vishwal foto transduction

manushyarilum mattu kasherukkalilum kanninte rettinayile vadi koshangalilum koonn koshangalilum naadi aavegangal nalkunnathinu prakasham kandethunna vishwal sisttathinte censory transduction prakriyayaan vishwal foto transduction. ithu vishwal saikiline aasrayikkunnu, oopsinumaayi bandhikkappettirikkunna rettinayude oru thanmatra photoisomerisation vidheyamaakukayum photonine kandethunnathine soochippikkunna oru cascade aarambikkukayum, athinte photosensitive isomerilekku parokshamaayi punasthaapikkukayum cheiyunna biochemical prathikaranangalude oru kramam. fruit eechakal polulla chila akasherukkalil foto transduction samanamaaya prakriyakale aasrayichirikkunnu.
photoriseptarukal.
vadikal, konukal, foto sensitiivu ganglian cellukal (aii. pii. aarr. jii. sii) ennivayaanu kasherukkalude kaazhchayil ulppedunna photoriseptar cellukal. eee koshangalil oru kromophore (11-"sis"-rettinal, vitaamin eiii 1-nte aldehyde, prakasham agiranam cheiyunna bhagam) adangiyirikkunnu, athu oru sell membran proteinaaya oopsinumaayi bandhappettirikkunnu. kuranja prakasha nilaye kaikaaryam cheiyunna vadikal varnna kaazhchaykk madhyasthatha vahikkunnilla. maruvashathu, moonnu vyathyastha tharam konukalude aouttputtukal thaarathamyam cheiyunnathiloode oru chithratthinte niram coode cheyyaan konukalkku kazhiyum. oro koonn tharavum prakaashatthinte chila tharamgadairkhyangalodum nirangalodum mikacha reethiyil prathikarikkunnu, kaaranam oro tharatthinum alpam vyathyasthamaaya opsin undu. yathaakramam neelamulla tharamgadairkhyangal (chuvapp niram), idatharam tharamgadairkhyangal (pacha niram), hraswa tharamgadairkhyangal (neela niram) ennivayodu mikacha reethiyil prathikarikkunna ell-konukal, emm-konukal, ezz-konukal ennivayaanu moonnu tharam konukal. varnnadarsanam prapthamaakkunna moonnu ethirprakriya chaanalukal ulkkollunna trichrometic photopic kazhchayaanu manushyarkkullath.
drishyachakram.
vishwal oopsin, kromophore 11-"sis"-rettinal enniva adangiya retinylideen protein ennariyappedunna jii-protein cuppled resepterukaliloodeyaanu vishwal saikkil sambhavikkunnath. 11-"sis"-rettinal skiff bays vazhi oopsin resepterumaayi sahavarthithvathode bandhippichirikkunnu. ithu oru photonine agiranam cheyyumbol, 11-"sis"-rettinal ellah-trans-rettinalilekkum photoisomerisation vidheyamaakunnu, ithu oopsin gpcrinte roopeekaranathe maattunnu, ithu signal transduction kaaskedukalilekku nayikkunnu, ithu cyclic gmp-gated kaatteshan chaanal adaykkunnathinum photoriseptar sellinte hyperpolarisation kaaranamaakunnu. 
photoisomerisationethudurn, oopsin proteinil ninnu ool-trans-rettinal purathuvidukayum ool-trans-rettinolaayi kuraykkukayum cheiyunnu, ithu rettina pigment eppitheeliyathilekku "recharge" cheiyunnathinaayi sanjarikkunnu. ithu aadyam lesithin rettinol asil transferase (ell. aarr. tii) vazhi esterify cheyyukayum pinneedu isomerohydrolase aarr. pii. iii. 65 vazhi 11-"sis"-rettinolaayi parivartthanam cheyyukayum cheiyunnu. aarr. pii. iii. 65-nte isomerase pravartthanam kaanichittundu; ithu hydrolase aayi pravartthikkunnundo ennu urappilla. oduvil, photoriseptar sellinte puram bhaagathekku madangunnathinumumbu ithu 11-"sis"-retinalaayi ooksidais cheyyappedunnu, avide ithu veendum oru oopsinumaayi samyojippichu puthiyathum pravarthanakshamavumaaya vishwal pigment (retinylideen protein), athaayath photopsin allengil rhodopsin roopappeduthunnu.
transduction prakriya.
prakasha theevrathayodulla photoriseptarinte swabhaavam manasilakkaan, vyathyastha vaidyuthadhaarakalude punk manassilaakkendathu aavasyamaanu.
nongated keey +-selective chaanalukaliloode oru baahya pottasyam karant undu. eee baahya vaidyuthadhaara ekadesham −70 emvi (keey +-nte santhulithaavastha) yill photoriseptarine hyperpolarise cheiyunnu.
sii. jii. emm. pii-gated soodiyam chaanalukal vahikkunna oru aantharika soodiyam vaidyuthadhaarayum undu. eee "irunda vaidyuthadhaara" koshatthe ekadesham −40 emm. vii. aayi vidhruvalkkarikkunnu. mattu mikka neuronukalekkaalum ithu ganyamaayi kooduthal depolarised aanu.
Na +-k + pambukalude uyarnna saandrata photoriseptarine Na +, k + ennivayude sthiramaaya intra sellular saandrata nilanirthaan prapthamaakkunnu.
iruttil.
photoriseptar koshangal asaadhaaranamaaya koshangalaan, avaa uthejakangalude abhaavathilo scotopic avasthakaludeyo (iruttu) prathikaranamaayi depolarise cheiyunnu. photopic avasthakalil (prakasham), photoriseptarukal −60 emvi pottanshyalaayi hyperpolarise cheiyunnu.
iruttil, sii. jii. emm. pii alavu uyarnnathaan, koodaathe sii. jii. emm. pii-gated soodiyam chaanalukal thurannirikkukayum irunda karant ennu vilikkunna sthiramaaya aantharika vaidyuthadhaara anuvadikkukayum cheiyunnu. eee irunda vaidyuthadhaara koshatthe ekadesham −40 emm. vii. yill depolarise cheiyunnu, ithu neuronukalude uthejanathe thadayunna glutamate releasilake nayikkunnu.
scotopic avasthakalil kosha stharathinte depolarisation volteju gated kaalsyam chaanalukal thurakkunnu. kuranja +-nte vardhicha intra sellular saandrata glutamate adangiya vesikkilukal, oru neuro traansmittar, kosha stharavumayi layikkan kaaranamaakunnu, athinaal glutamate synaptic pilarppilekku vidunnu, ithu oru koshatthinte avasaanathinum mattoru neuroninte thudakkathinum edayilulla oru pradesamaanu. glutamate, saadhaaranayaayi uthejakamaanengilum, oru inhibittari neuro traansmittayi ivide pravartthikkunnu.
koonn pathayil, glutamate
velichathil.
churukkatthil "prakasham" sii. jii. emm. pii-gated soodiyam chaanalukal adaykkunnu, ithu Na +, Ca2 + ayonukalude ozhukk kuraykkunnu. Na + ayonukalude ozhukk thadayunnathu irunda vaidyuthadhaaraye phalapradamaayi "oof" cheiyunnu. eee irunda pravaham kuraykkunnathu photoriseptarine "hyperpolarise" cheyyaan kaaranamaakunnu, ithu glutamate release kuraykkunnu, ithu rettina njarambukalude "inhibition" kuraykkunnu, ithu eee njarambukalude "excitationilekku" nayikkunnu. foto transduction samayat eee kuranja kuranja + ozhukk thaazhe charcha cheythathupole foto transductionil ninnu nirjjeevamakkaanum veendedukkaanum prapthamaakkunnu.
foto transduction cascade nirjjeevamaakkuka.
velichathil, kuranja sii. jii. emm. pii levelukal naa +, kuranja + chaanalukal adaykkunnu, ithu intra sellular naa +, kuranja + enniva kuraykkunnu. 
veendedukkal samayat (irunda poruthappedutthal), kuranja kuranja + levelukal veendedukkaline prerippikkunnu (foto transduction cascade avasaanippikkunnu), inipparayunna reethiyil
kooduthal vishadamaayi
aarjiesinte (jii protein signalinginte regulatormaar) jidipes accelerating protein (gapp) traansdyoosinte alfa subunitumaayi samvadikkukayum athinte bandhita gtp gdpyilekku jalavishleshanam cheyyaan kaaranamavukayum angane phosphodeestaresinte pravartthanam nirthukayum cgmpyude gmp-yilekkulla parivartthanam thadayukayum cheiyunnu. foto transduction kaaskedinte (jii protein traansdyoosarinte nirjeevamaakkal) eee nirjeevamaakkal ghattam foto transduction kaaskedinte nirjeevamaakkalile nirakk parimithappedutthunna ghattamaanenn kandethi.
mattoru vidhathil paranjaal gwaanilettu saikles activating protein (gpap) oru kaalsyam binding proteinaan, koshatthile kaalsyatthinte alavu kurayumbol, gpap athinte bandhita kaalsyam ayonukalil ninnu verpedukayum gwaanilettu saiklesumaayi samvadikkukayum cheiyunnu. gwaanilettu saikles pinneedu jii. tii. piye sii. jii. emm. piyilekku parivartthanam cheiyunnathilekku neengukayum koshatthinte sii. jii. emm. pii levelukal niraykkukayum angane foto transduction samayat adacha soodiyam chaanalukal veendum thurakkukayum cheiyunnu.
oduvil, metarhodopsin II nirjjeevamaakkunnu. mattoru kaalsyam binding proteinaaya recoverine saadhaaranayaayi kaalsyam ullappol rhodopsin kinesumaayi bandhappettirikkunnu. foto transduction samayat kaalsyatthinte alavu kurayumbol, kaalsyam recoverinil ninnu verpiriyukayum rhodopsin kinez purathuvidukayum phosphorilettukal metarhodopsin II purathuvidukayum cheiyunnu, ithu transducinumaayulla bandham kuraykkunnu. avasaanamaayi, mattoru proteinaaya arrestin, phosphorylated metarhodopsin II neey bandhippikkukayum athu poornnamaayum nirjjeevamaakkukayum cheiyunnu. angane, oduvil, foto transduction nirjjeevamaakkukayum irunda vaidyuthadhaarayum glutamate release punasthaapikkukayum cheiyunnu. eee paathayilaanu metarhodopsin II phosphorylated cheyyukayum arast cheiyunnathilekku bandhikkukayum angane nirjjeevamaakkukayum cheiyunnathu, ithu dark adapteshante ezz 2 gadakathinu kaaranamaakumenn karuthappedunnu. ellah bleaching theevrathakalkkum irunda poruthappedutthalinte thudakkathil nilavilulla irunda poruthappedutthal pravartthanatthinte oru rekheeya vibhaagathe ezz 2 ghadakam prathinidheekarikkunnu.
akasherukkalil foto transduction.
pazha eecha polulla akasherukkalil foto transduction prakriya kasherukkalil ninnu vyathyasthamaan. paii (4,5) (4,5) saikkil foto transduction prakriyaykku adithara paakunnu. ivide, prakasham roopeekaranathe rhodopsinilekku prerippikkukayum athine mettaa-rhodopsinaayi parivartthanam cheyyukayum cheiyunnu. ithu jii-protein complexinte vighadanathinu sahayikkunnu. eee samuchayathinte alfa sub yoonit pii. ell. sii ensaimine (pii. ell. sii-beetta) sajeevamaakkunnu, ithu pii. pii. 2 neey dagilek jalavishleshanam cheiyunnu. eee jalavishleshanam tii. aarr. pii chaanalukal thurakkunnathilekkum kaalsyatthinte ozhukkilekkum nayikkunnu.

