Ciclo futile

Questa voce è orfanaQuesta voce è orfana, ovvero priva di collegamenti in entrata da altre voci.
Inseriscine almeno uno pertinente e utile e rimuovi l'avviso. Segui i suggerimenti del progetto di riferimento.

Un ciclo futile, noto anche come ciclo del substrato, si verifica quando due vie metaboliche avvengono simultaneamente in direzioni opposte senza alcun effetto complessivo se non quello di dissipare energia sotto forma di calore .[1]

Ad esempio, se la glicolisi e la gluconeogenesi dovessero essere attive contemporaneamente, il glucosio verrebbe convertito in piruvato dalla glicolisi e quindi riconvertito in glucosio dalla gluconeogenesi, con un consumo complessivo di ATP .[2] Considerando l'insieme dei processi, si avrebbe quindi un ciclo futile.

Il motivo per cui cicli metabolici di tale natura stati chiamati "futili" è il fatto che, in prima analisi, si pensava che questi cicli operassero senza alcuna utilità netta per l'organismo. Dopo ulteriori studi si è però giunti alla conclusione che i cicli futili sono molto importanti per regolare le concentrazioni dei metaboliti e quindi rivestono una importante funzione nella regolazione metabolica.[3] Un ciclo futile agirebbe infatti da sistema regolatorio, oscillando tra diversi stati metabolici e costituendo una sorta di sensore rispetto ai piccoli cambiamenti che possono riguardare l'attività di uno qualsiasi degli enzimi coinvolti.[4] Inoltre, dal momento che i cicli futili dissipano energia sotto forma di calore, possono essere utilizzato per mantenere l'omeostasi termica, ad esempio nel tessuto adiposo bruno di giovani mammiferi, o per generare calore rapidamente, ad esempio nei muscoli del volo degli insetti e negli animali in letargo durante il periodo di risveglio dal torpore.

Esempio di ciclo futile: glicolisi e gluconeogenesi

Lo svolgimento simultaneo della glicolisi e della gluconeogenesi è un esempio di ciclo futile, rappresentato complessivamente dalla seguente equazione: Più nello specifico, durante la glicolisi, il fruttosio 6-fosfato viene convertito in fruttosio 1,6-bisfosfato in una reazione catalizzata dall'enzima 6-fosfofruttochinasi (PFK-1), con tale bilancio: ATP + fruttosio-6-fosfato → Fruttosio-1,6-bisfosfato + ADP Tuttavia, durante la gluconeogenesi avviene la reazione inversa, catalizzata dalla fruttosio 1,6-bisfosfatasi (FBPasi 1), con tale bilancio: Fruttosio 1,6-bisfosfato + H 2 O → fruttosio 6-fosfato + P i L'insieme dei due processi può essere riassunto da tale reazione generale, in cui compare il termine "calore" a indicare l'energia dissipata: ATP + H 2 O → ADP + P i + Calore Si tratta di un processo di idrolisi dell'ATP senza che venga svolto alcun lavoro metabolico utile. Se all'interno della cellula queste due reazioni dovessero procedere simultaneamente ad una velocità elevata, una grande quantità di energia chimica verrebbe dissipata sotto forma di calore. Processi di questo tipo, che possono apparire come inutili sprechi energetici sono stati quindi chiamato cicli futili.[5]

Note

  1. ^ Schwender J, Ohlrogge J, Shachar-Hill Y, Understanding flux in plant metabolic networks, in Curr Opin Plant Biol, vol. 7, n. 3, 2004, pp. 309–17, DOI:10.1016/j.pbi.2004.03.016, PMID 15134752.
  2. ^ Boiteux A, Hess B, Design of glycolysis, in Philos Trans R Soc Lond B Biol Sci, vol. 293, n. 1063, 1981, pp. 5–22, DOI:10.1098/rstb.1981.0056, PMID 6115423.
  3. ^ Garrett, Reginald H., Biochemistry, Grisham, Charles M., Sixthª ed., Boston, MA, 11 febbraio 2016, pp. 767, ISBN 9781305577206, OCLC 914290655.
  4. ^ Samoilov M, Plyasunov S, Arkin A, Stochastic amplification and signaling in enzymatic futile cycles through noise-induced bistability with oscillations, in Proc Natl Acad Sci USA, vol. 102, n. 7, 2005, pp. 2310–5, DOI:10.1073/pnas.0406841102, PMID 15701703.
  5. ^ Nelson, D. L., Lehninger, A. L., & Cox, M. M. (2008). Lehninger principles of biochemistry (5th ed., pp. 582-583). New York: W.H. Freeman.

Read other articles:

العلاقات البريطانية البنمية

العلاقات البريطانية البنمية المملكة المتحدة بنما   المملكة المتحدة   بنما تعديل مصدري - تعديل   العلاقات البريطانية البنمية هي العلاقات الثنائية التي تجمع بين المملكة المتحدة وبنما.[1][2][3][4][5] مقارنة بين البلدين هذه مقارنة عامة ومرجعية للد...

 

Jacob Crowninshield

American politician (1770–1808) Jacob CrowninshieldMember of the U.S. House of Representativesfrom Massachusetts's 2nd districtIn officeMarch 4, 1803 – April 15, 1808Preceded byWilliam ShepardSucceeded byJoseph StoryMember of the Massachusetts SenateIn office1801 Personal detailsBorn(1770-03-31)March 31, 1770Salem, Province of Massachusetts Bay, British AmericaDiedApril 15, 1808(1808-04-15) (aged 38)Washington, D.C., U.S.Resting placeHarmony Grove Cemetery, Salem...

 

趙家驤

追晉陸軍二級上將趙家驤將軍个人资料出生1910年 大清河南省衛輝府汲縣逝世1958年8月23日(1958歲—08—23)（47—48歲） † 中華民國福建省金門縣国籍 中華民國政党 中國國民黨获奖 青天白日勳章（追贈）军事背景效忠 中華民國服役 國民革命軍 中華民國陸軍服役时间1924年－1958年军衔 二級上將 （追晉）部队四十七師指挥東北剿匪總司令部參謀長陸軍�...

Imperial Prize of the Japan Academy

Japanese award For other uses, see Japan Academy Prize (disambiguation). the Award Ceremony for the Imperial Prize and Japan Academy Prize (at the Building of Japan Academy on June 17, 2019) The Imperial Prize of the Japan Academy (恩賜賞, onshishō) is a prestigious honor conferred to two of the recipients of the Japan Academy Prize. Overviews It is awarded in two categories: humanities and natural sciences.[1] The Emperor and Empress visit the awarding ceremony and present a vase...

 

Nauka (ISS module)

Module of the International Space Station This article is about the ISS component. For the academic publisher, see Nauka (publisher). NaukaForward view of Nauka and attached to it from the Cupola, during the Russian VKD-51 spacewalk in January 2022.Module statisticsCOSPAR ID2021-066APart ofInternational Space StationLaunch date21 July 2021, 14:58:25 UTC (2 years, 9 months and 4 days ago)Launch vehicleProton-MDocked29 July 2021, 13:29:01 UTCMass 20,357 kg (44,880&...

 

2023 U.S. Women's Open

Golf tournament2023 U.S. Women's OpenTournament informationDatesJuly 6–9, 2023LocationPebble Beach, California, U.S.36°34′05″N 121°57′00″W / 36.568°N 121.950°W / 36.568; -121.950Course(s)Pebble Beach Golf LinksOrganized byUSGATour(s)LPGA TourStatisticsPar72[1]Length6,509 yards (5,952 m)[2]Field156 players, 74 after cutCut150 (+6)Prize fund$11,000,000Winner's share$2,000,000Champion Allisen Corpuz279 (−9)Location mapPebble BeachGolf...

The Connecticut Mirror

The Connecticut MirrorTypeNonprofitFormatWebOwner(s)nonprofitPublisherBruce Putterman[1]Editor-in-chiefElizabeth HamiltonFounded2009Political alignmentNonpartisanHeadquarters1049 Asylum AvenueHartford, Connecticut[2]Websitectmirror.org The Connecticut Mirror (also known as CT Mirror) is a nonprofit, non-partisan, online-only news organization covering public policy, government, and politics in Connecticut. Based in Hartford, Connecticut, CT Mirror was founded in 2009 and firs...

 

دائرة الدريوش

خريطة لدوائر إقليم الناظور(صورة قديمة) دائرة الدريوش تقسيم إداري البلد المغرب  التقسيم الأعلى إقليم الدريوش  السكان التعداد السكاني 61068 (2004)[1]    • عدد الأسر 10369 (2004)[1]  تعديل مصدري - تعديل   دائرة الدريوش هي إحدى الدائرتين المكونة لإقليم الدريوش وتتموق...

 

1892 United States presidential election in Georgia

Election in Georgia Main article: 1892 United States presidential election 1892 United States presidential election in Georgia ← 1888 November 8, 1892 (1892-11-08) 1896 →   Nominee Grover Cleveland Benjamin Harrison James B. Weaver Party Democratic Republican Populist Home state New York Indiana Iowa Running mate Adlai Stevenson I Whitelaw Reid James G. Field Electoral vote 13 0 0 Popular vote 129,446 48,408 41,939 Percentage 58.01...

Appalachia

Geographic region in the Appalachian Mountains of the Eastern United States This article is about the region in the United States. For other uses, see Appalachia (disambiguation). Region in United States of AmericaAppalachiaRegionLeft–right from top: Pittsburgh skyline New River Gorge Bridge campus of Appalachian State University Smoky Mountains Roanoke skyline mountains of North Georgia view from the Appalachian Trail Red and dark red counties form the Appalachian Regional Commission; dark...

 

Croatian People's Party – Liberal Democrats

Croatian liberal political party Croatian People's Party redirects here. For historic parties, see People's Party (Kingdom of Croatia) and Croatian People's Party (1919). Croatian People's Party – Liberal Democrats Hrvatska narodna stranka – Liberalni demokratiAbbreviationHNS-LD, HNSPresidentMirko Korotaj[1]FounderSavka Dabčević-KučarFounded13 October 1990 (1990-10-13)HeadquartersZagrebMembership (2022)31,793[2]IdeologySocial liberalism[3]Pro-Euro...

 

Liberty Bell

Symbol of American independence and liberty For other uses, see Liberty Bell (disambiguation). Liberty BellThe Liberty Bell outside Independence Hall in Philadelphia in April 2017Interactive map pinpointing the bell's location39°56′58″N 75°9′1″W / 39.94944°N 75.15028°W / 39.94944; -75.15028LocationLiberty Bell CenterPhiladelphia, Pennsylvania, U.S.DesignerWhitechapel Bell FoundryTypeTower bellMaterial70% Copper, 20% Tin, 10% other metalsWidth3.82 ft (1...

Hizen Province

Former province of Japan For the former Russian battle ship operated as Hizen by the Imperial Japanese Navy from 1908 to 1922, see Russian battleship Retvizan. Map of Japanese provinces (1868) with Hizen Province highlighted Hizen Kokuchō Site in Saga Hizen Kokubun-ji Site in Saga Hizen Province (肥前国, Hizen no kuni) was an old province of Japan in the area of the Saga and Nagasaki prefectures.[1] It was sometimes called Hishū (肥州), with Higo Province. Hizen bordered on the...

 

Murchison Widefield Array

Cet article est une ébauche concernant l’astronomie. Vous pouvez partager vos connaissances en l’améliorant (comment ?) selon les recommandations des projets correspondants. Murchison Widefield ArrayUne des très nombreuses dalles formant le MWA.PrésentationType Radio-interféromètre (d)Observatoire Observatoire de radioastronomie de MurchisonConstruction 2007-2012Site web www.mwatelescope.orgDonnées techniquesDiamètre 3 000 mLongueur d'onde 3,8 G nm et 1 000 M nmGé...

 

Custard pie

Pastry container with a sweet egg mixture This article is about the dessert. For the Led Zeppelin song, see Custard Pie. Not to be confused with Custard tart. Custard pieA version of coconut cream pieTypePieMain ingredientsPie shell, custard Pear custard pie Look up custard pie  or custard in Wiktionary, the free dictionary. A custard pie is any type of uncooked custard mixture placed in an uncooked or partially cooked crust and baked together.[1] In North America, custard pie co...

Windows Server

Microsoft > Microsoft Windows > Windows NT系 > Windows Server Windows Server 開発者 マイクロソフト初版 2003年4月24日 (21年前) (2003-04-24)最新安定版 Windows Server 2022 (10.0.20348.2527) / 2023年6月11日 (12か月前) (2023-06-11)[1]最新開発版 Windows Server vNext (10.0.26236) / 2024年6月12日 (17日前) (2024-06-12)[2]アップデート方式 Windows Update, Windows Server Update Services, SCCM...

 

Stasiun Shimbashi

35°39′59″N 139°45′31″E / 35.666301°N 139.758679°E / 35.666301; 139.758679 Stasiun Shimbashi新橋駅Pintu keluar Stasiun JR ShimbashiLokasiPrefekturTokyo(Lihat stasiun lainnya di Tokyo)Distrik kotaMinatoSejarahDibuka1909Nama sebelumnyaKarasumori StationNama sekarang digunakan sejak1914Layanan kereta apiOperatorJR EastTokyo MetroToei SubwayJalurJalur Keihin-TōhokuJalur Utama TōkaidōJalur YamanoteJalur YokosukaJalur Tokyo Metro GinzaJalur Toei AsakusaYurik...

 

Willem-Alexander av Nederländerna

Willem-Alexander Regeringstid 30 april 2013–(11 år och 80 dagar) Företrädare Beatrix av Nederländerna Gemål Máxima Zorreguieta (vigda 2 februari 2002) Barn Catharina-Amalia (född 2003)Alexia (född 2005)Ariane (född 2007) Personnamn Willem-Alexander Claus George Ferdinand Postumt namn Willem-Alexander Claus George Ferdinand Ätt Huset Nassau-Oranien Far Claus von Amsberg Mor Beatrix av Nederländerna Född 27 april 1967 (57 år)Utrecht, Nederländerna Namnteckning Heraldiskt v...

Harald Heide-Steen Jr.

Harald Heide-Steen Jr.Heide-Steen Jr. pada 1965LahirHarald Heide-Steen Jr.(1939-08-18)18 Agustus 1939Oslo, NorwegiaMeninggal3 Juli 2008(2008-07-03) (umur 68)Oslo, NorwegiaPekerjaanPemeran, pelawak, penyanyi jazzTahun aktif1959–2008Suami/istriGullen ØyehaugSitus webHeide-Steen Jr. at Kjentfolk.no Penghargaan(2007) Oslo City Culture Award (en) (1991) Leif Justers Award (en) (1984) Leonard Statuette (en) (1978) Spellemannprisen for best spoken word recording (en) Kongens forteneste...

 

Pancha Kanya

Village development committee in Narayani Zone, NepalPancha Kanya पञ्चकन्याVillage development committeeCountry   NepalZoneNarayani ZoneDistrictChitwan DistrictPopulation (1991) • Total10,281Time zoneUTC+5:45 (Nepal Time) Pancha Kanya is a village development committee in Chitwan District in the Narayani Zone of southern Nepal. At the time of the 1991 Nepal census it had a population of 10,281 people living in 1,996 individual households.[...