LI NI U

T khi hc thuyt t bo ra i (1838 - 1839), sinh hc chuyn sang mt giai on mi. T bo hc tr thnh mn khoa hc c s cho cc ngnh sinh hc khc. Nhng thnh tu v t bo hc gp phn y mnh s pht trin cc ngnh sinh hc.

L mn khoa hc c s, T bo hc tr thnh mn hc bt buc trong chng trnh o to khoa Sinh cc trng i hc S phm, i hc Khoa hc t nhin cng nh mt s trng trong khi Nng - Lm - Ng - Y.

phc v cho vic hc tp, nghin cu v t bo hc ca cn b, sinh vin, chng ti tin hnh bin son gio trnh T bo hc ny.

hon thnh gio trnh ny, chng ti nhn c s gp qu bu ca nhiu ng nghip, c bit l PGS. TS. Nguyn Nh Hin - i hc Quc gia H Ni. Chng ti chn thnh cm n nhng kin ng gp qu bu .

V cn hn ch v ngun t liu cng nh trnh nn gio trnh khng trnh khi nhng sai st. Chng ti rt mong nhn c kin ng gp ln ti bn sau gio trnh c hon thin hn. CC TC GI

M u

1. i tng v nhim v ca mn T bo hc T bo hc l mt mn khoa hc nghin cu t bo. T bo l n v t chc c s

ca vt cht sng v hnh thi, sinh l sinh ha v di truyn. T bo tn ti tt c cc mc ca t chc sng c th vi sinh vt, thc vt v

ng vt. V vy, vi sinh vt, ng vt v thc vt u l i tng nghin cu ca t bo hc.

Cu trc ca siu vi khun (virus) khng c nhng c im chung vi cu trc t bo, chng thiu h thng enzyme nn thiu s trao i cht ring ca mnh, do siu vi khun khng thuc phm vi v i tng nghin cu ca t bo hc.

Cc c th vi sinh vt c th xem l cc c th c t chc mc t bo m nhn ca chng h phn tn. Chng l i tng nghin cu ca t bo hc.

Cc c th n bo nh nguyn sinh ng vt l nhng c th c cu trc ch gm mt t bo. Mc du c th n bo c tnh a dng, nhng chng vn gi cu trc chung ca t bo. Nh vy, c th n bo va l t bo va l c th ton vn.

Trong c th a bo c nhiu loi t bo phn ho khc nhau trn c s phn ha chc nng. V d: t bo bch cu vn gi nguyn tnh cht nguyn thu, tri li vi nhng t bo phn ho cao nh t bo thn kinh. Tuy c phn ha cao, nhng t bo trong c th a bo vn gi c nhng nt c trng ca mt t bo ring r. Nh vy, t bo ca c th a bo khng ch l mt thnh phn ca c th ton vn m cn l mt n v sng ton vn.

Nghin cu tt c cc c tnh cu trc, di truyn cc qu trnh sinh l, sinh ho, ngun gc v tin ha ca t bo tt c cc dng tn ti l i tng ca mn t bo hc i cng.

Nhng, trc kia, t bo hc ch nghin cu b hp trong lnh vc hnh thi hc, mt s qu trnh sinh l, cn qu trnh sinh ho, l sinh, di truyn t bo cha c nghin cu. Mi n nhng nm 30 ca th k XX, do s xm nhp ca cc mn khoa hc khc nh ton, l, ha vo sinh hc v do ng dng cc phng tin nghin cu mi trong sinh hc nh k thut hin vi in t, ha t bo, li tm siu tc, nguyn t, nh du, phn tch cu trc bng tia Rnghen... th trong t bo hc c mt cuc cch mng ln, i su vo nghin cu cc hin tng l sinh, cc qu trnh sinh ho - nghin cu mc siu hin vi v c mc phn t, v t c nhng thnh tu to ln, t mn t bo hc vo v tr mi nhn ca nn khoa hc sinh hc hin i.

Nhim v ca mn t bo hc hin nay l nghin cu v gii quyt 3 vn ln: vn tin ha; vn t iu khin; vn t sinh sn ca t bo.

* Vn tin ho ca t bo gm:

- Lm sng t con ng xut hin phc h t chc t bo trong qu trnh hnh thnh s sng.

- Nghin cu cc nh lut tin ha ca t bo cc dng tn ti (l vn chng loi pht sinh ca t bo).

- Nghin cu cc vn c lin quan n qu trnh c th pht sinh ca t bo c th n bo v c th a bo.

* Vn t iu khin bao gm:

- Nghin cu cc qu trnh bo m cho s sng ca t bo. - Nghin cu c ch, qu trnh a n trng thi bt bnh thng ca t bo. - nh tnh, thch nghi ca t bo vi mi trng sng. - Nghin cu cc c ch iu ha cc qu trnh ni bo theo khng gian v thi

gian. - Nghin cu phng thc tn ti ca chc phn v quan h tng h gia cc t bo

trong c th a bo di h thng iu khin chung ca c th.

* Vn sinh sn bao gm:

- Nghin cu cc qu trnh sinh sn v sinh trng ca t bo v cc cu trc ca t bo.

- Lm sng t c ch tng hp protein trong t bo, c ch, chc nng di truyn ca t bo: tch thng tin di truyn, chuyn thng tin di truyn cho th h cc t bo con.

- T bo c xem l n v sng c bn c v cu trc, chc phn cng nh di truyn ca tt c cc dng tn ti ca cc t chc sng, do t bo hc c xem l trung tm ca h thng khoa hc sinh hc. Chnh y cng l ni gp g ca cc kin thc ton, l, ha. Thnh tu ca t bo hc l c s gii quyt cc vn c bn nh: ngun gc s sng, vn sinh tng hp protein, vn di truyn hc... cc vn trong y hc v nng nghip... ng thi cng l c s vng chc cho khoa hc trit hc duy vt macxit.

2. S lc lch s mn T bo hc Danh t t bo bt ngun t ch Latinh "Cela" c ngha l xoang rng, c

Robert Hooke dng ln u tin vo nm 1665 khi ng miu t cu trc ca nt bn di knh hin vi phng i 30 ln do ng ch to.

Khong 10 nm sau (1674), Leewenhook vi knh hin vi phng i 270 ln, ln u tin quan st thy cc t bo t do, cc cu trc cha bn trong t bo v pht hin ra nhn ca t bo hng cu. Tuy nhin, thi by gi ngi ta cha c khi nim r rng v cu trc cha bn trong t bo. Nhng hiu bit u tin nh vy ko di 100 nm. Mi n th k XIX, nh s hon thin dn ca knh hin vi m c nhiu cng trnh nghin cu t bo ra i. T , ngi ta khm ph ra hng lot cc cu trc quan trng trong t bo.

ng ch hn c l cng trnh nghin cu v tng kt ca nh thc vt hc Schleiden (1838) v nh ng vt hc Schwann (1839). Trn c s cng trnh nghin cu ca mnh v da vo kt qu ca nhiu cng trnh trc , hai ng tng kt nng ln thnh l lun. V hc thuyt t bo ra i. Hc thuyt t bo xc nhn rng: Tt c sinh vt t ng vt, thc vt v c c th n bo u c cu to gm cc t bo v cc

sn phm ca t bo. Hc thuyt t bo l mt trong nhng tng kt v i v sinh hc. Hc thuyt t bo ra i c nh hng ln n tt c cc hng nghin cu sinh hc. Sinh hc v t bo hc bt u pht trin mnh m t y. Tuy nhin, trong sut th k XIX, t bo hc ch tp trung nghin cu v cu trc v hin tng sinh sn ca t bo v hnh thi... l thi k nghin cu t bo c tnh cht c in.

Trong nhng nm ca th k XX, t bo hc pht trin rt mnh, nhanh chng t c nhiu thnh tu ln. Thnh cng nh vo hai nguyn nhn sau:

- S tin b ca k thut, ca phng php nghin cu, trc ht l k thut hin vi in t v phn tch cu trc bng tia Rnghen.

- S phi hp cht ch vi cc mn khoa hc khc nh di truyn, sinh l, sinh ho v l sinh.

Nh vy m cc nh t bo hc i su nghin cu cu trc siu hin vi, cu trc phn t ca t bo v cc qu trnh sinh l, sinh ho, l sinh trong t bo hc.

Sau y cp n mt s thnh tu t c Nhng thnh tu khoa hc ca ngnh sinh l t bo: T ch nghin cu t bo trn mu vt c x l v nhum mu th k XIX,

bc sang th k XX, cc nh sinh l hc tp trung nghin cu cc t bo sng. T ch ch nghin cu cc dng vn ng ca t bo nh c ng amip, t c ng ca tim mao..., ngi ta sng to v p dng cc phng php nghin cu mi nh phng php nui cy t bo ca Harison (1909) v ca Caren (1912). Nh phng php ny m cc nh nghin cu c th tch c cc dng t bo thun v nghin cu c cu trc v chc nng ca t bo sng mt cch tt nht.

Nm 1911, Caren p dng phng php phu thut vo t bo. Nh , ngi ta nghin cu thnh cng hng lot vn nh: xc nh nht, ngha ca pH, qu trnh oxy ha kh, quan h gia nhn v t bo cht...

nghin cu qu trnh sinh l v tnh cht l ha, cc nh t bo hc tp trung nghin cu bn cht ca mng t bo lm m hnh mng; nghin cu s vn chuyn v c ch vn chuyn cc cht qua mng; nghin cu s cm ng v co rt ca t bo, cng cc hot ng khc ca t bo. Ngi ta thnh cng trong nghin cu in sinh hc ca t bo v c nhng kt qu em ra p dng phc v sc kho con ngi. Gn y, ngi ta ch n qu trnh t iu khin v t iu ha trong t bo v thu c nhng kt qu ng k.

Nhng nghin cu ca ha t bo: Cng trnh nghin cu c ngha u tin ca ha t bo l pht hin v tch c

acid nucleic t t bo bch cu, t tinh trng, t hng cu chim ca Mise (1869) v ca Cotsen (1891). V sau cng trnh ca Watson v Crick th vai tr quan trng ca acid i vi sinh tng hp protein, di truyn t bo mi c lm sng t. Ngi ta khm ph ra nhng phn t c hiu (enzyme) trong t bo v vai tr xc tc cho qu trnh bin i nng lng cn thit cho hot ng sng ca t bo (Vilan 1903, Vacbua 1908-1913). c bit, sau khi Bensli (1934) dng phng php li tm tch c mt lng ty th thc hnh phn tch ho hc v vt l hc th vai tr ca ty th v enzyme h hp c tr trong ty th mi xc nh c r rng, v c ch qu trnh oxy ho kh trong t bo

mi c khm ph mt cch tng tn. T , cc nh t bo hc ln lt tch c cc cu thnh khc ca t bo nghin cu vai tr ca chng.

Phng php nghin cu nh du ra i cho cc nh t bo hc mt kh nng nghin cu mi: kh nng nghin cu t bo ng ca qu trnh trao i cht trong t bo.

S pht trin ca ho t bo hin nay cho php ta s dng cc phng php phn tch vi ho v siu vi nghin cu cc lng v cng nh ca cc cht, ca tng t bo v c cu thnh ca t bo. Ngy nay, p dng phng php sc k, phng php quang ph, phng php hunh quang hp th tia rnghen cho php ta nghin cu thnh phn ha hc ca mng, cc cht quan trng ca t bo nh phn t acid nucleic, protein... trong tng phn khc nhau ca t bo.

Nhng thnh tu khoa hc ca ngnh di truyn hc t bo: Khong gia th k XIX, tnh cht ph bin ca t bo l phn bo c xem l qu

trnh trung tm v c s cho sinh sn t bo. Nh t bo hc v di truyn hc ni ting Wilson (1925) pht biu: c tnh di truyn chnh l s lin tc di truyn bo m bi s phn chia t bo. Cc nh lut c bn ca di truyn c Enzimedel pht minh t nm 1865. Nhng thi k y, cc thnh tu v hiu bit v t bo cn qu ngho nn cha c s vt cht v l lun gii thch c v v vy cng trnh v i ny b lng qun.

Vo u th k XX, s pht trin ca t bo hc t c mc cao, do , c ch phn ly tnh trng di truyn do Enzimedel tm ra c th hiu v gii thch c. Ngi ta bit rng cc t bo sinh dc nguyn thu (non nguyn bo, tinh nguyn bo) l lng bi khc vi cc t bo sinh dc chn l n bi v chu trnh bin i ca nhim sc th trong phn bo gim nhim lin quan cht ch vi hin tng di truyn. V ch sau khi Morgan v cc cng tc ca ng xc nh c n v di truyn gi l gen v xc nh c cc locus bn trong nhim sc th th cc nghin cu thc nghim, cc nh lut di truyn tin ho mi c c s v mi c th tr thnh mt lnh vc sinh hc gi l di truyn hc. Nhng nm gn y pht trin hng nghin cu mi: di truyn phn t v di truyn sinh ho. Ngi ta i su nghin cu hin tng di truyn khng ch mc t bo m cn mc phn t. Ngi ta xc nh c m di truyn, nghin cu s ng m gen, thay i gen hay ghp gen. c nhiu thnh cng ln trong l lun v thc tin.

Nhng thnh tu khoa hc v cc cu trc siu vi ca t bo v sinh hc phn t: Nh s phi hp cht ch gia t bo hc v cc mn: sinh ho, ha l, ha cao

phn t, ng thi p dng cc phng php nghin cu ha l vo sinh hc m nhng nm gn y xut hin nhng nghin cu mi trong sinh hc nh: hnh thi siu vi v sinh hc phn t.

Nghin cu t chc hay cn gi l siu cu trc ca t bo c ngha quan trng bc nht, bi v tt c cc qu trnh sinh l v sinh ho c trng cho vt cht sng u c th hin trong cu trc phn t ca t bo v mc phn t.

Nhng thnh tu ca sinh hc phn t c nh hng ln n s pht trin ca sinh hc hin i.

S xc lp ln mi tng quan rt cht ch gia trnh t sp xp cc acid amin trong mch polypeptid vi hnh th ca phn t protein v vi cc c tnh sinh hc xc nh ca chng.

Lm sng t c ch hot ng ca cc enzyme khc nhau Sng to ra m hnh phn t ADN v lm sng t vai tr ca chng trong hin

tng di truyn v cui cng hnh thnh quan nim hin i v ho hc lp th v cc i phn t.

Nh vy, thnh tu ca sinh hc phn t cho php ta i su vo bn cht ca s sng. Tt c cc c tnh l ha ca cc phn t tham gia vo hot ng sng, cng nh mi tng quan gia cc phn t u c lin h n t chc t bo. Hay ni cch khc, sinh hc phn t c c s t bo hc ca n. V vy m ngy nay hnh thnh nn chuyn ngnh: sinh hc phn t t bo.

Cn phi ch rng, d cho vai tr ca cc i phn t (acid nucleic, protein...) c quan trng n bao nhiu i na i vi s sng th mc phn t ring r cha th hin c s sng m t chc t bo vn l t chc c s nht, nh nht th hin tnh cht sng ca vt cht sng.

3. Cc phng php nghin cu T bo hc

3.1. Phng php hin vi 3.1.1. Knh hin vi thng (knh hin vi quang hc)

phng i knh hin vi quang hc ph thuc vo h thng ng knh: vt knh v th knh.

Khong cch ca tiu bn c th quan st c i vi knh hin vi thng ph thuc vo bc sng nh sng.

phng i mnh nht ca vt knh hin nay l 120 ln v phng i ti a ca th knh l 30 ln. Nh vy, phng i ti a ca knh hin vi quang hc l 120 x 30 = 3600 ln.

Vt nh bao nhiu th knh hin vi quang hc c th quan st c? Ta bit khong cch (do) cho php ti thiu i vi nh sng thng c biu din

bng cng thc: do = 1/3 ( l di bc sng nh sng) di trung bnh ca bc sng nh sng thng l 0,6 (1 micron: = 0,001

mm). Nh vy, do = 1/3 x 0,6 = 0,2 Ngha l i vi knh hin vi thng ch c th quan st thy nhng chi tit ca tiu

bn c khong cch ln hn 0,2 . Vy, mun tng kh nng phng i ca knh hin vi thng cn s dng cc tia

sng khc c di bc sng ngn hn. 3.1.2. Knh hin vi t ngoi

Knh hin vi t ngoi dng tia t ngoi c di bc sng ngn tng kh nng cho php ca knh hin vi thng.

Ngi ta thng dng cc tia vi di bc sng t 275 - 210 nm (1nm = 0,001m).

Kh nng cho php tt nht c th t ti 0,1. nh sng t ngoi khng nhn thy c bng mt thng nn mun thu nh ngi ta phi mc vo knh mt b phn chp hnh hoc dng mn nh hunh quang nh hin ln mn nh.

Dng knh hin vi t ngoi, ngoi kh nng lm tng phng i cn cho php ta nghin cu thnh phn ho hc ca cc cu trc sinh hc m khng cn thit phi qua qu trnh nh hnh v nhum mu. V vy, dng knh hin vi t ngoi c th nghin cu cc i tng sinh hc trng thi sng.

3.1.3. Knh hin vi hunh quang

Hin tng hunh quang l hin tng pht sng ca cc cht khi b kch thch bi nng lng v hp th nng lng . Ngun nng lng cung cp cho vt c th khc nhau.

Hunh quang quang hc: s pht sng do nh sng thng. Hunh quang Rnghen: s pht sng di tc dng ca tia Rnghen. Hunh quang phng x: do cc cht phng x. Hunh quang sinh vt: quan st thy cc c th sinh vt. Trong k thut t bo v m hc, ngi ta s dng nh sng thng lm pht

quang cc i tng nghin cu, v khi cc cht hp th c tia sng th pht sng. i tng nghin cu di knh hin vi hunh quang thng c hai loi: - Cc i tng t bn thn pht ra hunh quang khng cn nhum mu. Loi ny

gi l hunh quang nguyn sinh. V d: vitamin A, B2... - Hunh quang th sinh: c xut hin khi cc i tng nhum mu bng cc

cht hunh quang c bit. V d: acridin, orange,... Phng php thu hunh quang cho php ta nghin cu cc hot ng sinh vt sng,

quan st s xm nhp v phn tn s phn ca cc cht hunh quang din ra trong c th sng trong qu trnh trao i cht bnh thng v bnh l cng nh cc cht tim vo t bo v m. Dng hunh quang c th nghin cu cu trc v thnh phn ha hc ca cc cht nh ADN, ARN trong t bo.

3.1.4. Knh hin vi i pha

Phng php ny cho php ta thu c cc nh r nt ca cu trc t bo sng m knh hin vi thng khng thy c. Phng php i pha da vo nguyn tc cc cu thnh ring bit cc cu trc ca cc tiu bn trong sut khc vi mi trng xung quanh bi ch s chit quang.

Phng php hin vi i pha cho php khng nhng nghin cu c i tng sng hin vi khng qua tiu bn nhum mu m cn phn bit c cc cu trc trong t bo sng, nghin cu c cc qu trnh sng din ra trong t bo sng nh qu trnh

thc bo, cc thay i ca nhn v t bo cht trong thi k phn chia; s chuyn ng ca ty th.

Ngoi ra, nghin cu t bo sng, ngi ta cn dng hin vi giao thoa, hin vi nn en v k thut hin vi phn cc.

3.1.5. Knh hin vi in t

im khc nhau c bn gia knh hin vi thng v knh hin vi in t l cc tia sng c thay th bng cc chm tia in t c bc sng ngn hn nhiu ln, do tng kh nng phng i ln nhiu ln.

S biu din kch thc ca i tng nghin cu ca cc phng php nghin cu:

1mm

100 10 (t bo ln, hng cu)1 (vi khun)

1000

100

10

Siu vi khun

Phn t protein

Min ca mt thng

Min ca knh hin vi quang hc

Min ca knh hin vi in t

V kh nng l thuyt, khong cch cho php ti thiu ca knh hin vi in t khong 100.000 ln b hn knh hin vi thng. iu cho chng ta kh nng rng ln tng phng i n hng triu ln.

H thng knh hin vi in t, v nguyn tc chung, ging nh h thng knh hin vi thng, ch khc ngun sng ti (chm tia in t) .

K thut hin vi in t m ra chn tri mi trong nghin cu th gii siu vi ca t bo. K thut hin vi in t cho php ta khm ph ra rt nhiu iu mi l trong cu trc siu vi ca t bo. V d: mng li ni bo, th ribo, lizo... pht hin ra cu trc ca mng t bo, mng nhn, cu trc nhn...

3.2. Phng php Rnghen Phng php phn tch cu trc bng tia Rnghen cho php chng ta phn bit

c cc cu trc t 10 tr xung. Phng php ny da trn c s hin tng nhiu x ca tia Rnghen, xut hin khi cc tia phng x Rnghen ng vo nguyn t v phn t to mng khng gian trong vt cht. Khi cc chm song song ca tia Rnghen xuyn

qua i tng nghin cu th nh nhiu x s c ghi ln phim nh t sau i tng nghin cu.

Nh phng php ny ngi ta phn bit c cu trc khng gian phc tp ca hng lot protein v nh n m Watson v Crick xy dng c m hnh cu trc khng gian ca ADN.

y l mt trong nhng phng php hin i tt nht ca cc nh sinh hc phn t, m ra con ng v cng rng ln cho s pht trin ca sinh hc phn t.

3.3. Phng php t bo

Nhim v ca t bo hc khng ch xc nh bng sinh ho ca t bo m ch yu l xc nh cu trc sinh ha phc tp nh khu trong t bo c v s lng cng nh cht lng.

3.3.1. Phng php tch cc cu thnh ca t bo

Ngi ta thng nghin t bo trong mi trng nc, sau li tm tch cc phn khc nhau ca t bo da trn s khc nhau v hng s lng ca cc cu thnh.

Ngy nay, vi cc my li tm siu tc chit phn v li tm siu tc phn tch c tc khong 60.000 - 70.000 vng/pht v dng cc dung mi khc nhau thch hp, ngi ta khng ch phn tch uc cc cu thnh ca t bo nh: nhn, hch nhn, ti th, lp th, nhim sc th.... m cn phn tch c cu thnh i phn t trong t bo v xc nh c trng lng phn t ca chng. V d: cc i phn t protein, acid nucleic hoc virus, tch mch xon ADN...

3.3.2. Phng php nhum mu ha t bo

Ngi ta da vo c tnh cc cu thnh khc nhau trong t bo s b nhum mu khc nhau khi dng nhng cht mu c trng lm xut hin cc cu thnh khc nhau ca t bo ng v tr ca chng. xc nh c cc cht hoc cc nhm cht khc nhau, ngi ta s dng phng php c trng cho tng cht:

- Dng phng php (phn ng) ha hc ging cc phn ng dng trong ha hc phn tch nhng thch hp nghin cu cc m.

- Dng cc phn ng c trng cho mt s cht. - Dng cc phng php l ho. Ngy nay, ngi ta dng cc phng php khc nhau lm xut hin cc

hydratcarbon, cc lipid, cc protide, cc enzyme, acid nucleic trong t bo v cc cu thnh ca t bo ng v tr tht ca chng. Phng php ny ch cho kt qu nh tnh.

3.3.3. Phng php nghin cu t bo sng

C nhiu phng php nghin cu t bo sng nh: - Phng php vi phu thut. - Phng php nui cy t bo - m italic.

V d: ngy nay, nh vo s hon thin ca phng php nui cy m t bo, ngi ta khng nhng nui cy thnh cng cc t bo ring bit m cn c th nui cy ivitro cc bo quan v thm ch c cc phn t sng na. V ng gp ng k trong vic nghin cu tm hiu c ch phn ha t bo, c ch hot ng ca gen...

3.3.4. Phng php quang ph

Ta bit rng cc cu thnh khc nhau trong t bo hp thu chn lc cc tia hng ngoi, cc tia t ngoi v cc tia sng thng. Nh vy, ngi ta c th dng quang ph k o lng s hp th nh sng ca cc cu thnh t bo. Cng hp th nh sng ca cc cht ph thuc vo nng ca cht . Nh vy, ta c th da vo cc dn liu quang hc tnh ton v a ra thnh phn ha hc ca t bo v nh hng cc cht .

Ngy nay, vi phng php ny, ngi ta xc nh c cc cht trong t bo vi lng 10-12 - 10-14 g trong din tch 1 m2. Kt hp vi cc phng php khc nh knh hin vi hunh quang cho php ta nghin cu s phn b trong t bo cc cht protide cc lipid, cc micropolysaccharide cng nh acid nucleic.

3.3.5. Phng php nghin cu t nh du v t chp hnh

Phng php ny da trn nguyn tc s dng cc cht ng v phng x phng ra cc tia , v cc tia ny t nh tng giy nh. Ngi ta a ra cc ng v phng x (C14, P32 v tritium H3...) vo t bo, tiu bn t bo t nh tng giy nh (t chp hnh), sau , em ra nh bng cch thng thng. Da vo nh chp, ngi ta xc nh chnh xc v tr, mt cc phn c cht phng x.

Phng php ny khng nhng cho php chng ta bit c s phn b cc cht trong t bo m cn cho php chng ta theo di c s phn v tnh cht ng hc ca cc cht trong t bo. V d: nh H3 timidin cho php ta theo di c c ch t ti bn ca ADN, nghin cu s tng hp protein trn cc th ribosome.

3.3.6. Cc phng php thng dng trong sinh hc phn t

Phng php tch chit acid nucleic. Phng php phn tch nh tnh v nh lng acid nucleic. Phng php lai phn t. Phng php PCR. Phng php xc nh trnh t acid nucleic. Phng php in di. Phng php sc k.

TI LIU THAM KHO

I. TI LIU TING VIT

1. Nguyn Nh Hin, Trnh Xun Hu (2000), T bo hc, Nxb i hc Quc gia H Ni.

2. Phm Thnh H (2002), Sinh hc i cng - T bo hc, Di truyn hc, Hc thuyt tin ho, Nxb i hc Quc gia Tp. H Ch Minh.

II. TI LIU TING ANH

3. Bruce Alberts, Dennis Bray, Julian Lewis Martin Raff, Keith Roberts, James D.watson (1983), Molecular biology of the cell Garland Publishing, Inc, New York & London. 4. W.D. Phlipps and T. J. Chilton (1991), A - Level Biology, Oxford

mc lc Trang

M U 5 1. i tng v nhim v ca mn T bo hc 5 2. S lc lch s mn T bo hc 7 3. Cc phng php nghin cu T bo hc 10 Ti liu tham kho 16 Phn I: Thnh phn ho hc ca t bo 17 Chng 1 CC LIN KT HO HC

17

1.1. Thnh phn nguyn t ca t bo 17 1.2. Cc lin kt ho hc trong t bo 17 Chng 2 CC CHT V C

20

2.1. Nc trong t bo 20 2.2. Cc cht khong 20 2.3. Cc cht kh 21 Chng 3 CC CHT HU C

22

3.1. Gluxit 22 3.2. Lipid 26 3.3. Protein 28 3.4. Acid nucleic 33 Ti liu tham kho 40 Phn II: Cu to v chc nng ca t bo 41 Chng 4 I CNG V T BO

41

4.1. Hnh thi ca t bo 41 4.2. Cc dng t bo v cu trc i cng 42 Ti liu tham kho 48 Chng 5 MNG SINH CHT (PLASMA MEMBRANE)

49

5.1. Khi nim v h thng mng sinh hc 49 5.2. Cu to mng sinh cht 49 5.3. Chc nng ca mng t bo 60 Ti liu tham kho 61 Chng 6 T BO CHT V MNG LI NI CHT

62

6.1. T bo cht (Cytoplasma) 62

6.2. Mng li ni sinh cht (Endoplasma reticulum) 63 Ti liu tham kho 65 Chng 7 TY TH (MYTOCHONDRIA)

66

7.1. Cu to hnh thi 66 7.2. Thnh phn ho hc 68 7.3. Chc nng 69 7.4. Ngun gc pht sinh 69 Ti liu tham kho 70 Chng 8 LP TH (PLASTIDE)

71

8.1. Bch lc 71 8.2. Sc lc 73 Chng 9 CC BO QUAN KHC

77

9.1. Phc h Golgi (Golgi complex) 77 9.2. Ribosome 79 9.3. Lysosome 81 9.4. Peroxysome 83 9.5. Glyoxysome 84 9.6. Khng bo (vacuole) 84 9.7. Vi ng (microtubule) 85 9.8. T c (miofibrin) 86 9.9. T nng (tonofibrin) 87 9.10. Tin mao (flagella) v tim mao (cillia) 87 9.11. Thnh v v t bo 88 9.12. Trung th (centrosome) 91 Ti liu tham kho 93 Chng 10 NHN T BO (NUCLEUS)

94

10.1. Cu to ca nhn 94 10.2. Thnh phn ho hc ca nhn 96 10.3. Cu trc hin vi v siu hin vi 97 10.4. Chc nng ca nhn 100 Ti liu tham kho 101 Chng 11 DI TRUYN T BO

102

11.1. Nhim sc th 102 11.2. S phn bo 116

Ti liu tham kho 125 Chng 12 C S PHN T CA DI TRUYN

126

12.1. ADN v m di truyn 126 12.2. Qu trnh ti bn ADN 128 12.3. Phin m 131 12.4. Dch m - tng hp protein 136 Ti liu tham kho 144 Chng 13 TRAO I CHT QUA MNG

146

13.1. S vn chuyn th ng 146 13.2. S vn chuyn tch cc (hot ti qua mng) 152 Ti liu tham kho 159 Chng 14 H HP T BO

160

14.1. i cng v h hp t bo 160 14.2. Cc con ng bin i c cht h hp 160 14.3. Trao i nng lng trong h hp 165 Ti liu tham kho 171 Chng 15 QUANG HP

172

15.1. Nhng khi nim chung v quang hp 172 15.2. C ch quang hp 173 Ti liu tham kho 182

Chu trch nhim xut bn: Gim c: NGUYN XUN KHOT Tng bin tp: HONG HU HA

Ngi phn bin:

GS.TS. Nguyn Nh Hin

Bin tp k, m thut: L Ti Thun

Trnh by ba:

Bi Quang Tin

Ch bn vi tnh:

Thi Th Lun - Vn B Th

T BO HC

In 500 bn, kh 16x24 cm, ti Cng ty in Thng k v Sn xut Bao b Hu - 36 Phm Hng Thi - Tp.Hu. S ng k KHXB 78 - 2006/CXB/65 - 01/HH ca Cc xut bn cp ngy 28/02/2006. In xong v np lu chiu thng 9 nm 2006.

Phn I THNH PHN HO HC CA T BO

Chng 1 CC LIN KT HA HC

1.1. Thnh phn nguyn t ca t bo Mi c th sng t n gin n phc tp u c cu to t t bo. T bo c

cu to nn t cc cht ha hc. Thnh phn ho hc trong t bo rt phc tp, a dng. Trong t bo cha nhiu nguyn t khc nhau vi hm lng rt khc nhau. Trong hn 100 nguyn t ha hc c trong t nhin, trong t bo c mt hn 70 nguyn t khc nhau.

Trong cc nguyn t c mt trong t bo, 16 nguyn t (C, H, O, N, S, P, K, Mg, Ca, Fe, Ca, Cl, Na, Mn, Zn, I) l nhng nguyn t c vai tr quan trng trong vic cu to nn cc thnh phn ca t bo, thc hin cc chc nng sng ca t bo.

Su nguyn t C, H, O, N, S, P c gi l cc nguyn t pht sinh sinh vt v vai tr quan trng ca chng. Cc nguyn t ny chim trn 97% khi lng t bo. T 6 nguyn t ny, cu to nn tt c cc hp cht hu c ca t bo nn c vai tr quyt nh s tn ti ca s sng.

Ngoi 16 nguyn t ch yu trn, trong t bo cn c nhiu nguyn t khc vi hm lng v vai tr khc nhau.

Trong t bo ca cc nhm sinh vt khc nhau, hm lng cc nguyn t cng khng ging nhau. Hm lng cc nguyn t trong t bo cn thay i tu thuc iu kin mi trng (thc vt, VSV), ch dinh dng (ng vt).

1.2. Cc lin kt ho hc trong t bo 1.2.1. Lin kt cng ho tr

Lin kt cng ho tr l loi lin kt ph bin v c vai tr quan trng trong cc hp cht ho hc ca c th sng.

Trong lin kt cng ho tr, hai nguyn t cng b ra cc in t dng chung cho c hai nguyn t. Nu mi nguyn t b ra mt in t dng chung s to nn lin kt n (-), nu b ra 2 in t dng chung s to ra lin kt i (=) v nu b ra 3 in t dng chung s to ra lin kt ba ().

Mt nguyn t c th ng thi b ra cc in t dng chung vi mt s nguyn t khc. Nguyn t c th lin kt vi nguyn t khc cng nguyn t hay khc nguyn t.

Lin kt cng ho tr l loi lin kt quan trng, l lin kt cc nguyn t gn li vi nhau to nn hu ht cc loi hp cht trong c th.

1.2.2. Lin kt ion

Lin kt ion hay cn gi lin kt tnh in l lin kt c to ra bi lc ht tnh in gia 2 ion tri du hay gia 2 nguyn t khc nhau ln v m in.

Gia 2 nguyn t khc nhau ln v m in nh Na v Cl th Cl l nguyn t c m in ln nn c kh nng ht hn 1 in t ca Na sang qu o ca n, lm cho nguyn t tha 1 in t v tch in Cl-. Ngc li, Na c m in rt b nn d nhng hn in t cho Cl tr thnh Na+. Hai ion Na+ v Cl- lin kt vi nhau bng lc ht tnh in to ra phn t NaCl:

Na+ + Cl- NaCl

Lin kt ion to nn nhiu hp cht v c nh NaCl, KCl... Lin kt ion cng c mt trong nhiu hp cht hu c nh trong cu trc bc III ca protein.

1.2.3. Lin kt hyro Lin kt hyro c to ra gia cc nhm c H (NH, OH, ..) vi cc nguyn t c

m in ln nh O, N. Do m in ln nn cc nguyn t O, N to lc ht nguyn t H ca cc nhm NH, OH ... dch gn v pha n, lm cho nguyn t H tr thnh cu ni gia 2 nhm v 2 nhm lin kt li vi nhau nh "si dy ni H2".

Cc lin kt H2 c chiu di xc nh v hng xc nh nn to thnh hnh dng n nh ca phn t. Lin kt H2 l lin kt yu d dng b phn hu bi nng lng nh.

Lin kt hyro l loi lin kt rt quan trng trong cc i phn t nh protein, acid nucleic .. Trong protein, lin kt hyro to nn cu trc bc II ca phn t. Trong acid nucleic, cc nucleotide 2 chui ca ADN hay 2 phn khc nhau ca chui ARN lin kt vi nhau bng lin kt hydro theo nguyn l b sung to nn phn t ADN v ARN.

1.2.4. Lin kt k nc

Trong cc phn t phn cc thng cha cc gc mang in tch tri du v c kh nng lin kt vi cc phn t nc, l gc a nc. Tri li, cc phn t khng phn cc, hay cc phn khng phn cc ca 1 phn t do khng tch in nn khng c kh nng lin kt vi cc phn t nc, l gc k nc, nh gc -CH3. Khi cc gc k nc gn nhau, gia chng hnh thnh lc ht, l lc ht k nc to nn lin kt k nc.

Lin kt k nc c mt trong cu trc ca protein, lipid...

1.2.5. Lin kt hp dn Khi 2 phn t gn nhau vi khong cch ngn d < 5Ao th gia chng xut hin

lc ht hp dn (lc van dervan) lm cho chng ht dnh vo nhau. Loi lin kt ny l c s hnh thnh cu trc bc IV t cu trc bc III ca protein.

Chng 3 CC CHT HU C

3.1. Gluxit

3.1.1. Monosaccharide (ng n)

T cc polyalcol c t 3C n 7C b kh hyro s to ra cc phn t ng n tng ng. Tu theo v tr kh H2 s to ra 2 dng ng:

- Nu kh H2 ti C1 s cho ng dng aldose. - Nu kh H2 ti C2 s cho ng dng catose. Trong nguyn t ng n c cha cc nguyn t C bt i nn c cc dng ng

phn lp th. S lng ng phn lp th c tnh bng cng thc A = 2n . Trong : A l s ng phn, n l s lng nguyn t C bt i c trong phn t.

Ngi ta qui nh ly v tr nhm OH ca nguyn t C bt i xa nhm nh chc nht phn thnh 2 nhm ng phn:

- Nu ti C bt i nhm OH quay pha phi th phn t thuc ng phn D. - Nu ti C bt i nhm OH quay pha tri th phn t thuc ng phn L. a s cc phn t ng c 5C tr ln trong dung dch u c cu trc dng

vng. C 2 loi vng: vng 5 cnh v vng 6 cnh. Khi hnh thnh cu trc dng vng lm xut hin thm mt nguyn t C bt i mi s

xut hin dng ng phn mi. Nhm OH to ra ny gi l nhm OH - glucozid. Nu nhm OH - glucozid quay ln trn th c dng ng phn , nu nhm OH - glucozid quay xung di th to ra dng ng phn .

Trong t bo c nhiu loi monosaccharide khc nhau, trong c mt s loi kh ph bin:

- Triose: aldehyl - glyceric, dioxiaceton. - Tetraose: erytrose... - Pentose: ribose, ribulose, xilulose ... - Cetose: cedoheptulose.

3.1.2. Disaccharide

Disaccharide l ng i do 2 n v monosaccharide lin kt vi nhau to thnh. Lin kt gia 2 monosaccharide l lin kt glucozid. C nhiu loi disaccharide tn ti trong t bo. Trong , ph bin nht l maltose, saccharose, lactore.

- Maltose l loi ng i do 2 phn t .D.glucose lin kt vi nhau bng lin kt (1 - 4) glucozid.

Maltose l thnh phn trung gian cu trc nn tinh bt v cng l sn phm phn

hu tinh bt hay glycogen khng hon ton. - Saccharose l loi ng i do phn t .D.glucose ngng t vi phn t

.D.fructose to nn. Hai monosaccharide ny lin kt vi nhau bng lin kt (1 - 2) glucozid to nn:

O O

O O

CH2OH CH2OH

O

O

CH2OH CH2OH

CH2OH Saccharose l ng n ph bin thc vt, c nhiu trong m d tr ca nhiu

nhm cy nh ma, c ci ng. - Lactose l loi ng i do phn t .D.galactose ngng t vi phn t

.D.glucose to nn. Lin kt gia 2 monosaccharide ny l lin kt (1- 4) glucozid: O O O

Lactose c nhiu trong c th ng vt nht l trong sa. O

CH2OH CH2OH

3.1.3. Polysaccaride Polysaccharide l cc gluxit phc vi phn t rt ln gm nhiu n v

monosaccharide lin kt vi nhau to nn. Polysaccharide khng c v ngt nh monosaccharide hay disaccharide, khng tan trong

nc m ch to dung dch keo. y l nhm cht hu c ph bin v c khi lng ln nht trn tri t. Polysaccharid rt a dng v chng loi. Trong c th sinh vt c rt nhiu loi polysaccharide khc nhau, trong ph bin nht l tinh bt, glycogen, cellulose.

3.1.3.1. Tinh bt

Tinh bt l cht d tr rt ph bin thc vt. C nhiu trong cc m d tr nh ht, c. Tinh bt khng phi l n cht m l hn hp cc chui thng cc phn t amylose v chui phn nhnh l amilopectin. T l 2 nhm cht ny trong tinh bt quyt nh cc tnh cht l - ho ca chng, quyt nh cht lng ca chng ( do, n ...)

* Amylose. Amylose l polysaccharide c to nn t cc phn t .D.glucose. Cc .D.glucose lin kt vi nhau bng lin kt (1 - 4) glucozid to nn chui polysaccharide. Mi lin kt glucozit c to ra s loi mt phn t H2O. Do ch c loi lin kt (1 - 4) glucozid cu to nn amylose nn phn t amylose c cu trc mch thng.

Amylose c to ra t 5000 - 1000 phn t .D.glucose (c khi ch khong 250 - 300 phn t). Chui phn t glucose xon li vi nhau theo hnh xon l xo. S hnh thnh dng xon do hnh thnh cc lin kt hyro gia cc glucose to ra. Mi vng xon c 6 n v glucose v c duy tr bi lin kt hyro vi cc vng xon k bn.

Khong khng gian gia cc xon c kch thc ph hp cho mt s phn t khc lin kt vo, v d nh iod. Khi phn t iod lin kt vo vng xon s lm cho cc phn t glucose thay i v tr cht t v to nn phc mu xanh c trng.

Dng xon ca amylose ch to thnh trong dung dch v nhit thng. Khi nhit cao chui xon s b dui thng ra v khng c kh nng lin kt vi cc phn t khc.

O O O O O O O

CH2OH CH2OH CH2OH

1 on amylose * Amylopectin.Amylopectin c cu to phc tp hn. Tham gia cu to amylopectin

c khong 500.000 n 1 triu phn t .D.glucose lin kt vi nhau. Trong amylopectin c 2 loi lin kt:

- Lin kt (1 - 4) glucozid to mch thng. - Lin kt (1 - 6) glucozid to mch nhnh. C khong 24 - 30 n v glucose trn mch s c mt lin kt (1 - 6) glucozid

to mch nhnh. Trn mch nhnh cp 1 li hnh thnh mch nhnh cp 2, c nh vy phn t amylopectin phn nhnh nhiu cp rt phc tp.

Trong tinh bt t l amylopectin chim khong 80%, cn amylose chim 20%. T l ny thay i cc nhm sinh vt khc nhau.

Tinh bt l nguyn liu d tr trong thc vt. y l dng d tr thch hp nht v tinh bt khng c kh nng thm qua mng t bo nn khng th tht thot ra khi t bo.

3.1.3.2. Glycogen

Glycogen l polysaccharide d tr ng vt, l tinh bt ng vt. Cu trc ca glycogen ging tinh bt nhng mc phn nhnh nhiu hn tinh bt, c khong 8 - 12 n v glucose c mt lin kt (1 - 6) glucozid to nhnh mi.

ng vt v ngi, glucogen c d tr ch yu gan. S phn hu v tng hp glycogen c h thng cc hoocmon iu khin mt cch cht ch iu ho s n nh lng glucose trong mu lun l hng s 1%.

3.1.3.3. Cellulose

Trong cc hp cht hu c c trong c th sinh vt th cellulose c t l cao hn c. N l thnh phn chnh ca thnh t bo thc vt.

Cng nh amylose, amylopectin, cellulose l cht trng hp t nhiu n phn. Thnh phn n phn ca cellulose l .D.glucose. Cc phn t .D.glucose lin kt vi nhau bng lin kt (1 - 4) glucozid thay nhau 1 "sp" v 1 "nga". S thay i v thnh phn v cu to ny dn n s khc bit v tnh cht gia cellulose v amylose. Phn t cellulose khng cun xon nh amylose m ch c cu trc dng mch thng. Cu trc ny to iu kin hnh thnh cc lin kt hyro gia cc phn t cellulose nm song song vi nhau, to nn cu trc mng cellulose v vi si (micro fibrin) trong cu trc mng cellulose ca t bo thc vt. Cc si ny khng tan trong nc, rt bn v c hc nn to nn lp mng cellulose bn chc.

O

O O

CH2OH

3.2. Lipid So vi gluxit, lipid l hp cht phc tp hn v c nhiu chc nng trong c th

sng. Mt c trng chung ca nhm cht ny l cha nhiu nhm CH3 nn chng t hay khng ho tan trong nc m ch ho tan tt trong cc dung mi hu c khng phn cc nh etanol, clorofooc, ete ...

Lipid c nhiu loi khc nhau:

O

O

CH2OH

O

O

CH2OH

Lipid

3.2.1. Lipid n gin

Lipid n gin

Triglyceric Sap Steric

Lipid phc tp

Photpholipid Spingo lipid Gluco lipid ...........

Lipid n gin l nhm lipid cha 2 thnh phn l alcol v acid bo. Tu theo thnh phn alcol m to ra 3 loi lipid n gin khc nhau:

3.2.1.1. Triglyceric (cht bo)

Triglyceric (cht bo) c trong thc vt l du, trong ng vt l m. Thnh phn cht bo gm glycerin v acid bo. Cc acid bo lin kt vi glycerin bng lin kt ester. Glycerin c th lin kt vi 1 acid bo to ra monoglyceric, vi 2 acid bo to ra diglyceric v vi 3 acid bo to ra triglyceric. Thnh phn du, m cha c monoglyceric, diglyceric, triglyceric v mt t acid bo t do, glycerin t do.

M ng vt v du thc vt v bn cht ho hc ging nhau, chng ch khc nhau v thnh phn acid bo. ng vt cha acid bo no v c mch C di nn nhit nng chy cao, cn du thc vt cha acid bo khng no v c mch C ngn nn nhit nng chy thp.

O

O

O

Mono - glyceric

CH2 - O - C - R1 CHOH CH2OH

CH2 - O - C - R1 O

CH2 - O - C - R1 O

CH - O - C - R2

2OH

Di - glyceric

CH

CH - O - C - R2

O

2 - O - C - R3

Tri - glyceric

CH

Du v m l nhng cht d tr trong c th thc vt v ng vt. Du v m l nhng cht c nng lng ln nn chng l cht cung cp ngun nng lng ng k cho c th hot ng. Lp m ng vt cn c tc dng chng rt, iu ho nhit . M, du cn l mi trng ho tan cho mt s cht c hot tnh sinh hc cao nh vitamin, hoocmon nn c vai tr rt quan trng trong c th.

3.2.1.2. Sp Thnh phn ca sp gm 1 phn t acid bo no v mt alcol mch thng bc 1 lin

kt vi nhau bng lin kt ester:

R1 - O - C - R2

O

C nhiu loi alcol v nhiu loi acid bo khc nhau to nn nhiu loi sp khc nhau.

Sp thnh thnh chnh ca cht bo v trn b mt l, trn mt ngoi ca mt s cn trng ...

3.2.1.3. Sterit

Sterit c to ra t 1 phn t alcol mch vng bc 1 v mt acid bo. Alcol ca sterit l sterol. Sterol l mt cht rt quan trng trong t bo ng vt v ngi. T sterol hnh thnh nn nhiu hoocmon quan trng ca c th. Ngoi ra cholesterol l mt loi lipid cng vi phospholipid cu to nn mng t bo.

3.2.2. Lipid phc tp

Lipid phc tp l nhm lipid m trong thnh phn ngoi alcol v acid bo cn c cc cht khc. Tu thnh phn nhm cht ny m to ra nhiu nhm lipid phc tp khc nhau trong quan trng nht l nhm phospholipid.

3.2.2.1. Phospholipid

Phospholipid l nhm lipid phc tp m trong thnh phn, ngoi glycerin, acid bo cn c H3PO4 v mt s nhm cht khc. Trong 3 nhm OH ca glycerin, 2 nhm to lin kt ester vi H3PO4 to nn acid phosphatic. Qua H3PO4 ca acid phosphatic lin kt thm vi cc cht khc s to nn cc loi phospholipid khc nhau.

Trong cc loi phospholipid trn th phosphatidyl - colin (leucitin) c vai tr quan trng hn c. N l thnh phn ca mng t bo. Trong cu trc ca leucitin, 2 phn t acid bo hp dn nhau nn chng cng xp trn cng mt hng. u cui ca acid bo cha gc k nc (CH3) nn hnh thnh nn u k nc ca leucitin. Lin kt gia C2 v C3 ca glycerin c th b quay vn i 1 gc 180o lm cho nhm P phn cc nm v chiu ngc li vi 2 chui acid bo v hnh thnh u a nc ca leucitin. Do cu trc c bit m leucitin l mt phn t va k nc va a nc.

Khi phospholipid trn vi nc, chng c th lm thnh lp b mt hay to mixen. Mt dng cu trc quan trng nht l cu trc lp kp phospholipid. Cu trc ny gm 2 lp lipid quay vo nhau, cc u a nc quay ra ngoi to lin kt hydro vi cc phn t nc xung quanh, cn cc u k nc quay vo trong vi nhau. Tng phn t c th chuyn ng t pha ny sang pha kia mt cch tun hon t do bn trong cc lp ca chnh bn thn n ... S phn b theo dng lp lipid kp ny kh bn vng, y l c s cu trc cho tt c mng t bo.

3.2.2.2. Spingolipid

L lipid phc tp. Thnh phn gm spingorin, alcol, acid bo, H3PO4.

3.3. Protein 3.3.1. Acid amin - n v cu trc protein Thnh phn cu to nn protein l cc acid amin. Acid amin l hp cht hu c

cha 2 nhm c bn: amin (NH2) v cacboxyl (COOH) vi cng thc cu to tng qut l:

H2N - CH - COOH

R Cc Aa c phn bit nhau bi gc R. Trong protein c 20 loi acid amin khc

nhau. Do trong phn t Aa c cha nguyn t C bt i nn tn ti 2 dng ng phn

lp th:

H2N - CH - COOH HOOC - CH - NH2 L.acid amin D.acid amin

Trong 2 dng trn ch c dng L.acid amin mi tham gia cu to protein cn dng D.acid amin ch tn ti t do trong t bo.

3.3.2. Cu to protein 3.3.2.1. Cu to protein bc I T cc acid amin, nh lin kt peptid ni chng li vi nhau to nn chui

polypeptid: Chui polypeptid l c s cu trc bc I ca protein. Tuy nhin, khng phi mi chui

polypeptid u l protein bc I. Nhiu chui polypeptid ch tn ti dng t do trong t bo m khng to nn phn t protein. Nhng chui polypeptid c trt t acid amin xc nh th mi hnh thnh phn t protein. Ngi ta xem cu to bc I ca protein l trt t cc acid amin c trong chui polypeptid. Th t cc acid amin trong chui c vai tr quan trng v l c s cho vic hnh thnh cu trc khng gian ca protein v t qui nh c tnh ca protein.

R R

Phn t protein bc I cha c hot tnh sinh hc v cha hnh thnh nn cc trung tm hot ng. Phn t protein cu trc bc I ch mang tnh c th v thnh phn acid amin, trt t cc acid amin trong chui.

Trong t bo protein thng tn ti cc bc cu trc khng gian. Sau khi chui polypeptid - protein bc I c tng hp ti ribosome, n ri khi ribosome v hnh thnh cu trc khng gian (bc II, III, IV) ri mi di chuyn n ni s dng thc hin chc nng ca n.

3.3.2.2. Cu to protein bc II T cu trc mch thng ca protein (cu trc bc I), hnh thnh cc lin kt ni

phn t, l lin kt hyro lm cho chui mch thng cun xon li to nn cu trc bc II ca protein. Cu trc bc II ca protein l kiu cu trc khng gian ba chiu.

S d chui polypeptid c th cun xon li c l do trong cc lin kt trn chui polypeptid th lin kt peptid (C - N) l lin kt bn vng, cn cc lin kt xung quanh n (C - C) (C - N) l lin kt yu c th quay quanh trc ca lin kt peptid:

O O ----- N C C N C C ---- 12 3

H R H R

Lin kt 1: lin kt peptid l lin kt bn vng. Lin kt 2: lin kt C - C l lin kt yu. Lin kt 3: lin kt C - N l lin kt yu. Do cc lin kt (C - C) (C - N) c th quay quanh lin kt peptid (C - N) nn chui

polypeptid c th cun xon li to cu trc bc II ca protein. C nhiu kiu cu trc protein bc II khc nhau, ph bin nht l xon , gp np

, xon colagen. * Xon . Trong kiu xon ny, chui polypeptid xon li theo kiu xon c. Mi

vng xon c 3,6Aa, khong cch gia 2 Aa l 1,5 Ao. Vy chiu di mt vng xon l 5,4 Ao. Cc Aa lin kt vi nhau bng lin kt hyro to s xon.

Cu trc protein bc II dng xon l xo do nhiu lin kt hyro to nn, nhng nng lng ca mi lin kt rt nh nn xon c th c ko di ra hay co ngn li nh 1 chic l xo. Tnh cht ny cho php gii thch kh nng n hi cao ca cc protein hnh si dng l xo.

Cu trc bc II dng xon l c s hnh thnh cu trc protein hnh cu hay hnh si xon.

* Gp np . T 2 n nhiu chui polypeptid c th hnh thnh cu trc bc II theo dng gp np . Trc ht, tng chui t gp np theo dng cu trc ln sng nh s linh ng ca cc lin kt (C - C) v (C - N) trong chui polypeptid. Sau , gia 2

chui gn nhau hnh thnh lin kt hydro: nhm CO ca chui ny lin kt vi nhn NH ca chui kia to nn mt th thng nht.

Cu trc protein theo dng gp np cho php phn t c th gp li bt k v tr no trong chui, nhng nu ko cng ra d dng b t. protein bc II theo dng gp np l c s to nn phn t protein dng si nh fibrion.

* Xon colagen. Cu trc bc II theo dng xon colagen ch c loi protein colagen. y l dng xon c bit. T 3 chui polypeptid dng xon , chng li xon vo vi nhau to nn si siu xon - xon cp 2.

Cu trc bc II ca protein l s chuyn giao gia cu trc mch thng (bc I) sang cu trc khng gian. Protein dng cu trc bc II cha hnh thnh cc tm hot ng nn cha c hot tnh sinh hc. Bi vy, cc protein chc nng (protein enzyme, protein vn chuyn...) khng tn ti dng bc II ny. Ch c mt s protein cu trc mi tn ti cu trc bc II nh protein vt qua mng, protein trong si c ...

3.3.2.3. Cu to protein bc III

T cu trc bc II, nh cc loi lin kt khc nhau nh lin kt disunfit, lin kt ion, lin kt k nc ni cc Aa cc v tr khc nhau li vi nhau lm cho phn t protein cun xon li cht hn, chuyn t cu trc dng si sang cu trc dng khi (cu, bu dc ..).

Cu trc bc III ca protein to ra ph thuc s c mt cc gc R ch khng cn lin quan n lin kt hydro nh trong cu trc bc II.

Mc cun xon, mc cu trc bc III ca phn t protein ph thuc s c mt v v tr ca cc Aa c kh nng to nn cc loi lin kt ion, disunfit, k nc. Bi vy, thnh phn Aa khc nhau s to nn cu trc bc III khng ging nhau.

cu trc bc III, phn t protein hnh thnh cc trung tm hot ng do c iu kin tp hp cc Aa thch hp li gn nhau to tm hot ng. c tm hot ng nn protein bc III c hot tnh sinh hc v tham gia thc hin cc chc nng sinh hc ca chng nh chc nng xc tc (enzyme), chc nng iu tit (nguyn sinh cht), chc nng vn chuyn ...

3.3.2.4. Cu to protein bc IV

mt s phn t protein cn c cu trc phc tp hn. Trong cc phn t ny, c mt s phn t protein bc III c cng chc nng lin kt li vi nhau nh lin kt hp dn to nn phn t protein ln hn, phc tp hn - protein bc IV.

V d phn t hemoglobin (Hb) gm 4 phn t protein bc III kt hp li: 2 tiu th v 2 tiu th . Mi tiu th l mt phn t protein bc III. Hai phn t dng v dng c cu trc khc nhau lm cho chng c th n khp vo nhau nh lc ht tnh in. Gia cc tiu th khng hnh thnh lin kt cng ho tr nn chng d tch ri ra thnh cc protein c lp cu trc bc III.

3.3.3. Tnh cht, vai tr protein

3.3.3.1. Tnh cht protein

* Tnh cht lng tnh. Do thnh phn protein l cc phn t acid amin, m acid amin l cht lng tnh nn protein cng l phn t lng tnh. Ngoi ra, do trong thnh phn Aa ca protein c 2 nhm:

- Cc Aa acid: trong cu to c 2 nhm COOH, trong 1 nhm dng to lin kt peptid cn mt nhm hnh thnh ion COO-.

- Cc Aa kim: trong cu trc c 2 nhm NH2, trong mt nhm to lin kt peptid cn mt nhm hnh thnh NH3+.

Nh vy, phn t protein va c kh nng phn ly nh 1 acid to COO- va c kh nng phn ly nh mt cht kim to NH3+ nn mang tnh lng tnh.

S phn ly ca protein ph thuc pH mi trng. Nu protein tch in th cc phn t nc s lin kt chung quanh phn t, bi lin

kt ion to nn lp mng bao bc bo v cho protein. im ng in, do protein trung ho v in nn khng c mng nc bao bc, cc phn t b kt vn vo nhau gy hin tng kt ta.

* Kt ta v bin tnh. Khi dung dch protein c pH bng im ng in, lp mng nc khng c to thnh s lm cho cc phn t protein khng tch in kt vn li vi nhau. Hoc do mt tc nhn no lm mt mng nc nh nhit cao, acid c.... cc phn t protein khng c bo v bi mng nc cng b kt vn li - chnh l s kt ta ca protein.

C nhiu tc nhn gy nn hin tng kt ta ca phn t protein nh pH, cc mui v c, cc acid hu c, acid v c, nhit ....

S kt ta c th thun nghch, c th khng thun nghch. S kt ta thun nghch l s kt ta m khi khng cn tc nhn gy kt ta na th protein li tr li trng thi ho tan bnh thng. Kt ta khng thun nghch l dng kt ta m khi khng cn tc nhn gy kt ta, phn t protein vn khng ho tan tr li. V d protein kt ta do mui (NH4)2SO4 khi khng cn tc nhn mui th protein tr li trng thi ho tan. Cn khi kt ta bi nhit cao th d c lm ngui dung dch protein tr li, protein cng khng ho tan c.

Khi phn t protein b kt ta, cu trc khng gian ca phn t b thay i do cc lin kt hyro, cc lin kt ion, lin kt k nc b nh hng.

Mch polypeptid b tho g hnh thnh cc vng cun tha ngu nhin. Cu trc khng gian b ph v, tm hot ng b bin dng khng cn hot ng bnh thng hay mt kh nng hot ng .... Kt qu l tnh cht ca protein b bin i - l s bin tnh ca protein.

S bin tnh cng c kh nng thun nghch v bt thun nghch lin quan n s kt ta thun nghch v bt thun nghch. Cc phn t enzyme khi bin tnh khng cn kh nng xc tc. Cc protein chc nng khng cn hot tnh thc hin chc nng.

3.3.3.2. Vai tr protein

Protein l cht hu c c vai tr c bit trong c th sng. Protein gn lin vi s sng, tn ti cng s tn ti ca s sng. C th tm tt cc chc nng ch yu ca protein nh sau:

- Protein l thnh phn ch yu cu to nn t bo, c bit l cu trc nn mng t bo.

- Protein - enzyme l cht xc tc sinh hc, xc tc cc phn ng ho sinh xy ra trong t bo nn c vai tr quyt nh qu trnh trao i cht-nng lng ca c th.

- Protein ca nguyn sinh cht c vai tr iu tit cc hot ng sng xy ra trong c th. N quyt nh cc tnh cht ca nguyn sinh cht.

- Nhiu loi protein c chc nng vn chuyn nh hemoglobin vn chuyn O2 trong mu, cc cht lm nhim v vn chuyn qua mng ....

- Protein trong c c vai tr vn ng. - Nhiu loi protein l cc loi khng th c to ra trong c th khng li

cc khng nguyn gy bnh gip cho c th min dch vi bnh tt. - Mt s protein l hoocmon nh insulin c vai tr quan trng trong iu tit hot

ng sinh l ca c th (nh insulin iu chnh lng glucose trong mu n nh 1%). Ngoi ra, ty c th m protein cn mt s vai tr c trng khc.

3.4. Acid nucleic 3.4.1. Cu to nucleotide 3.4.1.1. Thnh phn nucleotide Nucleotide c 3 nhm thnh phn: - H3PO4. - Baz nit. - ng pentose. C 2 loi nucleotide: ribo nucleotide v dezoxi - ribo nucleotide. Thnh phn

ca 2 loi nucleotide c phn ging nhau v cng c phn khc nhau:

Thnh phn Ribo nucleotide Dezexi - ribo nucleotide H3PO4 H3PO4 H3PO4Pentose Ribose Dezoxi ribose Baz N A, G, C, U A, G, C, T

3.4.1.2. Cu to nucleotide T 3 nhm thnh phn trn lin kt vi nhau to ra nucleotide. T ng pentose lin kt vi baz nit to nn nucleozid - lin kt ni gia C1 ca

pentose vi N3 (nu l baz pirimidin) hay vi N9 (nu l baz nit purin) l lin kt glucozid (N - C) v loi i 1 phn t H2O.

T nucleozide, nhm OH ca C5 ca pentose lin kt ester vi H3PO4 to nn nucleotide. C 2 nhm nucleotide: ribonucleotide v dezoxiribo nucleotide. Mi nhm c 4 loi nucleotide chnh v nhiu nucleotide him (nucleotide chnh bin i thnh)

Baz nit Ribo nucleotide Dezoxiribo nucleotide

A Adenozin.5' - monoP Dezoxi adenozin5' - mono P

G Guanozin 5' - monoP Dezoxi guanozin 5' - mono P

C Cytidin 5' - monoP Dezoxi cytidin 5' - mono P

T Dezoxi timidin 5' - mono P

U Uridin 5' - mono P

T cc nucleotide mono P c th lin kt thm 1 H3PO4 to ra nucleotide - Di P hay lin kt thm vi 2 H3PO4 to nn nucleotide - Tri P. nucleotide - Tri P l nhm nucleotide c vai tr rt quan trng trong c th, c bit l ATP. Trong cu to ca nucleotide - Tri P c 2 lin kt giu nng lng - gi l lin kt cao nng to ra 2 nguyn t P ngoi cng.

Ngoi cc nucleotide thng trn, trong phn t acid nucleic, c bit trong ARN cn c nhiu nucleotide him do cc nucleotide thng bin i bng nhiu cch:

- Bin i baz nit (metyl ho hay tio ho...). - Bin i pentose (metyl ho). - Thay i cu trc baz N. - Thay i kiu cu trc nucleotide.

3.4.2. Cu to acid nucleic

3.4.2.1. Cu to chui poly nucleotide

T cc n phn nucleotide lin kt li bng lin kt photphodiester to nn chui poly nucleotide. Cc ribonucleotide ni vi nhau cho chui polyribonucleotide, cn cc dezoxiribonucleotide ni vi nhau s to nn chui poly dezoxiribonucleotide.

Lin kt ester c to ra t nhm C3'-OH ca nucleotide trc vi nhm OH cn li ca H3PO4 u 5' ca nucleotide sau. Hai nhm OH loi 1 phn t nc v ni li vi nhau bng lin kt ester. Nh vy, phn t H3PO4 to ra 1 lin kt ester trong nucleotide v 1 lin kt ester ni 2 nucleotide li vi nhau, do gi l lin kt photphodiester.

Chui polynucleotide mang tnh phn cc. u tri lun c nhm P l u 5', u phi lun lun c nhm OH t do ti C3 nn gi l u 3'. Chui polynucleotide ch ni di theo chiu 5'-3', tc l nucleotide mi vo lin kt ko di chui ch c ni thm vo u 3'.

T 4 loi nucleotide (trong ADN l dAMP, dGMP, dCMP v dTMP; trong ARN l AMP, GMP, CMP, UMP) s to nn v s cc chui polynucleotide khc nhau. Cc chui polynucleotide c phn bit nhau bi 3 yu t:

- Thnh phn cc nucleotide. - S lng cc nucleotide. - Trt t sp xp cc nucleotide. T polyribonucleotide to ra ARN, cn t polydezoxiribonucleotide s to ra

ADN.

3.4.2.2. Cu to ADN (aciddezoxiribonucleic)

* c im cu to AND. Phn t ADN c to ra t hai chui polynucleotide - hai chui ny xp song song v ngc chiu nhau. S i song ca phn t ADN bo m c s lin kt b sung gia hai chui qua cc baz nit. Baz nit quay vo pha gia hai chui nn hai chui phi ngc chiu nhau.

S i song cng m bo s n nh cho cu trc phn t ADN. c cc lin kt b sung gia hai chui th hai chui phi song song.

Cc baz nit ca hai polynucleotide lin kt vi nhau bng lin kt hydro theo nguyn l b sung: A chui ny lin kt vi T chui kia bng 2 lin kt hydro v ngc li G chui ny lin kt vi C chui kia bng 3 lin kt hydro.

Tnh cht b sung trn bo m cho hai chui lun song song v khong cch gia hai chui khng i do trong cp baz b sung bao gi cng c mt baz purin c kch thc ln i km mt baz pirimidin c kch thc b.

ADN c nhiu kiu cu trc khc nhau. Mi kiu cu trc tn ti trong iu kin ring v chng c th chuyn i ln nhau khi thay i cc iu kin tng ng. Hin nay, ngi ta tm thy trong t bo ADN tn ti dng B, A, C, D, Z, E... trong , dng B ph bin hn v c vai tr trong c ch truyn t thng tin di truyn.

Thnh phn ca ADN cng rt a dng. S a dng ca chui polynucleotide phn tch trn to nn s a dng ca ADN.

Hnh thi ADN trong t bo cng rt a dng. C loi ADN si n thng, si n dng vng, si kp thng, si kp dng vng ...

Kch thc ADN cng rt a dng, t vi trm cp baz n hng triu cp baz.

* Cu trc khng gian ADN dng B (theo Watson - Crick). Kt hp nhiu cng trnh nghin cu v ADN trc , c bit l nghin cu ca Sachgaff cng nhng nghin cu ca mnh, nm 1953, Watson v Crick cng b m hnh cu trc khng gian ca ADN.

Mc d n nay ngi ta pht hin thm nhiu dng cu trc khc ca ADN, cng nh xc nh c cu trc thc ca ADN c khc so vi m hnh l thuyt ca Watson - Crick, nhng s ra i m hnh ca Watson - Crick tr thnh bc ngot trong sinh hc, bo hiu s ra i ca sinh hc phn t.

Cu trc khng gian ca ADN, theo Watson - Crick, c nhng c im c bn sau:

- Hai chui polynucleotide i song, xon theo chiu phi. - Khung dizoxiriboza v H3PO4 nm ngoi b mt phn t. - Cc baz nit hng vo pha trong chui xon. Mt phng cc baz

nit song song vi nhau v thng gc vi trc phn t. Hai baz nit ca hai chui lin kt vi nhau bng lin kt hydro theo nguyn tc b sung (A = T, G C). Hai cp baz nit gn nhau xp lch gc 36oC.

ng knh chui xon 2 nm. Mt phng hai cp baz nit lin nhau cch nhau 0,34 nm. Mi vng xon c 10 cp baz nit vi chiu di 3,4nm. Kch thc trn l theo tnh ton ca Watson - Crick, l kch thc gc. Gn y, qua xc nh bng thc nghim, ngi ta thy ADN dng B (dng ca Watson - Crick) c trung bnh 10,5 cp baz nit trn mt vng xon v chiu di vng xon l 3,6nm (thay v 10 cp v 3,4nm m hnh Watson - Crick).

Cc dng cu trc ca ADN

Dng cu trc c tnh

B A C Z

Chiu xon Phi Phi Phi Tri

S cp N ca 1 vng 10,0 10,9 91/3 12,0

ng knh vng xon 20Ao 23Ao 19Ao 18Ao

Khong cch 2n 3,4Ao 2,9Ao 3,3Ao 3,4Ao

Chiu di vng xon 34Ao 32Ao 31Ao 45Ao

Gc ca baz nit vi trc 90o 20o 18o

Gc gia hai baz 36o 32,7o 38,6o - 30o

3.4.2.3. Cu to ARN ARN l loi acid nucleic c nhng c im v thnh phn, cu to ging ADN

nhng cng c nhng c trng ring. Thnh phn ARN cha riboza thay v dezoxiribo ADN. Baz nit ca ARN,

ngoi nhng thnh phn ging ADN, cn c U c trng ring ca ARN, T cng c trong thnh phn ca ARN.

n phn ca ARN l ribonucleotide. T ribonucleotide lin kt vi nhau to thnh chui polyribonucleotide. ARN cu to t 1 chui polyribonucleotide nhng cng c nhng on to lin kt b sung gia hai phn khc nhau ca chui, trong , A lin kt vi U thay cho T.

C nhiu loi ARN vi cu to v chc nng khc nhau, ARN thng tin (ARNm), ARN vn chuyn (ARNt), ARN ribosome (ARNr), tin ARN (proARN), ARN phn t nh ca nhn (Nh sng ARN), ARN mi (primer ADN)...

* ARNm. ARNm c tng hp trong dch nhn t ADN. ARNm c i sng rt ngn: procariote ARNm ch tn ti trong vi sau pht khi thc hin xong qu trnh dch m, cn eucariote c th ko di t vi pht n vi ngy. ARNm c ti to rt nhanh v n ch tn ti trong thi gian ca mt thng tin. Mt ARNm c th c c nhiu ln nu tin hnh dch m trn polyribosome.

Kch thc ARNm tu thuc kch thc phn t protein do n ph trch tng hp. S lng ARNm cc t bo khc nhau khng ging nhau. t bo ngi c khong 80.000 - 100.000 ARNm khc nhau trong mt t bo.

ARNm c cu to tng qut nh sau:

- procariote:

P - P - p - 5' AUG AUG AUG 3' protein 1 protein 2 protein 3

- uecariote:

5

(4)

(6)(1) (2) (3) (5) Protein

m G.P.P.P AUG AUG PolyA

ARNm eucariote c cc phn: (1) M. (2) Phn khng m ho. (3) M m u. (4) Phn m ho acid amin. (5) M kt thc (mt trong ba m: UAG, UAA, UGA). (6) ui (gm c on polyA - c khong 150 - 200A).

* ARNt. ARNt c tng hp t dch nhn. ARNt l loi c kch thc b ch c khong 75 - 90 nucleotide vi hng s lng l 4,5s (M = 25000 - 30.000). Trong thnh phn ca ARNt c khong 30 loi nucleotide him, chim 10% tng s nucleotide ca phn t.

Nhim v ca ARNt l vn chuyn acid amin t t bo cht n ribosome tng hp protein , cho nn vi mi acid amin phi c t nht mt ARNt tng ng. Nhng trong t bo, do mt Aa c th m ho bi nhiu b ba, cho nn cng s c nhiu ARNt cng vn chuyn mt loi acid amin.

ARNt c cu trc khng gian c trng. Phn t ARNt c cu trc chia nhiu thu nh dng l ch ba, trong , c on dng vng khng c lin kt b sung, c on hnh thnh lin kt b sung. Ngi ta chia ARNt ra lm 5 vng c thnh phn chc nng khc nhau.

* ARNr. ARNr c tng hp trong nhn con v ngay sau lin kt vi protein to nn cc phn t ribonucleoprotein l cc tin ribosome. Qua qu trnh trng thnh, cc ribonucleoprotein ny chuyn t nhn con ra t bo cht v to thnh ribosome .

TI LIU THAM KHO

1. Phm Th Trn Chu, Trn Th ng (1992), Ho Sinh hc, Nxb Gio dc H Ni.

2. Nguyn Nh Hin, Trnh Xun Hu (2000), T bo hc, Nxb i hc Quc gia H Ni.

3. Nguyn B Lc (2000), Ho sinh, Nxb Gio dc H Ni.

Phn II CU TO V CHC NNG CA T BO

Chng 4 I CNG V T BO

4.1. Hnh thi ca t bo 4.1.1. Hnh dng T bo thng c hnh dng tng i c nh v c trng cho mi loi t bo. V

d: tinh trng, t bo trng, t bo thn kinh, t bo hng cu, cc loi t bo biu m... Tuy vy, c mt s t bo lun lun thay i hnh dng nh: amp, bch cu... Trong mi trng lng, t bo c dng hnh cu nh bch cu trong mu. a s t bo ng vt v thc vt c dng hnh khi a gic, c loi phn nhnh (hnh 4.1).

Hnh 4.1. Hnh dng t bo 1. T bo hnh lng tr; 2. T bo hnh khi vung; 3. T bo dt; 4a. Bch cu

nhn hnh c lc; 4b. T bo lim ph; 5. T bo c trn; 6. T bo thn kinh a cc; 7. T bo hnh lng tr tit nhy; 8. T bo mm kha;

9. Tinh trng; 10. Hng cu; 11. T bo a nhn.

4.1.2. Kch thc Kch thc ca t bo rt khc nhau i vi cc loi khc nhau. Ni chung, t bo

c ln trung bnh vo khong 3 - 30m. Nhng c nhng t bo rt ln c th nhn

thy, s m c nh trng g, trng vt... T bo c kch thc ln nht l trng iu, ng knh t ti 17,5cm. Tri li, a s t bo vi khun c kch thc t 1 - 3m.

Ngy nay, ngi ta khm ph ra mt loi t bo c th xem l nh nht, l t bo microplasma laidlawii c ng knh 0,1m, ch ln hn nguyn t hydro 1.000 ln v gn bng kch thc ca siu vi khun. Trong n ch cha khong 1.000 hoc chc nghn cc i phn t sinh hc v tng hp vi chc cc enzyme khc nhau.

Th tch ca t bo cng rt thay i cc dng khc nhau. T bo vi khun c th tch vo khong 2,5m3. i vi cc t bo ca cc m ngi (tr mt s t bo thn kinh) c th tch vo khong t 200 n 15.000m3. Thng th tch ca cc loi t bo l c nh v khng ph thuc vo th tch chung ca c th. V d: t bo thn, gan ca b, nga, chut... u c th tch nh nhau. S sai khc v kch thc ca c quan l do s lng t bo ch khng phi l do kch thc ca t bo.

4.1.3. S lng t bo S lng t bo trong cc c th khc nhau th rt khc nhau. Sinh vt n bo, c

th ch c mt t bo. Cc sinh vt a bo, trong c th c t vi trm t bo (nh nhm trng bnh xe c 400 t bo) n hng t t bo. V d: c th ngi c 6.1014 t bo ch tnh ring hng cu trong mu ngi cng t ti 23 nghn t.

Tuy nhin, c th a bo d c s lng t bo ln n bao nhiu cng c pht trin t 1 t bo khi nguyn: hp t.

4.2. Cc dng t bo v cu trc i cng Trong thc t, khng tn ti mt dng t bo chung nht cho tt c cc c th sinh

vt, m t bo phn ho nhiu dng khc nhau trong qu trnh tin ho ca sinh vt. Ngy nay, nh k thut knh hin vi in t, ngi ta xc lp c hai dng t bo:

- Dng c nhn nguyn thu (procaryota) c t chc cn nguyn thu, cha c mng nhn.

- Dng t bo c nhn chnh thc (eucaryota).

4.2.1. T bo nhn nguyn thu (procaryote)

Thuc loi t bo nhn nguyn thu c vi khun (bacteria) v vi khun lam (cyamobactena). T bo ca chng c kch thc t 0,5 - 3m, thiu mng nhn, thiu cc bo quan chnh thc nh: lc lp, th lyzosom, phc h Golgi... bn ny, thng tin di truyn c tch trong nhim sc th gm mch xon kp ADN dng vng, nhim sc th ny khng cha cc protide kim, thiu b my phn bo v hch nhn.

V d: t bo vi khun escherichia coli (hnh 4.2).

Hnh 4.2. S t bo ca sinh vt c nhn nguyn thu (theo Lodish)

1. Si ADN; 2 Vch t bo; 3. Plasmic; 4. Metosome; 5. Mng sinh cht; 6. Vch t bo; 7. Khong trng mng bao; 8. Mng ngoi.

Vch t bo

1 2

3 4

5

8

6

7

Vch t bo bao pha ngoi mng sinh cht to nn khung cng vng chc cho t bo; c nhim v bo v s tc ng c hc, gi v c nh hnh dng ca t bo, quan trng hn c l chng chu cc tc nhn bt li, nht l p sut thm thu ca mi trng bn ngoi. vng chc ca vch t bo c c l nh cc tnh cht ca peptidoglucan (cn gi l murein) ch c procaryote. Peptidoglucan c cu to t hai loi ng gn vi mt peptid ngn gm hai acid amin, ch c vch t bo vi khun. Cc ng v cc peptid kt ni vi nhau thnh mt i phn t bao bc ton b mng t bo.

Do phn ng nhum mu violet m ngi ta phn bit c hai loi vi khun: Gram dng hp th v gi li mu v Gram m khng nhum mu.

Vch t bo ca cc vi khun Gram dng nh streptococus rt dy, gm peptidoglucan.

Vch ca t bo Gram m nh E.coli gm 3 lp: mng t bo trong cng, peptidoglucan v lp dy ngoi cng gm lipoprotein v liposaccharide to phc hp lipopolysaccharide.

Di vch t bo l mng sinh cht bao bc t bo cht (hnh 4.3).

Hnh 4.3. Vch t bo vi khun (theo Phm Thnh H)

Mesosome l cu trc do mng t bo xp thnh nhiu np nhn, lm su vo khi t bo cht. C th y l ni gn ADN vo mng.

Trong nguyn sinh cht c vng tng t nhn gi l nucleotide. B gen cha mt phn t ADN ln, vng trn, trn (ngha l khng gn thm protein). Si ADN ca t bo procaryota cng mang b gen xp theo ng thng, cc gen ny xc nh cc c tnh di truyn ca t bo v cc hot tnh thng thng nn cng c gi l nhim sc th. Ngoi ra, t bo procaryote cn c th c cc phn t ADN nh c lp gi l plasmid. plasmid thng cng c dng vng trn.

Cc ribosome nm ri rc trong t bo cht, chng s gn ln mARN tng hp protein.

Phn ln vi khun quang hp cha chlorophyll gn vi mng hay cc phin mng (tm).

Mt s vi khun c cc cu trc lng nh gi l tim mao (flagella) dng bi. T bo procaryota phn b khp ni trn qu t. Chng sinh trng rt nhanh, chu

k mt th h ngn, a dng v sinh ho v rt mm do v di truyn.

4.2.2. T bo nhn thc (eucaryota)

T bo ca tt c cc c th cn li nh: to, nm, ng vt n bo, t bo thc vt v ng vt thuc loi t bo c nhn chnh thc. Nhm sinh vt ny nhn c bc trong mng nhn. Trong t bo cht, h thng mng rt pht trin nh: mng li ni sinh cht, phc h Golgi, cng cc bo quan c mng nh ty th, lp th, lyzosom. Nhn cha hch nhn v nhim sc th. Nhim sc th gm ADN v histon. Qu trnh phn bo rt phc tp nn cn c b my phn bo (hnh 4.4).

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Hnh 4.4. S cu to t bo ca sinh vt nhn tht (theo Lodish)

1. Mng nhn; 2.Mng t bo; 3. Th Golgi; 4. Ty th; 5. Peroxisome; 6. Lysosome; 7.Ti tit; 8. Li ni cht ht; 9. Nhn.

4.2.3. T bo thc vt v ng vt

4.2.3.1. T bo thc vt

T bo thc vt c lp v bao ngoi: polysaccharide (cellulose), trong t bo cht c cha cc khng bo. B my phn bo thng thiu trung t. a s t bo thc vt c lc lp l c quan chuyn ho quang nng thnh ho nng. S phn chia t bo cht thc hin nh s pht trin mt vch ngn mi chia t bo thnh hai phn bng nhau (hnh 4.5).

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45

Hnh 4.5. M hnh cu to t bo thc vt (theo Lodish) 1. Ty th; 2. Mng nguyn sinh cht; 3. T ngoi; 4. Peroxixsom; 5. Nhn; 6.

Hch nhn; 7. Li ni cht ht; 8. Li ni cht nhn; 9. Phc h Golgi; 10. Lysosom; 11. Vi si ; 12. L nhn.

4.2.3.2. T bo ng vt

T bo ng vt thng khng c v bao ngoi, khng c lc lp, phn bo bng s hnh thnh eo tht (hnh 4.6).

Trong c th ng vt, cc t bo phn ho khc nhau ph thuc vo chc nng ring ca chng. cc ng vt n bo, c th ch gm mt t bo, nhng c nhiu c quan nh (bo quan m nhn chc nng khc nhau, ging nh ng vt a bo).

Tt c cc dng t bo khc nhau phn nh tnh cht tin ho a dng ca vt cht sng, cho php t bo thch nghi vi nhng chc nng khc nhau, thch nghi vi nhng iu kin sng khc nhau (bng 4.1).

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8

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Hnh 4.6. M hnh cu to t bo ng vt (theo Lodish)

1. Khng bo; 2. Hch nhn; 3. Nhn; 4. Ni cht ht;

5. Peroxisom; 6. Li ni cht nhn; 7. Lc lp; 8. Ty th; 9. Th Golgi; 10. Si lin bo; 11. Mng sinh cht; 12. Vi si t bo; 13. Vch t bo.

Bng 4.1. So snh gia cc t bo procaryote v eucaryota

Nhm sinh vt TT

Cc im so snh

Procaryota (vi khun, vi khun lam)

Eucaryota (nm, thc, ng vt)

1 Kch thc 1 - 10m 10 - 100m 2 Mng nhn Khng C 3 Cc nhim

sc th Mt vng trn, khng c

protein histon Nhiu, thng, c protein

histon 4 B Golgi Khng C 5 Li ni

sinh cht Khng C

6 Lyzosom Khng C 7 Ty th Khng C 8 Chlorophyll Khng c trong lc lp Trong lc lp 9 Ribosome Tng i nh Tng i to

10 Vi ng, vi si Khng C 11 Lng Khng c cu trc 9 + 2 C cu trc 9 + 2

TI LIU THAM KHO

I. TI LIU TING VIT 1. Nguyn Nh Hin, Trnh Xun Hu (2000), T bo hc, Nxb i hc quc gia

H Ni. 2. Phm Thnh H (1995), Sinh hc i cng - T bo hc, Di truyn hc, Hc

thuyt tin ho, T sch i hc tng hp Tp. H Ch Minh.

II. TI LIU TING ANH 3. Bruce Alberts, Dennis Bray, Julian Lewis Martin Raff, Keith Roberts, James D.

watson (1983), Molecular biology of The Cell, Garland Publishing, Inc, New York& London.

4. Lodish, Berk, Zipursky, Matsudaira, Baltimore, Darnell (1999), Molecular Cell Biology, Media Connected, W.H. Freeman and Company.

5. W.D. Phlipps and T. J. Chilton (1991), A - Level Biology, Oxford University Press.

Chng 5 MNG SINH CHT (Plasma membrane)

5.1. Khi nim v h thng mng sinh hc Tt c cc loi t bo, khng c ngoi l, k c nhng t bo c xem l trn khi

xem di knh hin vi thng u c bao bi ci mng gi l mng sinh cht c cu trc hin vi v phn t ging nhau.

Mng sinh cht l mng lipoproteide bao ph khi t bo cht ca t bo. Mng sinh cht cch ly t bo vi mi trng ngoi bo, thc hin s trao i vt cht v thng tin gia t bo v mi trng.

Mng sinh cht tn ti tt c cc dng t bo procaryota cng nh eucaryota. Ngi ta tm thy nhiu loi virus c lp mng lipoproteide bao bc xung quanh li nucleocapside. Togavirus, Rabdovirus v Mixcovirus, lp mng bao gm lp lipid kp lin kt vi glycoproteide pha ngoi. Mng sinh cht cc dng t bo khc nhau c cu to khc nhau v hm lng cc cht v s phn b ca cc phn t trong mng, c th bin i v siu cu trc thc hin cc chc nng ring bit, nhng u c din cu to chung v thnh phn sinh ho in hnh.

5.2. Cu to mng sinh cht 5.2.1. Thnh phn ho hc ca mng 5.2.1.1. Lipid Lipid trong mng ch yu c hai dng: - Dng lipid phn cc (a nc) - Dng lipid trung tnh (k nc) i vi t bo ng vt (hng cu, m...), lipid chim 40 - 50% trng lng kh.

Trong , dng phn cc gm c phospholipid chim 80% tng s lipid, sphingolipid. Trong cc loi lipid trung tnh c cholesterol v acid bo t do l quan trng hn c.

5.2.1.2. Protein

Ngy nay, ngi ta xc nh c hai loi protide c trong cu trc mng, l: - Dng hnh cu hp th trn b mt ranh gii ca hai pha lipid v protein, hot tnh

enzyme ca mng ch yu ph thuc vo protein ny.

- Dng si, chng cng vi phospholipid gi vai tr ch yu cu to nn mng, lm cho n c tnh n hi cao v mm do v mt c hc.

Hm lng protein thay i tu theo tng loi mng, v d mng t bo c c 65%, mng t bo gan c 85%.

5.2.1.3. Gluxit

Cc gluxit thng gp trong mng t bo gm:

- Polysaccharide c mng t bo ng vt. Ngi ta cho rng chng c vai tr quan trng trong vic xc nh tnh khng nguyn ca b mt t bo.

- Olygosaccharide mc trn cc o protein. C gi thit cho rng n c nhim v gi s n nh ca cu trc mng.

Ngoi ra, cc gluxit cn kt hp vi lipid v pritein to nn glycoprotein v glycolipid.

5.2.1.4. Cc cht khc

- Dng cc ion lin kt c nh vi cu trc mng, quan trng nht l Ca++, ngoi ra cn c Mg++, K+, Na+.

- Dng cc ion t do di chuyn qua mng, hoc tham gia vo cc qu trnh trao i cht xy ra trong thnh phn cu trc mng.

- Nc: nc trong t bo tn ti di hai dng t do v lin kt. Nc lin kt quan trng nht l nc lin kt vi lipoprotein. Phn nc ny khng b mt i ngay c khi ta sy kh t bo.

5.2.2. Cu trc phn t ca mng sinh cht

Thnh phn ch yu ca mng sinh cht l lipid v protein, v vy, c th tm hiu c cu trc phn t ca mng sinh cht, trc ht xt mi quan h gia lipid v protein.

Tt c cc thuyt v cu trc mng sinh hc u tp trung vo vic m hnh ho s tng tc v phn b trong khng gian ca lipid v protein.

5.2.2.1. M hnh cu trc mng ca Davson - Danielli

T lu, ngi ta bit rng lipid v nhiu cht ho tan trong lipid di chuyn d dng gia t bo v mi trng xung quanh. T cho rng mng t bo c cha lipid.

Nm 1925, E.Gorter v F.Grendel chit xut lipid t mng hng cu v ho tan chng vo benzen ri nh dung dch ln trn b mt nc cha trong mt ci khay nh. Khi benzen bay hi, trn b mt nc cn li mt lp mng gm cc phn t lipid phn cc. o in tch ca lp mng

n phn t ny, hai ng thy n gp i in tch b mt ca tt c cc t bo hng cu ban u dng chit xut lipid. Trn c s , hai ng kt lun: "Thnh phn cu trc mng bao gm hai lp phn t lipid.

Da vo tnh thm ca mng, cc kt lun ca Gorter v Grendel, ng thi da vo kt qu nghin cu ca mnh nm 1935, J.Danielli trng i hc Princenton v H. Davson trng i hc Lun n xy dng m hnh cu trc mng u tin.

Theo m hnh ca hai ng th c s cu trc ca mng bao gm hai lp phn t phospholipid nm thng gc vi b mt t bo. Cc nhm phn cc (a nc) quay ra ngoi, hng v nc. Cc nhm khng phn cc (k nc) th quay li vi nhau. Pha

ngoi v pha trong lp phospholipid c mt lp phn t protein hnh cu. Trong , cc nhm phn cc ca protein cng hng ra ngoi v cc nhm khng phn cc hng v pha lipid. Cc phn t protein to nn l cc ca mng.

Theo tnh ton ca cc tc gi th chiu dy ca mng khong 80m v lc tc dng gia 2 mng l lc tnh in (hnh 5.1).

Hnh 5.1. M hnh cu trc mng ca Davson - Danielli (theo Robertis)

1. Gc acid sialic; 2. Mch bn ca oligosacharide; 3. Glycoprotein; 4. Protein cu trc.

Ngoi bo

T bo cht

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3

M hnh cu trc mng ca Davson - Danielli gii thch c tnh bn vng, n hi, tnh thm c chn lc ca mng i vi lipid v cc cht ho tan trong lipid, gii thch c mi quan h ca protein vi cc l cc. Hai ng cho rng hai pha ca mng c bao bc bng protein, trong khi cc l mang in tch c bao bc bi protein s cho php cc phn t nh v mt s ion i qua mng.

5.2.2.2. M hnh khm lng ca Singer - Nicolson Nm 1972, S.J. Singer trng i hc tng hp California v G. L. Nicolson

vin Salk a ra m hnh khm lng (fluid mosaic model).

M hnh khm lng chp nhn quan im ca Davson - Danielli v lp kp phospholipid nh hng: ui k nc vo trong v u a nc hng ra mi trng ngoi cha nc. Nhng s sp xp ca protein hon ton khc m hnh ca Davson - Danielli. Thay v bao bc ly pha ngoi mng th hng lot protein c hiu thm nhp su vo trong mng lm cu ni cho hng lot cc chc nng c bn ca mng.

- Cc protein nm mt ngoi (protein ngoi bin) th khc vi protein nm mt trong, mt s mng hon ton khng c protein ngoi bin.

- Cc protein nh v mt phn hoc hon ton nm trong lp kp phospholipid (ni protein), c nhng v tr nh sau:

+ Mt s nm hon ton trong lp kp phospholipid.

+ Mt s khc c mt phn i qua b mt mng.

+ Mt s khc c mt na nm ngoi lp kp phospholipid, na khc nm na trong lp kp phospholipid.

- Cc protein si nm mt phn trong mng hoc xuyn qua mng.

Mt s xuyn qua ton b lp kp phospholipid, ni vi mi trng nc c hai mt.

Lp kp phospholipid to nn phn chnh ca mng. Trong mng nguyn sinh cht cc c th bc cao, ngoi phospholipid, cn c cholesterol.

im c bit ng ch l: cu trc ca mng khng c tnh n nh. Cc phn t lipid c th di chuyn dc theo mng. Tnh linh hot ln nht ca phospholipid l nhng mng c hm lng phospholipid khng no cao v nhng mng khng cha cholesterol. Khi c cholesterol, n s gn vi phospholipid bn cnh v lin kt chng li vi nhau lm gim tnh linh hot ca chng.

Cc protein cng c th chuyn ng, nhng chm hn nhiu so vi phospholipid. C mt s loi protein ca mng b gn cht vo mt ch, do s lm hn ch tnh linh hot ca mng

Trong m hnh khm lng, cc l trn mng c th hin nh cc ng ng xuyn qua mt hoc mt nhm phn t protein. Kh nng ca

cc protein khng b c nh m tri trong lp kp ca phospholipid gii thch tnh linh hot ca nhiu l trn mng. Tnh cht c bit ca mt s nhm R ca acid amin to cho cc l mng c tnh chn lc cao, ngha l khng phi tt c cc ion hoc cc phn t nh u c th d dng i qua, m mt s khc khng qua c (hnh 5.2).

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Hnh 5.2. M hnh khm lng v cu trc mng sinh cht (theo Philips) 1. Protein si; 2. Mt ngoi ca mng; 3. Cc nhm hydrat bm vo protein hnh

cu; 4. Lp kp lipid; 5. Cc protein bm mng; 6. Protein to l; 7. Protein xuyn mng; 8. Cholesterol lm n nh cu trc mng. 9. Bn trong t bo.

5.2.2.3. Quan im hin nay v cu trc mng

Mc d m hnh khm lng ca Singer v Nicolson thuyt phc nhiu ngi, nhng hin nay, nh c phng php nghin cu hin i, cc nh khoa hc lm sng t thm cu trc ca mng. Theo quan im hin i, mng sinh cht cng c cu to bi lp kp lipid v protein, cng c th l si, hnh cu v phn b linh ng cc v tr khc nhau.

- Lp phn t kp lipid: gi l lp phn t kp lipid v lp ny gm hai lp phn t lipid p st nhau, lm nn cu trc c bn hnh v cu bao bc quanh t bo, chnh v vy m lp phn t lipid kp c gi l phn mng c bn ca mng sinh cht.

Mng lipid c thnh phn cu to v c tnh c bn nh sau: v thnh phn ho hc, mng lipid gm c hai loi: phospholipid v cholesterol. Tnh cht chung ca hai loi ny l mi phn t u c mt u a nc v mt u k nc. u a nc quay ra ngoi t bo hoc vo trong t bo cht tip xc vi nc ca mi trng hoc ca t bo cht; u k nc th quay vo gia, ni tip gip ca hai lp lipid. Tnh cht du u k nc ny lm cho mng lun lun c xu hng kt dnh cc phn t lipid vi nhau cho

u k nc khi tip xc vi nc, lp phn t kp lipid cn khp kn li to thnh mt ti kn cho tt c cc u k nc u c du kn, tch khi nc. Nh tnh cht ny m mng lipid c kh nng t khp kn, ti t hp nhanh mi khi b m ra, x ra hoc tip thu mt b phn mng lipid mi vo mng.

Cc phospholipid: cc phospholipid, ni chung, rt t tan trong nc. C rt nhiu loi phospholipid, chng chim khong 55% trong thnh phn lipid ca mng. Bn loi chnh theo th t t nhiu n t l: phosphatidylcholin, sphingomyelin, phosphatidilethanolamin, phosphatidylserin. Ngoi ra cn c phosphatidylinositol vi t l t hn.

Cc loi phn t ny xp xen k vi nhau, tng phn t c th quay xung quanh chnh trc ca mnh v i ch cho cc phn t bn cnh hoc cng mt lp phn t theo chiu ngang. S i ch ny l thng xuyn. Chng cn c th i ch cho nhau ti hai lp phn t i din nhau, nhng trng hp ny rt him xy ra so vi s i ch theo chiu ngang. Khi i ch sang lp mng i din, cc phospholipid phi cho phn u a nc vt qua lp tip gip k nc gia hai l mng, cho nn c s can thip ca mt hoc mt s protein mng (hnh 5.3).

Khuych tn ngang

S xo trn (him gp)

S un cong

S xoay trn

Hnh 5.3. Cc dng chuyn ng ca phn t lipid trong lp Chnh s vn ng i ch ny to nn tnh lng linh ng ca mng t bo. Hai

lp mng thng cha ni dung phospholipid khc nhau. phospholipid kp (theo Bruce Alberts)

Ngoi chc nng l thnh phn chnh to nn lp mng c bn ca t bo v l thnh phn chnh ph trch s vn chuyn th ng vt cht qua mng, cc phospholipid c coi nh l c s dung np cc phn t protein mng, cc nhnh gluxit trn b mt mng, lm cho mng c thm nhiu chc nng c tnh c hiu (hnh 5.4).

Lng Nht

Hnh 5.4. Lin kt i ca chui hydrotcacbon khng bo ho lm tng trng thi lng ca mng kp phosphlipid v lm cn tr s tp hp cc

chui phn t khc (theo Bruce Alberts)

Chui hydratcacbon thng bo ho

Chui hydrotcacbon khng bo ho c lin kt

kp dng cis

Cholesterol: l loi phn t lipid nm xen k cc phospholipid v ri rc trong hai lp mng. Cholesterol chim t 20 - 30% thnh phn lipid ca mng v mng t bo l loi mng sinh cht c t l cholesterol cao nht. T l cholesterol cng cao th mng cng cng v bt tnh lng linh ng. Cholesterol lm cho mng thm vng chc (nhng dng t bo t bin khng c kh nng tng hp cholesterol nn b tan i nhanh do mng lipid khng tn ti c). Thnh phn cn li ca lipid l glycolipid (khong 18%) v acid bo k nc (khong 2%) (hnh 5.5).

- Cc phn t protein mng t bo: mng lipid m nhn phn cu trc c bn, cn cc chc nng c hiu ca mng th phn ln do cc phn t protein m nhim. Cho n nay, ngi ta pht hin trn 50 loi protein mng (cng c trn mt mng duy nht). T l protein trn lipid l xp x 1 mng t bo hng cu.

Cn c vo cch lin kt vi mng lipid, ngi ta chia protein mng ra 2 loi: protein xuyn mng v protein ngoi vi.

u trc phn t

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Hnh 5.5. Cholesterol (theo Bruce Alberts) A. C

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ui

; B. M hnh cu trc; C. M t cng vi 2 phn t phospholipid trong mt lp; 1. Cc vng steroit; 2. u phn cc;

3. hydrocacbon khng phn cc; 4. Nhm pha l u; 5. Vng cholesterol cng; 6.Vng cht lng b sung.

Protein xuyn mng: gi l xuyn mng v phn t protein c mt phn nm xuyn sut mng lipid v 2 phn u ca phn t th th ra hai pha b mt ca mng. Phn xuyn sut ca mng, tc l phn du trong mng lipid l phn k nc, vn l hnh si nhng c th ch xuyn qua mng mt ln, nhng cng c loi ln vo ln ra xuyn qua mng nhiu ln, c khi ti 6, 7 ln. Cc phn th ra hai pha b mt mng u a nc v nhiu loi phn t protein mng u c u th vo pha t bo cht, l nhm cacboxyl (COO-) mang in tch m nn chng y nhau v cng v vy m cc phn t protein xuyn mng, tuy c di ng nhng vn phn b ng u trong ton b mng t bo (tnh cht ny c thay i khi pH thay i). Protein xuyn mng cng c kh nng di ng kiu tnh tin trong mng lipid. Protein xuyn mng chim 70% protein mng t bo.

Protein xuyn mng c cc loi sau:

+ Glycophorin: mt loi protein xuyn mng c phn k nc xuyn mng ngn, chui polypeptid a nc th ra ngoi mng c mang nhng nhnh oligosaccharide v c nhng nhnh polysaccharide giu acid sialic. Glycophorin chim phn ln cc protein xuyn mng v l thnh phn chnh mang cc nhnh olygosaccharide. Cc olygosaccharide ny to thnh phn ln cc cacbonhydrat ca b mt t bo. Cc glycophorin c th mang cc tn khc nhau. Chc nng ca chng cng a dng nh chc nng ca lp o t bo. S xuyn mng ca glycophorin (hnh 5.6).

Hnh 5.6. S phn t glycophorin ca mng t bo hng cu ngi (theo Bruce Alberts)

1. ng trung tnh; 2. Acid sialic; 3. Khong trng ngoi bo; 4. Lp lipid kp; 5. T bo cht.

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5

+ Protein Band3 xuyn mng: loi ny c nghin cu u tin mng hng cu. l 1 phn t protein di, phn k nc xuyn trong mng rt di, ln vo ln ra n 6 ln. Phn th ra trn b mt ngoi mng t bo cng lin kt vi cc olysaccharide. Phn xuyn mng c nhim v vn chuyn mt s anion qua mng. Phn trong t bo cht gm 2 vng: vng gn vi ankyrin, mt trong cc loi protein thnh vin ca h li protein lt trong mng, vng gn vi enzyme phn ly glucose v gn vi hemoglobin. Vai tr vn chuyn anion Band3 c xem nh l mt phn t c lp. Khi gn vi ankyrin ni h li vo mng lipid th Band3 nh l c i (hnh 5.7).

Hnh 5.7. S hai phn t protein xuyn mng Band3 (theo Bruce Alberts) 1. Khong trng ngoi bo; 2. T bo cht; 3. Lp phospholipid kp.

1

2

3

Protein xuyn mng ny cn c thm cc protein enzyme vn ti hay gp. Tn ca chng ph thuc vo vt cht m chng vn chuyn qua mng.

Protein mng ngoi vi: loi ny chim khong 30% thnh phn protein mng, gp mt ngoi hay mt trong mng t bo. Chng lin kt vi u th ra 2 bn mng ca cc protein xuyn mng. Kiu lin kt ny c gi l hp ph, khng phi l lin kt cng ho tr m bng lc ht tnh in hay bng cc lin kt k nc. V d hng cu: fibronectin l protein ngoi vi; pha ngoi mng cn c actin, spectrin, ankyrin; Band4.1 th pha trong mng. Tt c 4 loi protein ngoi vi ny lm thnh mt mng li protein lt bn trong mng hng cu, bo m tnh bn vng v hnh lm hai mt cho mng hng cu. Spectrin l nhng phn t hnh si xon v l phn si ca li. Li gm cc mt li, mi mt li l mt hnh 6 cnh. Cnh l spectrin. nh gc c 21 loi xen k nhau: loi th nht gm actin v Band4.1, loi th hai gm 2 phn t ankyrin. Mi phn t ankyrin lin kt vi vng gn vi ankyrin ca phn t protein xuyn mng band3 (Band3 lin kt trc tip vi ankyrin, ch chim 20% tng s Band3). V nh vy, li protein lm bng pritein ngoi vi v ni vo mng bng protein xuyn mng.

Nhiu protein mng ngoi vi khc cng c pht hin pha ngoi mng, chng tham gia cng cc olygosaccharide c mt trong lp o t bo v thc hin cc chc nng khc.

Fibronectin l mt protein mng ngoi vi bm mt ngoi mng t bo. Protein ny gp hu ht ng vt, t san h n ngi, cc t bo si, t bo c trn, t bo ni m...

T bo ung th c tit ra protein ny nhng khng gi c n trn b mt ca mng t bo. S mt kh nng bm dnh ny to iu kin cho t bo ung th di c.

- Cacbohydrat mng t bo: cacbohydrat c mt mng t bo di dng cc olygosaccharide. Cc olygosaccharide gn vo cc u a nc ca cc protein th ra ngoi mng. u a nc ca khong 1/10 cc phn t lipid mng (lp phn t ngoi) cng lin kt vi cc olygosaccharide. S lin kt vi cc olygosaccharide c gi l s glycocyl ho - bin protein thnh glycoprotein v lipid thnh glycolipid.

Cc chui cacbohydrat thng rt quan trng i vi s gp khc protein to thnh cu trc bc 3 v do , chng lm cho protein c bn v c v tr chnh xc trong t bo. Khi lin kt vi mt ngoi mng t bo ti phn acid sialic ca protein, phn acid ny tch in lm cho b mt glycoprotein ca t bo mang in tch m. Cc phn t glycoprotein u mang in tch m nn y nhau lm cho chng khng b ho tan vi nhau.

Glycolipid cng vy, c phn cacbohydrat quay ra pha ngoi t bo lin kt vi mt acid gi l ganglyoside - cng mang in tch m v cng vi cc glycoprotein lm cho mt ngoi ca hu ht t bo ng vt c in tch m.

- o t bo (cell coat): c ba thnh phn: lipid mng, protein xuyn mng v protein ngoi vi cng vi cacbohydrat glycosyl ho to nn mt lp bao ph t bo gi l o t bo.

Tnh cht chung l nh vy, nhng tng vng, tng im khc nhau th thnh phn v cu trc rt khc nhau to nn cc trung tm, cc khc nhau ph trch cc chc nng khc nhau nh: nhn din, khng, truyn tin, vn ti... iu ng ch l protein t bo cht khng thy c glycosyl ho. vi khun eubacteria hu nh khng c glycosyl ho.

5.3. Chc nng ca mng t bo 5.3.1. Chc nng bo v 5.3.1.1. Bo v c hc Mng t bo ng vai tr l bc tng kin c ngn cch t bo vi mi trng ngoi,

bo v cc vt cht cha trong t bo c n nh, bo v t bo khi nhng tc ng c hc ca mi trng ngoi. Tt nhin, bc tng ny khng c nh, cng rn m rt mm do, linh hot c th thay i hnh dng, c th chuyn ng, c th i mi thnh phn sinh ha ca mnh.

5.3.1.2. Bo v v mt sinh l Mng ng vai tr iu ha dng trao i t ngoi vo v trong ra. Nh m n

ngn cn khng cho cc vt l, cc k th xm nhp vo t bo.

Khi k th xm nhp vo c th, n c nhim v bt gi v o thi chng ra. V d lymphocyte c nhim v tiu dit k th ca c th.

5.3.2. Chc nng thng tin - min dch Theo Minhina (1978) th chnh cc loi ng nh oligosaccharide, ganglyoside c

trong mng c kh nng tip nhn nhng thng tin a dng v phc tp t mi trng ngoi. Cc thng tin m t bo nhn c l cc cht ha hc, hoocmon, virus... v ngay c cc yu t gy bnh cng tng tc vi oligosaccharide. Cng nh cc ng ny m c th nhn bit c nhng t bo ca mnh v phn bit c t bo l. Chnh iu ny gii thch c s khng dung np min dch trong nui cy m.

5.3.3. Chc nng trao i cht Mng t bo l ni thc hin s trao i cht ca t bo. Hot tnh trao i

cht ca mng th hin r nht mng ty th, mng mng li ni sinh cht, mng ca phc h Golgi.

5.3.4. Chc nng vn chuyn cc cht qua mng Chc nng quan trng hng u ca mng t bo l iu ha s qua li ca cc cht

gia bn trong v bn ngoi t bo. Tt c cc cht di chuyn vo hoc ra khi t bo u phi qua vt cn l mng v mng ca mi loi t bo c chc nng chuyn bit cho cht no i qua, vi tc no v theo hng no. T bo thc hin vic vn chuyn cc cht qua mng bng cc qu trnh t nhin nh: khuych tn, thm thu, s vn chuyn tch cc, qu trnh thc bo (phagocytosis) v qu trnh ung bo (pinocytosis).

Ni dung chi tit v chc nng vn chuyn cc cht qua mng s trnh by k phn III (Sinh l t bo).

TI LIU THAM KHO

I. TI LIU TING VIT

1. Nguyn Nh Hin, Trnh Xun Hu (2000), T bo hc, Nxb i hc quc gia H Ni.

2. Phm Thnh H (1999), Di truyn hc, Nxb Gio dc Tp. H Ch Minh. 3. Phm Thnh H (2002), Sinh hc i cng - T bo hc, Di truyn hc, Hc

thuyt tin ho, Nxb i hc quc gia Tp. H Ch Minh.

II. TI LIU TING ANH 4. Bruce Alberts, Dennis Bray, Julian Lewis Martin Raff, Keith Roberts, James D.

Watson (1983), Molecular biology of The Cell, Garland Publishing, Inc, New York& London.

5. Lodish, Berk, Zipursky, Matsudaira, Baltimore, Darnell (1999), Molecular Cell Biology. Media Connected, W.H. Freeman and Company.

6. W.D. Phlipps and T. J. Chilton (1991) A - Level Biology, Oxford University Press.

7. Roberts et all (1975), Cell Biology, Philadelphila - London - Toronto.

Chng 6 T BO CHT V MNG LI NI CHT

6.1. T bo cht (cytoplasma) T bo cht l khi nguyn sinh cht (protoplasma) nm trong mng t bo v

bao quanh ly nhn. T bo cht ca mt s t bo c s phn ha thnh 2 lp:

- Lp ngoi cht (exoplasma) ngoi vi, mng hn v c nht cao hn.

- Lp ni cht (endoplasma) bn trong v bao quanh ly nhn, cha cc bo quan nh: mng li ni sinh cht, phc h Golgi, ribosome, ty th, lp th, th lido...

Nu loi b cc bo quan th cn li khi t bo cht khng c cu trc - gi l cht nn hay th trong sut (cytosol).

Th trong sut chim gn mt na khi lng ca t bo. Th trong sut c nhiu nc, c th n 85%. Sau nc, protein l thnh phn ch yu. Th trong sut cha ng mt s lng protein si xp li thnh b khung ca t bo. Trong th trong sut c hng nghn enzyme v cha y ribosome tng hp protein. Gn mt na enzyme c tng hp nn trn cc ribosome l cc protein ca th trong sut. Do , nn xem th trong sut l mt khi gel c t chc cao hn l mt dung dch cha enzyme.

Ngoi protein ra, trong th trong sut cn c cc loi ARN nh mARN, tARN chim 10% ARN ca t bo. Trong th trong sut cn c cc cht nh: lipid, gluxit, acid amin, nucleoside, nucleotide v cc ion. Thnh thong c cc ht du v ht glycogen vi s lng thay i v c th mang t vng ny qua vng khc ty hot tnh ca t bo.

Th trong sut gi nhiu chc nng quan trng nh: - L ni thc hin cc phn ng trao i cht ca t bo, l ni gp nhau ca chui

phn ng trao i cht. S bin i trng thi vt l ca th trong sut c th nh hng n hot ng ca t bo.

- Ni thc hin mt s qu trnh iu ha hot ng ca cc cht. - Ni cha cc vt liu dng cho cc phn ng tng hp cc i phn t sinh hc

nh cc gluxit, lipid, glycogen. Mi hot ng sng ca t bo u xy ra trong t bo cht v do cc bo quan

ring bit ph trch v c phi hp iu ha mt cch nhp nhng.

6.2. Mng li ni sinh cht (endoplasma reticulum) Mng li ni sinh cht c pht hin bng knh hin vi in t. Mng li ni

sinh cht c mi loi t bo ng vt v thc vt, gn y, ngi ta cho rng nhng cu trc tng t nh mng li ni sinh cht c nhn thy c vi khun.

6.2.1. Cu to hnh thi

Mng li ni sinh cht ch c m t sau khi c knh hin vi in t. N l mt h thng cc ti nh, hoc ti dt song song v ni thng nhau hnh thnh mt mng li 3 chiu. Mi ng hoc ti u c bc bi mt ci mng lipoproteide c dy khong 75 (tng t mng t bo). V pha ngoi mng li ni sinh cht thng vi mi trng ngoi, v v pha trong n thng vi khong quanh nhn. Lng mng li ni sinh cht thng hp c ng knh t 250 - 500.

Mt ngoi c th c ribosome bm vo, hoc c th nhn khng c ribosome bm. V vy, ngi ta phn bit 2 loi: mng li ni sinh cht c ht v mng li ni sinh cht khng ht hay mng li ni sinh cht nhn (hnh 6.1).

1 2

3

Hnh 6.1. Li ni cht ca t bo gan (theo Krstie) 1. Li ni cht nhn; 2.Li ni cht ht; 3. Li ni cht xoang.

Mc pht trin ca mng li ni sinh cht ty thuc vo tng loi t bo v giai

on hot ng ca t bo. t bo c hot ng ch tit mnh th mng li ni sinh cht pht trin.

6.2.2. Thnh phn ha hc

Mng li ni sinh cht cha: - Phospholipid (35% trng lng kh) - Protein (60% trng lng kh). Protein mng li ni sinh cht bao gm c cc

enzyme, v d nh phosphatase.

6.2.3. Chc nng

Mng li ni sinh cht c cc chc nng sau: - Tp trung v c c mt s cht t ngoi t bo vo hay trong t bo. Nhng

protein do ribosome bm ngoi mng tng hp c a vo lng ng. - Tham gia tng hp cc cht: mng li ni sinh cht c ht tng hp protein, cn

gluxit v lipid do mng li ni sinh cht khng ht tng hp.

- Vn chuyn v phn phi cc cht. Nhng git lipid trong lng rut lt vo trong t bo biu m rut (bng c ch m bo) c chuyn qua mng li ni sinh cht a vo khong gian bo.

- Mng ca mng li ni sinh cht cng gp phn quan trng vo s hnh thnh cc mng ca ty th v peroxysome bng cch to ra phn ln cc lipid ca cc bo quan ny.

TI LIU THAM KHO

I. TI LIU TING VIT

1. Phm Phan ch, Nguyn Vn Ngc, Knh (1984), T bo hc, M hc, Phi sinh hc, Nxb Y hc, H Ni.

2. Nguyn Nh Hin, Trnh Xun Hu (2000), T bo hc, Nxb i hc quc gia H Ni.

3. Phm Thnh H (2002), Sinh hc i cng - T bo hc, Di truyn hc, Hc thuyt tin ho, Nxb i hc quc gia Tp. H Ch Minh.

II. TI LIU TING ANH 4. Bruce Alberts, Dennis Bray, Julian Lewis Martin Raff, Keith Roberts, James D.

Watson (1983), Molecular biology of The Cell, Garland Publishing, Inc, New York& London.

5. Lodish, Berk, Zipursky, Matsudaira, Baltimore, Darnell (1999), Molecular Cell Biology, Media Connected, W.H. Freeman and Company.

6. W.D. Phlipps and T. J. Chilton (1991), A - Level Biology, Oxford University Press.

Chng 7 TY TH (Mitochondria)

Ty th c pht hin v m t u tin bi Altman t nm 1894 v n nm 1897

Benda t tn l mitochondria. Cu trc siu hin vi ca ty th c Palad nghin cu bng knh hin vi in t vo nm 1952 v Sjostand vo nm 1953.

7.1. Cu to hnh thi Hnh dng chung ca ty th trong cc loi t bo khc nhau th rt khc nhau v

thng c dng si, ht hoc c si v ht trong mt t bo. V d: trong t bo gan, ty th c th thay i t dng ht sang si v ngc li; cn trong t bo biu b rut, dng si nm phn ngoi, dng ht nm phn trong (hnh 7.1).

Hnh 7.1. Cc dng ty th khc nhau A. Dng ht trong t bo chut; B. Dng si trong t bo thn th;

C - D. Dng si - ht trong t bo gan.

A B C D

Kch thc ca chng cng rt thay i, a s t bo ty th c chiu dy tng i c nh, khong 0,5m, chiu di th thay i v ti a l 7m.

S lng ty th trong cc loi t bo khc nhau th khc nhau v cc trng thi sinh l khc nhau cng khc nhau. V d: trong t bo gan chut c n 2.500, cn trong tinh trng mt s su b ch c 5 - 7 ty th.

Ty th c cu to bi 2 lp mng ging mng t bo.

- Mng ngoi: dy 60, bo m tnh thm ca ty th.

- Mng trong: dy 60. T mng trong hnh thnh nn cc mu li n su vo trong xoang ty th gi l tm hnh rng lc (crista). Mng trong chia xoang ty th thnh 2 xoang.

+ Xoang ngoi nm gia mng trong m mng ngoi rng khong 60 - 80 v thng vi xoang ca cc vch rng lc.

+ Xoang trong c gii hn bi mng trong v cha y cht nn ca ty th gi l matrix.

Cht nn thng l ng nht, nhng i khi quan st thy c cc si mng hoc cc ht nh c mt in t cao, cc ht ny l ni nh cc cation hai ho tr, c bit l Mg+2 v Ca+2.

Cc tm hnh rng lc l nhng vch ngn khng hon ton. S lng cc tm rng lc khng ging nhau nhng t bo khc nhau v cc loi khc nhau.

Mt trong ca mng trong c nhng khi hnh cu ng knh 80 -100 nh vo b mt ca tm hnh rng lc nh mt ci cung di 30 -50 - gi l ht c bn. Trong mt ty th c ti 104 - 105 ht c bn (Vermander - Moran 1963). Ht c bn c 3 chc nng:

- Thc hin phn ng oxy ho kh, gii phng e-

- Vn chuyn e- n tng hp ATP.

- Thc hin phn ng phn gii ATP v cung cp nng lng cho cc hot ng ca t bo (hnh 7.1 v 7.2).

Hnh 7.1. S cu trc chung ca ty th A. Ct b mt phn; B. Ct dc ton b; C. Phng i mt crista; 1. Mng ngoi;

2. Mng trong; 3. Cc vch ngn; 4. Vng ADN; 5. Ribosom ty th; 6. Cht nn; 7. Mng trong; 8. Xoang cha dch; 9. Mng ngoi; 10. Cc ht hnh nm

(ng knh 0,8nm).

C

B

A 12

3

4 5

67

89

10

Hnh 7.2. Ty th ct dc t bo tu di (nh HVDT - theo Fawcett)