Ukuphindaphinda kwamagciwane kumaseli omphathi
Ama-virus ayizinto ezincane kakhulu ezithelelanayo ezingakwazi ukusinda nokuzala ngokuzimela. Ngokungafani nama-bacteria noma isikhunta, anezinhlelo zawo ze-metabolic, ama-virus athembele cishe ngokuphelele kuma-host cells ukuze akhiqize izingxenye ezintsha. Ngakho-ke, inqubo yokuphindaphindana kwegciwane—inqubo lapho ama-virus ekopisha khona izinto zawo zofuzo futhi ahlanganise izinhlayiya ezintsha zegciwane—ihlala yenzeka ngaphakathi kweseli elibambayo. Ukuqonda izigaba zokuphindaphindana kwegciwane kubalulekile ku-biology, kwezokwelapha, nasempilweni yomphakathi, njengoba amasu amaningi okuvimbela nokwelapha enzelwe ukuvimbela esinye sezigaba ezibalulekile zalo mjikelezo.
Isakhiwo esiyisisekelo sama-virus kanye nokuthembela kwawo kumuntu ophethe
Ngokuvamile, amagciwane akhiwa ngezinto zofuzo (i-nucleic acid), okungaba yi-DNA noma i-RNA, evikelwe yi-protein coat ebizwa ngokuthi i-capsid. Amanye amagciwane anesendlalelo esengeziwe, i-envelope etholakala ku-host cell membrane, ehlonyiswe ngamaprotheni angaphezulu okunamathela kumaseli aqondiwe. Amagciwane awanawo ama-ribosome, ama-mitochondria, noma ama-enzyme aphelele e-metabolic. Ngenxa yalokho, ukuze azale kabusha, amagciwane kumele "antshontshe" imishini yeselula yomnikazi, okuhlanganisa ama-enzyme okuphindaphinda, izinhlelo zokuhumusha umbhalo, kanye nemithombo yamandla nezinto zokusetshenziswa.
Nakuba amagciwane ehluka kakhulu, umjikelezo wawo wokuphindaphinda ungaqondwa ngezigaba eziningana ezibalulekile: ukumuncwa (ukunamathela), ukungena (ukungena), ukukhishwa kwendwangu (ukukhululwa kwezinto zofuzo), ukuphindaphinda kanye nokwakheka kwamaprotheni, ukuhlanganiswa, kanye nokukhululwa. Ukwehluka kuncike ohlotsheni lwe-genome yegciwane (i-DNA/RNA, enentambo eyodwa/enentambo ephindwe kabili) kanye nokuba khona noma ukungabikho kwe-envelopu.
1. Ukumuncwa: ukunamathela kwegciwane esitokisini somsingathi
Isinyathelo sokuqala sokuphindaphinda ukumuncwa, inqubo lapho igciwane libona futhi linamathele khona ebusweni beseli eliphethe. Lokhu kunamathela akuhleliwe; amagciwane anamaprotheni akhethekile (njengokwanda kwamanye amagciwane ambozwe) abopha kuma-receptor athile kulwelwesi lweseli. Lawa ma-receptor angaba amaprotheni, ama-glycoprotein, noma ezinye izingxenye ebusweni beseli.
Ukucaciswa kokubopha kwe-virus-receptor kunquma i-tropism yegciwane, okungukuthi, ukuthi yiziphi izinhlobo zamaseli noma izicubu ezingatheleleka ngazo. Isibonelo, amagciwane athile angatheleleka kuphela ngamaseli omgudu wokuphefumula ngoba ama-receptor adingekayo atholakala ngobuningi kulolo zicubu. Lesi esinye sezizathu ezenza igciwane lingahlasela izitho ezithile futhi libangele izimpawu ezihlukile.
2. Ukungena: ukungena kwegciwane esitokisini
Ngemva kokunamathisela, igciwane kumele lingene esitokisini. Izindlela zokungena ziyahlukahluka kuye ngohlobo lwegciwane:
1. Ukuhlanganiswa kwe-membrane: kuma-virus amboziwe, i-virus envelope ingahlangana ne-host cell membrane, ukuze i-nucleocapsid ingene kwi-cytoplasm.
2. I-Endocytosis: amangqamuzana "agwinya" amagciwane ngokwakha ama-vesicle (ama-endosome). Amagciwane amaningi asebenzisa le ndlela, kokubili embozwe kanye nengamboziwe.
3. Ukujova izinto zofuzo: kuvame kakhulu kuma-bacteriophages (amagciwane ahlasela amagciwane). Igciwane linamathela odongeni lweseli lamagciwane bese lifaka i-nucleic acid yalo esitokisini.
Lesi sigaba sokungena ngokuvamile siwumgomo wokuthuthukiswa kwemithi, ngoba uma igciwane lingangeni, umjikelezo wokutheleleka awukwazi ukuqhubeka.
3. Ukuvula uboya: ukukhishwa kwezinto zofuzo ezibangelwa amagciwane
Uma selingaphakathi kweseli (kungaba ku-cytoplasm noma ku-endosome), igciwane liyakhishwa, okuwukukhululwa kwe-capsid yalo, okwenza izinto zalo zofuzo zitholakale ukuze ziphindaphindwe. Kwamanye amagciwane, izinguquko ku-pH ngaphakathi kwe-endosome zibangela ushintsho esimweni samaprotheni e-capsid, okubangela ukuba i-genome yegciwane ikhishwe. Kwamanye amagciwane, ama-enzyme eseli lomnikazi noma ama-enzyme egciwane uqobo asiza ekukhipheni i-capsid.
Ukuvula uboya kuyisinyathelo esibalulekile: uma i-genome ingakhishwa kahle, ukuphindaphinda ngeke kwenzeke. Ngaphezu kwalokho, kulesi sigaba, uhlelo lokuzivikela lweseli lungaqala ukubona ukuba khona kwegciwane, isibonelo ngezinzwa ze-RNA/DNA zangaphandle ezibangela impendulo yomzimba yokuzalwa.
4. Ukuphindaphindwa kwezakhi zofuzo kanye nokuhlanganiswa kwamaprotheni egciwane
Isigaba esilandelayo yingqikithi yokuphindaphinda: igciwane lisebenzisa iseli eliyibamba ukuphindaphinda i-genome yalo futhi likhiqize amaprotheni egciwane. Indlela esebenza ngayo ithonywa kakhulu uhlobo lwe-genome yegciwane.
a. Amagciwane e-DNA
Ama-virus amaningi e-DNA angena ku-nucleus yeseli lomnikazi ngokusebenzisa ama-enzyme okuphindaphinda kwe-DNA yeseli kanye nemishini yokubhala. I-DNA yegciwane iguqulwa ibe yi-mRNA yi-RNA polymerase yomnikazi, bese ihunyushwa ibe amaprotheni egciwane yi-ribosomes. Amanye ama-virus amakhulu e-DNA aphethe ama-enzyme awo, okwenza azimele kakhudlwana, kodwa asadinga izinsiza zamaseli.
b. Amagciwane e-RNA
Amagciwane e-RNA avame ukuphindaphinda ku-cytoplasm ngoba amangqamuzana abantu awanawo ama-enzyme angaphindaphinda i-RNA evela ku-RNA. Ngakho-ke, amagciwane e-RNA avame ukuthwala noma ukufaka ikhodi ye-enzyme i-RNA-dependent RNA polymerase (RdRp). Le enzyme yenza amakhophi e-RNA yegciwane futhi ikhiqize i-mRNA yokwenziwa kwamaprotheni.
Ama-virus e-RNA angaba:
– I-RNA enomuzwa omuhle (+) onentambo eyodwa: i-genome yayo ingasebenza ngqo njenge-mRNA futhi ihunyushwa ngokushesha.
– Umqondo ongemuhle (-) i-RNA enezintambo eyodwa: kumele kuqala ikopishwe ibe yi-RNA yomqondo omuhle ukuze ihunyushwe.
– I-RNA enezintambo ezimbili (dsRNA): idinga i-enzyme ekhethekile ukukhiqiza i-mRNA.
c. Igciwane le-Retrovirus
Ama-retrovirus ane-genome ye-RNA kodwa asebenzisa i-enzyme reverse transcriptase ukuguqula i-RNA ibe yi-DNA. Le DNA ibe isihlanganiswa ne-genome yeseli lomnikazi ngosizo lwe-enzyme integrase. Uma isihlanganisiwe, izinto zofuzo zegciwane zingaba "zithule" noma zisebenze, zikhiqize ama-mRNA amasha kanye nama-genome egciwane. Le ndlela yokuhlanganisa yenza kube nzima ukuqeda ukutheleleka kwe-retrovirus ngokuphelele.
Ngaphezu kokuphindaphinda kwe-genome, amaseli e-host aphinde aphoqeleke ukukhiqiza amaprotheni ahlelekile (i-capsid, amaprotheni e-envelope) kanye namaprotheni angewona ahlelekile (ama-enzyme okuphindaphinda, ama-protease, izici zokulawula). Amagciwane amaningi akhiqiza amaprotheni ngesimo sama-polyprotein amade, abese ehlukaniswa abe amayunithi asebenzayo yi-virus proteases.
5. Ukuhlanganiswa nokuvuthwa
Uma i-genome namaprotheni sekuqediwe, igciwane lingena esigabeni sokuhlangana. Amaprotheni e-Capsid ahlangana abe izakhiwo ezithile (isb., i-icosahedral noma i-helical) ngenkathi epakisha i-genome yegciwane. Le nqubo ingenzeka ku-cytoplasm noma ku-nucleus, kuye ngegciwane.
Amanye amagciwane adinga isigaba sokuvuthwa ukuze athelelane. Ukuvuthwa kungabandakanya ukuhlukana kwamaprotheni ngama-protease, izinguquko ekubunjweni kwe-capsid, noma ukwengezwa kwezingxenye ezengeziwe. Ngaphandle kokuvuthwa, izinhlayiya zegciwane ezivelayo zingase zibonakale ziphelele kodwa zingakwazi ukuthelela amaseli alandelayo.
6. Ukukhishwa kwamagciwane amasha avela kumaseli aphethwe yi-host
Isigaba sokugcina ukukhishwa kwama-virion (izinhlayiya zegciwane eziphelele) esitokisini ukuze athelele amanye amaseli. Izindlela zifaka:
1. I-Cell lysis: iseli liyaqhuma bese liyafa, likhipha ama-virion amaningi ngesikhathi esisodwa. Kuvamile kuma-virus angavalekile nakwezinye izifo eziyingozi ezilimaza izicubu.
2. Ukuhluma: Amagciwane amboziwe avela ngokuthatha ingxenye yolwelwesi lweseli eliphethe njengemvilophu. Le nqubo ayibulali njalo iseli ngokushesha, kodwa ingaphazamisa ukusebenza kweseli futhi ibangele ukuvuvukala.
3. I-Exocytosis: amanye amagciwane asebenzisa indlela yokukhipha iseli ukuze aphume ngama-vesicle.
Lo mjikelezo ungaba ngokushesha (amahora kuya ezinsukwini) noma uhambe kancane futhi ungahambisana nesigaba esicashile, kuye ngezici zegciwane kanye nempendulo yomnikazi.
Umthelela wokuphindaphindeka kwamagciwane kumaseli nasemzimbeni
Ukuphindaphindana kwamagciwane kungabangela umonakalo wamangqamuzana ngezindlela eziningana: ngokuqeda izinsiza zamangqamuzana, ukulimaza ulwelwesi kanye nama-organelle, ukuqala ukufa kwamangqamuzana okuhleliwe (i-apoptosis), noma ukubangela ukucindezeleka kwe-immunological. Ezingeni lezicubu, umonakalo kanye nokuvuvukala kuholela ezimpawini zesifo.
Ngakolunye uhlangothi, isimiso somzimba sokuzivikela sizama ukuyeka ukuphindaphindeka ngama-interferons, amaseli okubulala emvelo, ama-antibodies, namaseli e-T anobuthi. Kodwa-ke, ama-virus anezindlela ezahlukene zokugwema, njengokuvimbela ukusayinwa kwe-interferon, ukushintsha ngokushesha, noma ukufihla esigabeni esicashile.
Ukuphindaphinda njengento ehloselwe ukwelashwa nokuvimbela
Imithi eminingi yokulwa namagciwane yenzelwe ukuqondisa izigaba ezithile, isibonelo:
– kuvimbela ukungena kwamagciwane,
– kuvimbela ama-enzyme okuphindaphinda (i-RdRp, i-reverse transcriptase),
- kuvimbela ama-protease ukuvimbela ukuvuthwa,
– kuvimbela ukukhishwa kwama-virion.
Imijovo isebenza ngokuyinhloko ngokulungiselela amasosha omzimba ukuze aqaphele ngokushesha igciwane ngaphambi kokuba liphinde liphindaphindeke ngendlela engalawuleki. Ngama-antibodies anciphisa ukwakheka kwamangqamuzana e-T kanye nokusabela okunamandla kwamaseli e-T, igciwane lingavinjelwa ekunamatheleni, ekungeneni, noma ekusakazekeni kabanzi.
I-Penutup
Ukuphindaphinda kwamagciwane kumaseli aphethe kuyinqubo ecophelelayo, enezinyathelo eziningi, kusukela ekunamatheleni kuya ekukhishweni kwama-virion amasha. Nakuba amagciwane ebonakala "elula," ikhono lawo lokusebenzisa izinhlelo zamaseli liwenza aphumelele kakhulu ekusakazeni nasekubangeleni izifo. Ukuqonda lezi zindlela zokuphindaphinda akubalulekile nje kuphela ngokwezemfundo kodwa futhi kubalulekile ekuthuthukisweni kwemithi yokulwa namagciwane, imigomo, namasu okulawula ukuqubuka kwamagciwane. Ngokugxila emaphuzu abalulekile emjikelezweni wokuphila kwamagciwane, abantu banganciphisa umthelela wokutheleleka futhi bathuthukise ukuqina kwempilo yomphakathi.
