 800 fach Polfilter.jpg|мини|200п|Скробна зрнца]]
У хладној [[вода|води]], [[алкохол]]у и [[
Опна скробног зрнца је грађена од [[амилопектин]]а, а унутрашњост од [[амилоза|амилозе]]. Испитивањима је утврђено да зрнца имају семикристалну грађу, односно да поседују аморфна (неуређена) и кристална (уређена) подручја у којима су полимерни ланци повезани [[водоник]]овим везама. Кристаличност се повезује са амилопектинском компонентом скробне грануле, док се амилозна компонента повезује са неуређеним или аморфним подручјем.
Под деловањем [[киселина]] и [[ензим]]а скроб се може потпуно разгадити у [[глукоза|глукозу]], а међупродукти ове реакције су декстрини и малтоза.
== Употреба ==
Линија 56 ⟶ 105:
== Извори ==
{{reflist|
== Спољашње везе ==
{{Commonscat|Starch}}
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