Payvastahoi organiki ba hisobi miyona 20-30%-i massai hujay- rahoi organizmi zindaro tashkil medihand. Ba onho polimerhoi biologi – safedaho, kislotahoi nukleinat va angishtobho, vita- minho, amilokislotaho, inchunin, charbho va baze molekulahoi khurd – gormonho, pigmentho, ATF va gayra mansub meboshand. Dar namudhoi gunoguni hujayraho miqdori payvastahoi organiki yak khel nest. Dar hujayrahoi rustani angishtobhoi murakkab – poli- sakharidho bartari dorand; dar hayvonot safedaho va charbho zi- yodand. Bo vujudi in, dar har kadom namudi hujayra har yak guruhi moddahoi organiki amalhoi monandro ijro mekunand.
Polimerhoi biologi-safedaho
Dar bayni moddahoi organikii hujayra safedaho miqdoran bartari doshta, az ruyi ahamiyat joyi avvalro ishgol menamoyand. Dar hayvonot taqriban 50%-i massai khushki hujayraho ba safedaho rost meoyad. Dar organizmi odam 5 mln. kheli molekulahoi safedagi vomekhurand, ki na faqat bayni hamdigar, inchunin az safedahoi digar organizmho niz farq mekunand. Bo vujudi hamin qadar gu- noguni va murakkabii sokht safedaho hamagi az 20 aminokislotai gunogun tarkib yoftaand. Formulai umumii onho chunin ast:
K
I
N N -SN-SOON
Dar qismi chapi molekula guruhi amin N^ joygir shudaast, ki on khosiyati asosro zohir menamoyad; az tarafi rost – guruhi karboksil SOON – guruhi kislotagi joygir ast, ki baroi ta- momi kislotahoi organiki khos meboshad. Az in ru, fahmidan dushvor nest, ki aminokislotaho-payvastahoi amfoteri buda, ba khosiyathoi khimiyavii ham asos va ham kislota sohiband. In saba- bi bayni yakdigar tasiri mutaqobila namudani onho megardad. Molekulai aminokislotaho bo ham payvast shuda, bayni guruhi karboksili (SOON) va amini (I2K) band ba vujud meorand. CHu- nin bandro bandi kovalenti, vale dar in mavrid onro bandi peptidi menomand:
Payvast shudani du aminokislota dar yak molekula dipeptid, se aminokislota – tripeptid nomida meshavad. Payvastagii ibo- rat az 20 aminokislota va boqimondai az on beshtari aminokis- lotagiro polipeptid menomand.
Aminokislotaho sokhti umumii aniq dorand, lekin az hamdi- gar tanho bo sokhti radikal (K) farq mekunand, ki khele gunogun ast. Masalan, dar aminokislotai alanin radikal odi – SN meboshad, radikali aminokislotai sistein boshad, sulfur – SN2$N dorad; digar aminokislotaho radikalhoi beshtar murakkabro sohiband.
Rg *2
n2i – SN – SOON + N 21\1 – sn – soon
q k2
I I
—► n2i – SN – S – N – sn – soon + n 2o
II I
o n
Safedahoe, ki az organizmhoi zindai hayvonot, rustani va mikroorganizmho judo karda shudaand, az sadho va bazan az ha- zorho kombinatsiyai (bo hamdigar yakjoyashavii) 20 aminokislo- tai asosi iboratand. Tartibi paydarham (payiham) payvastsha- vii boqimondai aminokislotaho ba mavjudiyati miqdori ziyodi molekulai safedaho dar tabiati zinda imkoniyat dodaast; ha- mai onho az hamdigar farq mekunand. Paydarham joygirshavii aminokislotahoro dar zanjiri (silsilai) polipeptidi struktu- rai yakumini safeda menomand. Vale molekulai safeda dar namu- di zanjiri boqimondahoi aminokislotagi, ki payiham bayni yak- digar bo bandi peptidi payvast shudaand, hanuz qobiliyati ijro kardani funksiyai makhsusro nadorad. Baroi in, tashkili beshtarbalandi strukturai molekulai safeda zarur ast. Tavassuti ba vujud omadani bandhoi gidrogeni bayni boqimondai guruhhoi karboksil va aminoguruhhoi aminokislotahoi gunogun moleku- lai safeda namudi spirali sathash chindor (purchin) qabul me- namoyad (a struktura). In strukturai duyumini safeda meboshad. Ammo vay aksaran vaqt baroi qabuli faoliya- ti khosi biologi kofi nest.
Aksaran, tanho vaqte ki molekulai safeda strukturai seyu- min zohir menamoyad, dar on holat vazifai katalizator yo yagon vazifai digarro ijro karda metavonad.
Strukturai seyumini safeda ba tufayli tasiri mutaqobi- lai radikalho, qisman radikalhoi aminokislotai sistein, ki sulfur dorand, ba vujud meoyad. Atomhoi sulfuri du aminokis- lota, ki az yakdigar dar andak masofa dar zanjiri polipeptidi joygirand, payvast shuda, bo nom bandi disulfidi 8-8 ba vujud meorand. Ba tufayli chunin tasiri mutaqobila spirali safe- dagi pechutob khurda, shakli kura yo tubcha (kalobacha)-ro megirad. Qobiliyati joygir shudani spirali polipeptidi dar chunin kura strukturai seyumini safeda nomida meshavad. Bisyor safedaho, ki strukturai seyumin zohir menamoyand, vazifai biologii khudro dar hujayra ijro karda metavonand, lekin baroi ba amal ovar- dani baze funksiyahoi organizm ishtiroki safedahoi darajai tashkilyobiashon boz ham balandtar zarur ast. Hamin guna da- rajai balandi tashkilyobii sokhti molekulai safedaro struktu- rai chorumin menomand.
Strukturai chorumini safeda az muttahidshavii funksiona- lii yakchand (du, se va beshtar) molekulai safeda iborat ast, ki strukturai seyuminro zohir menamoyad. Misoli hamin guna safe- dai murakkab gemoglobin meboshad. Molekulai on az chor moleku- lai bayni yakdigar payvast iborat ast.
Az jumla, safedai dar bolo nomburda – gemoglobin payvasta- gii geterosiklii murakkab dorad, ki ba tarkibi on ohan dokhil ast.
Misoli digar gormoni gadudi zeri meda – insulin shuda me- tavonad, ki az du komponent (qismi tarkiby) iborat meboshad. Dar tarkibi strukturai chorumini baze safedaho, ba gayr az qismi safedagi, komponenthoi gunoguni gayri safedagi niz mavjudand.
Hosiyati safedaho. Safedaho monandi digar moddahoi gay- riorganiki va organiki yak qator khosiyathoi fizikiyu khimiyavi zohir menamoyand, ki az tashkilyobii strukturai onho barmeoyad. Pesh az hama, safedaho asosan molekulahoi dar ob halshavanda- and, binobar in faoliyati khudro tanho dar mahlulhoi obi zohir karda metavonand. Duyum, molekulahoi safedagi zaryadi kaloni sathi dorand, ki on yak qator tasiroti elektrokhimiyaviro mu- ayyan mekunad, masalan, faoliyati katalizii guzaronandagii membrana va digar amalho. Seyum, safedaho nisbat ba harorat noustuvorand, yane faoliyati khudro dar doirai haroratash kam zohir menamoyand.
Az tasiri harorati baland, inchunin, beob gardonidan, tagyiryobii rN va digar omilho strukturai safedaho vayron me- shavad. Dar ibtido strukturai az hama zaif – strukturai choru- min, bad seyumin va duyumin vayron khohand shud; vayronshavii strukturai yakumin boshad, dar sharoiti beshtar shadid ba amal meoyad. Strukturai khudro gum kardani molekulai safeda denatu- ratsiya nomida meshavad.
Agar tagyiroti sharoiti muhit ba vayronshavii strukturai yakumini molekula ovarda narasonad, pas dar vaqti barqaror namudani sharoiti mutadili muhit strukturai safeda va fa- oliyati funksionalii on purra ba vujud ovarda meshavad. CHunin ravand renaturatsiya nomida shudaast.
In khosiyati safeda dar tib baroi tayyor kardani baze do- ruho, masalan, antibiotikho, vaksinaho, khunoba, fermentho; dar sanoati khurokvori baroi hosil namudani konsentrathoi khuroki, ki dar holati khushk muddati daroz khosiyati gizoii khudro nigoh medorand, istifoda meshavad.
Funksiyai safedaho. Funksiyahoi safedaho dar hujayra niho- yat gunogun ast. YAke az muhimtarin funksiyahoi on – funksiyai plastiki (binokori) meboshad: safedaho dar kori ba vujud ovar- dani membrana va organoidhoi hujayra, inchunin strukturai gay- rihujayravi ishtirok menamoyand. Hususan, maqomi katalizii safedaho ahamiyati kalon dorad. Hamai katalizatorhoi biolo- gi-fermentho – moddahoi tabiatashon safedagi buda, surati reaksiyahoi khimiyaviro dar hujayraho to dahho va sadho hazor ma- rotiba metezonand.
Doir ba in funksiyai muhimmi safedaho tavaqquf namuda, onro qadre mufassal dida mebaroem. Istilohi «kataliz», ki dar khimiyai biologi nisbat ba sanoati khimiyavi kamtar duchor meoyad, aynan «kushodan», «ozod kardan»-ro mefahmonad. Moddahoe, ki ba katalizatorho mansuband, tabadduloti khimiyaviro tezonda, vale khudi onho sarf nameshavand, yane tarkibi katalizatorho pesh va bad az reaksiya tagyir nameyobad.
Mohiyati reaksiyai katalizi, qati nazar az miqdori ziyodi katalizatorhoi gunogun va navhoi reaksiyai khimiyavii dar onho ishtirokdoshta az on iborat ast, ki moddahoi avvala bo katali- zatorho payvastahoi mobayni hosil menamoyand. In payvastaho zud ba mahsuloti okhirin tabdil meyoband, vale katalizator dar namudi avvala barqaror megardad. Fermentho ham az jumlai chu- nin katalizatorho meboshand. Baroi onho niz hamai qonunhoi kataliz khos ast.
Ammo fermentho tabiati safedagi dorand, binobar in, onho khosiyati makhsus zohir menamoyand. Dar bayni fermentho va kata- lizatorhoi malumi khimiyai gayriorganiki, masalan, platina, oksidi vanadiy chi guna umumiyat va farq vujud dorad? Hamon yak katalizatori gayriorganikiro dar istehsoloti gunogun istifo- da burdan mumkin ast, vale ferment faqat yak reaksiya yo yak namudi reaksiyaro metezonad, yane on nisbat ba katalizatori gayriorga- niki makhsusiyati beshtar dorad.
F + S FS FP F + P
Rasmi 3.3. Tasiri mutaqobilai ferment (F) bo modda (S),
ki dar natija mahluli reaksiya (M) hosil meshavad.
YAke az khosiyathoi muhimmi fermentho dar organizm az hamin iborat ast. Malum ast, ki ba surati reaksiyahoi khimiyavi hama vaqt harorat tasir merasonad. Aksari reaksiyaho bo kataliza- torhoi gayriorganiki dar harorati nihoyat baland meguzarand.
Tasiri harorat ba faoliyati ferment:Hangomi baland kardani harorat, odatan, surati reaksiyahoi khimiyavi meafzoyad. Baroi reaksiyahoi fermentativi chunin afzo- ish dar harorati muvofiq mahdud ast .
- – ziyodshavi;
- – kamshavii surati reaksiya.
Minbad baland shudani harorat ba tagyirot dar struktu- rai ferment (nigared ba denaturatsiyai safedaho) ovarda mera- sonad, faoliyati on sust shuda, sipas qat megardad. Ammo baze fermenthoi mikroorganizmhoe, ki dar chashmahoi tabiii obashon garm yofta shudaand, na faqat ba harorati nazdik ba nuqtai ju- shishi ob tobovarand, balki hatto dar chunin sharoit faoliyati behad baland zohir karda metavonand.
Baroi aksariyati fermentho harorati muvofiq nazdiki 35- 400S meboshad. Reaksiyaho bo ishtiroki katalizatorhoi gayrior- ganiki, odatan, zeri fishori baland meguzarand, vale fermentho dar fishori mutadili atmosferi faoliyat mekunand. Farqi muhimmi fermentho nisbat ba digar katalizatorho dar on ast, ki surati reaksiyahoe, ki fermentho metezonand, to dahho, ha- zorho va bazan millionho marotiba az surati reaksiyahoe, ki dar ishtiroki katalizatorhoi gayriorganiki dastras megardad, balandtar meboshad.
Ba hama malum ast, ki peroksidi gidrogen (N2O2) hamchun moddai safedkunanda va dezinfeksiyavi ba kor burda meshavad. Vay be ishtiroki katalizator bisyor sust tajziya meshavad:
Tasiri suratnokii katalizatorho dar reaksiyahoi guno- gun ba energiyai aktivatsiya (faolnoki), yane hamon energiyae, ki rasondani on ba molekulai tasirkunanda zarur ast, vobastagi dorad. Mahz ba tufayli qimati kaloni energiyai aktivatsiya kogaz, chub, karasin va digar moddahoi suzanda dar harorati khona khud az khud darnamegirand. Agar onho dar muhiti oksigen garm karda sha- vand, on goh imkoniyati sukhtanashon ba amal meoyad. Har qadar ha- rorati muhiti atrof baland boshad, hamon qadar kamtar energiyai ilovagi sarf meshavad, to ki moddahoi suzanda alanga girand. Ka- talizatorhoi biologi – fermentho vazifai bo nom «garmkunanda- gi»-ro niz ijro mekunand. In imkoniyati bemamoniat ba reaksiya dokhil shudani bisyor molekulahoro tamin menamoyad.Dar ishtiroki katalizatori gayriorganiki (namakhoi ohan yo dioksidi mangan) reaksiyai tajziyai peroksidi gidrogen chand marotiba bosurattar meguzarad. Ammo katalaza (fermente, ki amalan dar hamai hujayraho mavjud ast) peroksidi gidrogenro bo surati nihoyat baland tajziya menamoyad: yak molekulai katala- za dar 1 daqiqa beshtar az 5 mln. molekulai peroksidi gidrogen- ro tajziya mekunad.
Funksiyai harakati organizmhoi zindaro safedahoi makhsusi kashishkhuranda tamin mekunand. In safedaho dar hamai navhoi harakat, ki ba onho organizm va hujayraho qobiliyat dorand, ishtirok menamoyand: larzishi muyak, mijgonak, junbishi qam- chinak dar sodatarinho, kashishkhurii mushakho dar hayvonoti serhujayra, harakati barg dar rustaniho va gayra.
Funksiyai naqliyotii safedaho dar payvast namudani ele- menthoi khimiyavi (masalan, oksigenro payvast kardani gemoglo- bin) yo moddahoi faoli biologi (gormonho), hamchunin, rasoni- dani onho ba boftahoi gunogun va uzvhoi badan ifoda meyobad. Safedahoi makhsusi naqliyoti KRN-ro, ki dar yadroi hujayra sintez meshavad, ba sitoplazma meguzaronand. Maqomi safedahoi naqli- yoti, khususan, dar membranahoi berunii hujayraho kalon ast: onho az muhit moddahoi gunogunro ba sitoplazma meguzaronand.
Hangomi ba organizm dokhil shudani safedahoi begona yo mikro- organizmho dar zarrahoi safedi khun (leykositho) safedahoi makh- sus (antitela) hosil meshavand. Onho moddahoi ba organizm begona (antigenho)-ro payvast menamoyand, ki dar natija komplekshoi beza- rar va bezahr «antigen-antitela» hosil meshavand. Onho minbad bo shaklhoi digari leykositho furu kashida shuda, hazm megardand (fagositoz) va in funksiyai muhofizatii safedaho meboshad.
Safedaho yake az manbahoi energiyai hujayra meboshand, yane funksiyai energetikiro niz ijro menamoyand. Dar vaqti to mahsu- loti okhirin purra tajziya shudani 1g safeda 17,6 kJ energiya kho- rij megardad, ammo dar organizm safedaho ba chunin sifat kam istifoda meshavand. Aminokislotaho, ki hangomi tajziyai mole- kulai safedaho ozod shudaand, dar reaksiyahoi mubodilai plastiki baroi bunyodi safedahoi nav ishtirok menamoyand.
Savolho baroi sanjish:
- Ba tarkibi hujayra kadom moddahoi organiki dokhil meshavand? Onhoro nombar kuned.
- Safedaho az kadom payvastahoi sodai organiki iboratand?
- Peptid chist? CHiro polipeptid menomand?
- Strukturai yakumini safeda chist?
- Strukturai duyumin, seyumin va chorumini safeda chi tavr ba vuchud meoyand? Onro sharh dihed.
- CHiro denaturatsiya va renaturatsiyai safeda menomand?
- SHumo kadom funksiyai safedahoro medoned? Misol ored.
Testho
- Payvastahoi organiki chand foizi huchayraro tashkil mekunand?
a) 20-30 %; b) 40-50 %; v) 10-15 %.
- Tarkibi safedaho az chi iborat ast?
a) glyukoza; b) aminokislota; v) glitserin.
- Sokhti safeda az chand aminokislotaho iborat ast?
a) 20; b) 25; v) 21.
- Aminokislotahoi safeda az hamdigar bo chi fark, mekunand?
a) bo guruhi karboksil; b) bo sokhti radikal; v) bo guruhi amini.
- Aminokislotaho dar zanchiri safeda chi khel bo ham payvast me- shavand.
a) peptidi; b) ioni; v) gidrogeni.
- Molekulai (zanchiri) safeda az chand sokhtor iborat ast?
a) 2- to; b) 3 – to; v) 4 – to.
- Dar sokhtori duyumin zanchiri tobkhurda kadom band dida meshavad? a) kovalenti; b) gidrogeni; v) sulfidi.
- Az kadom sokhtori safedagi faoliyati biologi sar meshavad.
a) yakumin; b) duyumin; v) seyumin.
- Kadome az in sokhtorhoi safedagi az hama noustuvortar ast?
a) yakum; b) duyum; v) chorum.
- Renaturatsiya chi mano dorad?
a) barqaror shudani sokhtori safedagi va vazifai on; b) vayron shu- dani sokhtori safeda; v) ichro nakardani vazifai khud.
- Safedaho dar huchayra yo organizm chand vazifaro ichro mekunand? a) du; b) chor; v) haft.
- Vazifai energetikii safedaho chi khel zohir meshavad?
a) hangomi tachziya shudani onho energiya chudo meshavad; b) safedaho hamchun sokhtmon; v) onho vazifai muhofizatiro ichro mekunand.
- Hangomi tachziya shudani 1g safeda chi qadar energiya khorich mesha- vad?
a) 10,5 kJ; b) 17,6 kJ; v) 38 kJ.