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ĐẠI HC THÁI NGUYÊN TRƯỜNG ĐẠI HC NÔNG LÂM Chbiên: TS. TRÂN TTS. TRN T- ThS. CÙ THTHUÝ NGA GIÁO TRÌNH SINH HÓA HC ĐỘNG VT NHÀ XUT BN NÔNG NGHIP HÀ NI - 2008

Idoc.vn Giao Trinh Sinh Hoa Dong Vat

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  • I HC THI NGUYN

    TRNG I HC NNG LM

    Ch bin: TS. TRN T

    TS. TRN T - ThS. C TH THU NGA

    GIO TRNH SINH HA HC NG VT

    NH XUT BN NNG NGHIP

    H NI - 2008

  • LI NI U

    Sinh ho hc ng vt l mt mn hc c s ca nhiu chuyn ngnh trong cc trng i hc nh chuyn ngnh Sinh hc, Chn nui Th y, Nui trng thy sinh Cng ngh sinh hc . . . y l mn hc c tnh cht bc cu gia khoa hc c bn nh sinh hc, ho hc vi khoa hc chuyn ngnh nh dinh dng hc, di truyn hc, cng ngh protein, cng ngh gen, ging vt nui, sinh l hc, bnh l hc... Cho nn, thng qua mn hc ny sinh vin s nm c c s ho sinh v nhu cu dinh dng cng nh ngun gc, nguyn nhn gy bnh ng vt.

    Gio trnh sinh ho hc ng vt do tp th tc gi bin son:

    1. TS. Trn T (Ch bin): Chng 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15

    2. ThS. C Th Thu Nga: Chng 1

    Ni dung ca gio trnh c 15 chng bao gm 2 phn chnh: sinh ho hc tnh v anh ho hc ng . Sinh ho hc tnh s cung cp nhng kin thc c bn v thnh phn v cu to ho hc ca cc cht c trong c th ng vt. Sinh ha hc ng s cung cp nhng kin thc c bn v qu trnh trao i cht, s chuyn hoa ca cc cht v mi lin quan gia cc qu trnh chuyn ha trong c th ng vt.

    Chng ti hy vng rng gio trnh sinh ha hc ng vt ny s l ti liu hc tp b ch sinh vin ngnh Chn nui, Th y ca cc trng i hc Nng nghip, ng thi cng l ti liu tham kho cho cc nh chuyn mn v cc c gi quan tm n lnh vc sinh ha hc.

    Trong qu trnh bin son, chng ti rt c gng tham kho cc ti liu trong v ngoi nc nhm m bo tnh chnh xc, tnh c bn, tnh hin i v tnh thc tin. Tuy nhin, gio trnh s khng trnh khi nhng thiu st. Chng ti xin chn thnh cm n v sn sng tip thu cc hn ng gp t mi tng lp c gi khi tip cn vi gio trnh ny chng ti kp thi b sung, sa cha nhm p ng ngy mt tt hn .

    Tp th tc gi bin son

  • M u

    GII THIU MN SINH HO HC

    1. I TNG V NHIM V NGHIN CU CA MN HC

    Sinh ho hc (Biochemistry) hay cn gi l ho hc sinh vt - l mt mn khoa hc nghin cu hin tng sng, ch yu v mt ho hc. N l mt b phn ca ngnh khoa hc nghin cu v s sng ni chung, tc l ngnh sinh hc.

    S sng bao gm nhiu hin tng rt phc tp c dnh hu n vt l, ho hc, cho: nn hiu c s sng v tin ti iu khin n ta cn phi nm c cc qu trnh c s ca n. Nhim v ny c hai mn sinh l v sinh ho thc hin. Mn sinh l nghin cu cc hin tng l hc ca s sng, cn sinh ho hc nghin cu cc thnh phn v cc biu hin ho hc ca s sng.

    Sinh ho hc c th chia lm 2 phn: sinh ho hc tnh v sinh ho hc ng vi hai nhim v nghin cu khc nhau.

    1.1. Sinh ho hc tnh

    1.1. 1. Nhim v v i tng

    Nhim v ca sinh ho hc tnh l phn tch nghin cu thnh phn cu to ho hc ca tng loi m bo, c quan, ca tng loi sinh dch trong c th. V mt ny, sinh ho hc gn vi ho hu c, nh n m ta c c khi nim c th v cu trc ca c th sinh vt, cng nh v cc cht bin ho trong qu trnh trao i vt cht.

    1. 1. 2. Phng php nghin cu

    Phng php nghin cu ca sinh ho hc tnh phn ln da trn phng php nghin cu ca ho hu c nh: chit xut v phn tch.

    Ngoi ra, ngy nay ngi ta cn ng dng rng ri cc phng php hin i nh phn tch cu trc bng tia Rn - ghen, phng php siu ly tm, phng php in di... trong vi chc nm gn y c nhng pht hin v vng quan trng.

    1.2. Sinh ho hc ng

    1 .2 .1. Nhim v v i tng

    Sinh ho hc ng c nhim v nghin cu cc qu trnh chuyn ho ca vt cht, cc bin i ca tng m bo trong qu trnh trao i vt cht, c th ni y mi l phn ch yu ca mn sinh ho hc.

    Trit hc Mc L-nin khng nh rng sng l mt hnh ..thc vn ng ca vt cht S vn ng th hin qua cc du hiu chung m chng ta gi l "hot ng sng" nh s kch thch, s sinh sn, s sinh trng v s pht dc, tnh di truyn

  • v bin d... Nhng nu i su vo ta thy nn tng ca cc hin tng sng ni trn vn l qu trnh trao i vt cht.

    Nh sinh l hc Nga S-tr-np (1884) ni: "Theo di c ng i ca nhng cht t ngoi a vo c th (di hnh thc thc n, kh th...), cc bc bin chuyn ca chng cc m bo, c quan v cui cng chng c a ra ngoi di dng cc cht thi, l chng ta din t c lch s s sng".

    Nhng qu trnh chuyn ho ca s trao i vt cht c tin hnh trong cc m bo, cc c quan ca c th. ng vt c nhiu c quan li c chuyn mn ho cao thm v chuyn trch v mt hay mt s phn ng chuyn ho, v mt ny sinh ho hc ng cn c gi l sinh ho hc chc nng.

    V d:

    - Gan chuyn trch v tng hp mt s loi protein, mt s vitamin, kh c cht...

    - C c chc nng phn ho glucose ly nng lng co dn.

    - Thn tham gia qu trnh bi tit ur.

    1.2.2. Phng php nghin cu

    nghin cu sinh ho hc ng ngi ta dng nhiu phng php khc nhau, nhng gp rt nhiu kh khn v cc qu trnh ho hc c th din bin vi tc rt ln v h thng phn ng li v cng phc tp. Hn th na, c th li khng phi l ni m chng ta c th p dng nhng thao tc phn tch th bo.

    u th k XIX ngi ta dng cc phng php nh nghin cu ln men ru, chit xut nghin cu cn bng Nit, nghin cu dch tiu ho... Tuy kt qu nghin cu em li nhng pht hin quan trng nhng nhng phn ng su kn nht vn cn l iu b n i vi sinh ho hc.

    Mi cho ti khi phng php nguyn t nh du ra i th hng lot cc phn ng ca qu trnh trao i cht mi c khm ph v trnh by mt cch c h thng.

    Thng qua cc hiu bit v s sng do sinh ho hc cung cp, ta s tr li tc ng ln s sng mt cch c hiu qu hn. V d: trong chn nui th y, nhng kin thc v trao i vt cht gip ta t chc tt hn vic chm sc v nui dng gia sc; cn bit v s bt thng v ri lon ca chuyn ho s gip ta chn on chnh xc v iu tr hiu qu nhiu bnh gia sc. Ngoi ra, sinh ho hc cn gip ta hiu su hn cc vn chuyn mn nh: sinh l hc, bnh l hc, ni khoa, truyn nhim hc...

    2. V TR MN HC

    Sinh ho hc l mn khoa hc c s c tnh cht bc cu gia khoa hc c bn v khoa hc chuyn ngnh. Sinh ho hc, song song vi sinh l hc, s gip ta hiu su hin tng sng ca gia sc.

  • V tr sinh ho hc trong khoa hc chn nui th y:

    * i vi cn b chn nui: sinh ho hc c mt tm quan trng c bit. Nh c kin thc v sinh ho hc ta s hiu c c s ho hc ca s pht trin ca gia sc; hiu c nhu cu ca tng loi gia sc theo tng giai on pht trin v sinh trng ca n. Do trong vic lp ch chm sc, lp khu phn thc n, hoc trong vic chn ging v lai to, chng ta s c c s l lun su sc v ton din hn.

    * i vi cn b th y: Vic nghin cu sinh ho hc li cng cp thit. Mun cha bnh tt phi hiu c cn bnh, m ngun gc ca hu ht cc bnh thng gp u dnh dng n s ri lon h thng trao i cht ca c th. V d nh cc bnh v thiu sinh t, ri lon ni tit t, cc bnh v ng tiu ho . . .

    3. LCH S PHT TRIN CA SINH HA HC

    Sinh ho hc l mn khoa hc c nhp pht trin rt nhanh chng. N c hnh thnh r rt ch mi trn di 100 nm nay, gc r ca n bt ngun t cc mn khoa hc khc nh ho hc, l hc, y hc, sinh hc...

    Nhng mm mng u tin ca sinh ho hc c hnh thnh khi con ngi bit ngh ti vic ch thuc men, nhum vi vc, thuc da th, ru, ct gi thc phm... n th k XVI - XVII nhm y ho hc (tiu biu l Paraxen) ra vic dng cc kin thc ho hc gii thch v can thip vo s sng. H cho rng c th gm ch yu c thu ngn, lu hunh v mui. Nu t l cc cht trong c th thng bng th sc kho tt nu khng s pht sinh bnh tt.

    V d:

    - Lu hunh tng s sinh ra st

    - Lng mui tng s sinh ph thng v tho d

    - Thu ngn tng s sinh bi lit v r.

    Tuy nhin l lun trn n by gi ch cn mang tnh cht lch s, nhng cng lao ca nhm y ho hc ny em li cho thc hnh mt s thuc thu ngn, st, ch... c hiu lc. ng k nht l nhm ny cp n men trao i cht sinh th. Sau do thuyt sinh lc thnh hnh m thuyt ny b hn ch.

    Sang u th k XIX mn ho hc tng hp c hnh thnh. Nhng vic tng hp cc cht c trong c th sinh vt vn cha thc hin c.

    Nm 1828 V-le tng hp c ur t cc cht v c th ranh gii gia th gii v c v th gii hu c mi dn dn c sng t.

    V-le tng hp ur t xyanua mun theo s sau:

  • Sau V-le hng lot cc cht hu c c tng hp. Trong phi k n vic

    tng hp hydrat carbon ca But-le-rp v Fisher, tng hp cht bo ca Bec-t-l.

    Nm 1838 Mun-e bt u c nhng nghin cu t m v ho hc protein.

    Cui th k XIX Fisher v a-nhi-lep-ski ra thuyt mch peptid.

    Th k XIX cng l giai on pht sinh ca cc kin thc v men, vitamin, hormon nh:

    + Kic-gp (1 8 1 4) nghin cu bin i tinh bt thnh ng maltose, tin ra men amylase.

    + Lu-nin (l 854 - 1 937) xc nh vai tr cc vitamin

    + Le-be-ep v Cs-t-trep nghin cu hin tng ln men

    + Tip l cng trnh ca Pap-lp v ho hc chc nng. ng nghin cu thnh phn ho hc ca dch tiu ho v qu trnh tiu ho. ng thi ng cng lm sng t nhiu tnh cht ca cc enzym tiu ho v chng minh vai tr ca h thn kinh trung ng trong qu trnh trao i cht.

    Sang u th k XX nhng .pht hin su sc ca Ba-kh ( 1 857- 1 946) v Paladin (1 859- 1 922) v qu trnh oxy ho hon nguyn sinh hc km theo hin tng gii phng nng lng lm sng t hng lot vn , trong c vn v s h hp m bo.

    Ngy nay, sinh ho hc tr thnh mt h thng s gm nhiu chi nhnh ln, nghin cu nhng chuyn trong nhiu phm vi. V d ta thy c sinh ho hc ng vt, sinh ho hc thc vt, sinh ho hc vi sinh vt, enzym hc, sinh ho hc di truyn...

  • Chng 1

    THNH PHN HA HC CA T BO V DCH TH C TH NG VT

    Thnh phn ho hc ca t bo v dch th c th ng vt rt phc tp. T th k XVII v XVIII nhiu nh khoa hc nghin cu thnh phn ho hc ca t bo ng vt Mc d, vi quan im ho hc hin i th cc nghin cu y cha tht y , nhng chng cng c ngha khoa hc v thc tin nht nh. Nhng nghin cu ny chng minh rng trong thnh phn ca t bo ng vt v thc vt c protein, lipid, v nhng cht khc m c th s dng cho dinh dng v cc nhu cu khc.

    Na cui th k XVIII, Labiaze khi nghin cu thnh phn nguyn t cc cht chit xut t t bo ng vt v thc vt, nhn thy rng chng c cu to t cc nguyn t nh carbon, hydro, oxy v nh.

    V sau, vi cc phng php phn tch ho hc hin i ch ra rng thnh phn nguyn t cc cht ca c th l rt phc tp. Trong thnh phn ca chng cn tm thy nhng nguyn t khc vi s lng rt khc nhau.

    S phc tp v thnh phn ho hc ca cc t.bo c th ng vt c cc nh nghin cu ho hc hu c chng minh. H tan thy trong t bo ng vt s c mt ca cc cht hu c phc tp nh protein, lipid, glucid v s lng ln cc cht c cu to n gin nh acid amin, amid, acid bo, cc dng aldchyd, ru, ke ton, benzol, pyrol... n th k XIX, trong thnh phn t bo c th ng vt ngi ta tm thy enzym, hormon, vitamin v cc cht c hot tnh sinh hc cao ng vai tr quan trng trong trao i cht.

    1.1. THNH PHN CC NGUYN T CA T BO C TH

    Trong thnh phn cc cht ca t bo ng vt tm thy gn 60 nguyn t. Mt phn cc nguyn t ny c tt c cc ng vt, chng cn thit thc hin cc chc nng sng c bn. Nhng nguyn t khc ch c mt s loi ng vt v n quan trng ch i vi cc loi ng vt nht nh, thng chng xut hin t bo ng vt mt cch ngu nhin v sau li o thi khi c th. ~

    i vi nhm th nht bao gm cc nguyn t: oxy, hydro, carbon, Nit, lu hunh, phospho, calci, nam, kim, do, ma gi, st, km, ng, iod, ma ngan, co ban.

    i vi nhm th hai bao gm: lui, nhm, lum, flo, bc, thu ngn, ch, ni ken, ban, molibden, vng, bo, than, crom... Tt c cc nguyn t ny c tm thy trong c th vi s lng rt nh v khng c tt c cc ng vt.

    Hm lng trung bnh ca mt vi nguyn t trong c th ng tt (% so vi khi lng c th)

  • Nguyn t % Nguyn t %

    Oxy........................ 62,43

    Cacbon.................. 21,15

    Hydro................... 9,86

    Nit..................... 3,10

    Canci.................... 1,90

    Phospho............... 0,95

    Kali..................... 0,23

    Lu hunh............0,08

    Clo...................... 0,08

    Nam.................. 0,080

    Ma gi................ 0,027

    Iod.................... 0,014

    Flo................... 0,009

    St.................... 0,005

    Km.................. 0,003

    Brom................. 0,002

    Nhm................ 0,001

    Kremni.............. 0,001

    ng............... 0,00015

    Qua s liu bng trn cho thy: trong t bo c th ng vt hm lng chnh l oxy, carbon, hydro v nh. T cc nguyn t ny cu to nn cc hp cht hu c ch yu ca t bo l protein, lipid v glucid.

    Nhng ng vt khc nhau c kh.nng tch lu loi nguyn t ny hay loi nguyn t khc trong t bo ca chng. V d, mu ca ng vt c v cha st, mu ca chn khp v thn mm cha ng. Cc t bo ca c th ng vt khc nhau cng c nng cc nguyn t khc nhau. V d, iod tp trung ch yu t bo tuyn gip trng, li t bo phi, ng t bo gan, km t bo. sinh dc, thm t bo thn kinh. .. Ngy nay khng nh rng cc nguyn t vi lng trong c th mc du s lng rt nh, nhng tm thy trong enzym v hormon. V d, trong enzym peroxydase c st, enzym oxydase c ng, trong hormon tyrosin c iod...

    Thnh phn cc nguyn t ca t bo ng vt ph thuc vo loi ng vt, la tui, iu kin sng...

    Hm lng cc thuyn t chnh trong c th mt s loi ng tt (%)

    Nguyn t Mo Chut ch

    Cc bon

    Hydro

    Nit

    20,56

    10,52

    3,31

    10,77

    10,15

    3,21

    7,38

    10,28

    2,17

    Trong thnh phn cc cht cn c cc nguyn t phng x nh: kim, rubidi, man,

  • ri. Kali c ngha c bit khi nghin cu cc tia ~ v '. C th ng vt c kh nng gi cc nguyn t phng' x t mi trng mt thi gian vi hm lng nh.

    1.2. CC HP CHT V C V HU C TRONG C TH NG VT

    Cc nguyn t trong c th di dng cc hp cht v c v hu c vi mc phc tp khc nhau.

    Nhm cht th nht: protein, glucid, lipid, lipoid, nc v mui v c lun lun c trong thnh phn t bo ng vt.

    Nhm cht th hai: amoniac, CO2, u r, acid uric, creatin, glycerin v cc cht khc l cc sn phm phn gii ca nhm cht th nht hay sn phm ca qu trnh tng hp.

    Nhm cht th ba l cc cht c hot tnh sinh hc nh enzym, hormon, vitamin...

    Mt trong nhng lin kt ny trong t bo l dng phn t ho tan, dng th hai l dng ton v dng th ba l trng thi keo.

    Kt qu ca s lin kt cc cht vi nhau ca ba nhm cht ny s to thnh v s cc phc cht c thnh phn phc tp.

    T l phn trm cc cht c bn mt s t bo ng vt c th hin bng sau:

    Bng thnh phn ho hc mt s t bo chnh ca c th ng vt c v (%)

    T bo . c Mu Gan No Da xng

    Nc

    Vt cht kh

    Protein

    Lipid v lipoid

    Lucid

    Cht hu c

    Cht v c

    72-78

    22-28

    18-20

    3,0

    0.6

    1,0

    1,0

    79

    21

    9,0

    1,0

    0,1

    0,14

    0,9

    60-80

    20-40

    15

    3-20

    1-15

    Nhiu

    Khng c

    78

    22

    8,0

    12-15

    0,1

    1,0-2,0

    1,0

    66

    34

    23

    7,.0

    C

    C

    0 6

    20-25

    75-80

    26

    Rt t

    C

    Rt t

    45

    1.3. NC TRONG C TH NG VT

    Nc trong c th ng vt nng nghip chim trung bnh khong 2/3 khi lng c th. Hm lng nc gim dn theo la tui. S phn b nc trong t bo cng khc nhau. C loi t bo chim ti 80% hoc ln hn, nhng c loi t bo ch c 1

  • 0% hoc t hn. Mt phn nc trong c th nm trng thi t do, nhng phn ln trng thi lin' kt. Protein v mt s hp cht khc ca c th tn ti trng thi keo. Nc trong cc h thng keo dng hydrat, mu61 hoc lin quan vi lc trng phng. Loi lin kt ny ca nc rt quan trng i vi c tnh ca n trong t bo ng vt.

    S hiu bit v qu trnh lin kt v bi tit nc do cc t bo ca c th c ngha rt ln trong vic nghin cu s trao i nc ng vt.

    Bng T l nc trong t bo ng vt

    T bo T l T bo T l

    Rng

    Xng

    T bo m

    T bo gn

    T bo sn

    Gan

    T bo m lin kt

    tim

    Thn

    Cht xm ca no

    10

    22

    30

    49

    55

    74

    79

    79

    83

    85

    Cht trng ca no

    Tu sng

    Da

    C

    Lch

    Phi

    Mu

    Bch huyt

    Dch d dy

    Nc bt

    70

    69

    72

    76

    76

    78

    79

    95

    97

    99

  • Chng 2

    PROTEIN

    2.1. I CNG V PROTEIN

    2.1.1. Tn gi

    Protein theo ting Hy Lp "Protos" - c ngha l u tin, quan trng nht, iu cho chng ta thy c vai tr quan trng bc nht ca protein i vi cuc sng.

    2.1.2. nh ngha protein

    Ngi ta thng nh ngha protein theo hai quan im:

    2.1.2.1. Theo quan im ho hc

    Cc nh ho hc cn c vo thnh phn v cu to ho hc ca protein nh ngha. H cho rng protein l nhm cht hu c ln vi hai c im ng ch l:

    - Phn t c cha Nit (azt)

    - Trng lng phn t rt cao.

    C th ni rng: Protein l cht trng phn cao phn t ca cc acid amin.

    2.1.2.2. Theo quan dim sinh vt hc

    Cc nh sinh vt hc li da Vo gi tr dinh dng v tm quan trng ca protein i vi s sng nh ngha. Theo quan im sinh vt hc th protein l cht mang s sng. iu ny c ng-ghen pht trin rt rnh mch trong tc phm ni ting "Chng y rinh v "Php bin chng t nhin". n ghen vit:

    "... S sng l phng thc tn ti ca cc th protein, bn cht ca n bao hm trong hin tng lun lun t ti to nhng cu trc ho hc ca nhng th y". ng vit tip: "Bt c ni no c hin tng sng chng ta u thy n i lin vi th protein v bt c ni no c protein khng qu trnh tan r, chng ta bt buc phi gp hin tng sng", "Ngay nhng sinh vt h ng nht m chng ta bit, bn thn cng l mt ht protein".

    Ni dung nh ngha v s sng ca n ghen:

    - S sng l phng thc tn ti ca protein. Protein y l mt c th hon chnh c t chc, ch khng phi l mt loi protein ring bit no .

    - Th protein y cha ng c lp nucleoprotein.

    - Ni dung chnh ca s vn ng sng l s trao i cht, s t thay c i mi cc nguyn t ho hc m hin tng ny khng th c trong mt cht v sinh. Bn biu hin c th ca s sng l:

    + C kh nng vn ng v p nhn kch thch bn ngoi

  • + C kh nng sinh trng, pht trin v sinh sn

    + C kh nng di truyn v bin d

    + C kh nng trao i vt cht vi mi trng bn ngoi

    Trong tt c 4 biu hin trn th biu hin th t ca s sng l quan trng nht. Bi v c trao i vt cht th c th mi c kh nng vn ng v p ng c cc kch thch, mi c kh nng sinh trng, pht trin, sinh sn v mi c kh nng di truyn, bin d c.

    2.1.3. Cc nguyn t ho hc ca protein

    Qua phn tch ho hc ngi ta xc nh c trong protein c cc nguyn t sau y (tnh theo % vt cht kh):

    - Cacbon:........................ 50,6 - 54,5

    - Oxy:.............................21,5 - 23,5

    - Hydro:.......................... 6,5 - 7,3

    - Nit:............................ 15,0 - 17,6 (trung bnh 16%)

    - Lu hunh:..................... 0,3 - 2,5

    - Phospho:....................... 1,0 - 2,0

    Nhn thy rng Nit lun lun c trong protein mt lng t thay i, trn di 1 6% . Trong thc hnh t l ny c dng vo vic nh lng protein (phng php Kjeldahl).

    s lng protein = S lng N x 6,25 g.

    ( y 6,25 g protein tng ng vi lo Nit).

    Cng do no l nguyn t thng trc ca protein nn trong ngn ng thng ngy ngi ta dng ch "M" hiu ngm l protein.

    Ngoi cc nguyn t ho hc k trn, trong thnh phn protein cn c cc nguyn t vi lng v cc nguyn t siu vi lng. Mc du s lng cc nguyn t trong protein rt thp (khong 0,3.10-3%) nhng chng ng vai tr quan trng trong qu trnh hot ng sng ca ng vt, c bit l trong thnh phn ca enzym v hormon.

    V d:

    Iod c trong tuyn gip trng

    Li c m phi

  • ng c tuyn gan

    Km c tuyn sinh dc...

    2.1.4. Vai tr sinh hc ca protein

    protein gi vai tr rt quan trng trong tt c cc qu trnh sinh hc. ngha ng k nht ca chng c th hin qua cc vai tr ch yu sau y:

    Vai tr to hnh

    Ngoi cc protein lm nhim v cu trc nh v vus, mng t bo, ta cn gp nhng protein thng c dng si nh: fibroin ca t tm, nhn; collagen, elastin ca m lin kt, m xng... Cc cht ny c tc dng to hnh m bo bn v tnh mm do ca cc m lin kt.

    Vai tr xc tc

    Hu ht cc phn ng sinh ha hc xy ra trong c th u do cc protein c bit ng vai tr xc tc. Nhng protein ny c gi l enzym. Mc du gn y ngi ta pht hin c mt loi ARN c kh nng xc tc qu trnh chuyn ha tin ARN thng tin (pro-m ARN) thnh ARN thng tin im ARN), ngha l enzym khng nht thit phi l protein. Tuy nhin, hu ht cc phn ng xy ra trong c th sng u c xc tc bi cc enzym c bn cht protein. V vy, ngi ta thng nh ngha enzym l nhng protein c kh nng xc tc c bit cho cc phn ng sinh ha hc.

    Vai tr bo v

    Protein c chc nng chng li bnh tt bo v c th. l cc protein tham gia vo h thng min dch. c bit nhiu loi protein thc hin cc chc nng ring bit to nn hiu qu min dch c hiu v khng c hiu. Cc protein min dch c nhc n nhiu nht l cc khng th, b th v cc cytokine. Ngoi ra, mt s protein cn tham gia vo qu trnh ng mu chng mt mu cho c th. Mt s loi c th sn xut ra nhng c t c bn cht protein nh enzym nc rn, lectin... c kh nng tiu dit k th bo v c th.

    Vai tr vn chuyn

    Trong c th ng vt c nhng protein .lm nhim v vn chuyn nh hemoglobin, mioglobin, hemocyanin vn chuyn O2, CO2 v H+ i khp cc m bo, cc c quan trong c th. Ngoi ra, cn c nhiu protein khc nh lipoprotein vn chuyn lipid, seruloplasmin vn chuyn ng (Cu) trong mu. Mt trong nhng protein lm nhim v vn chuyn c nhc n nhiu nht l hemoglobin.

    Vai tr vn ng

    Nhiu protein lm nhim v vn ng co rt nh miosin v actin ca si c, chuyn dch v tr ca nhim sc th trong qu trnh phn bo...

  • Vai tr d tr v dinh dng

    Cc protein lm nhim v d tr nh casein ca sa, ovalbumin ca trung, feritin ca lch (d tr st). . . Cc protein d tr ny chnh l ngun cung cp dinh dng quan trng cho cc t chc m, phi pht trin.

    Vai tr dn truyn tn hiu thn kinh

    Nhiu loi protein tham gia vo qu trnh dn truyn tn hiu thn linh i vi cc kch thch c hiu sc t th gic rodopsin vng mc mt.

    Vai tr iu ha

    Nhiu protein c kh nng iu ha qu trnh trao i cht thng qua vic tc ng ln b my thng tin di truyn nh cc hormon, cc protein c ch c hiu enzym... V d in hnh l cc protein repressor vi khun c th lm ngng qu trnh sinh tng hp enzym t cc n tng ng.

    Vai tr cung cp nng lng

    Protein l ngun cng cp nng lng cho c th sng. Khi thy phn protein, sn phm to thnh l cc acid amin, t tip tc to thnh hng lot cc sn phm khc trong c cc cetoacid, aldchyd v acid carboxylic. Cc cht ny u b oxy ha dn to thnh CON v H2o, ng thi gii phng ra nng lng.

    2.2. CU TO HA HC CA PROTEIN

    2.2.1. Acid amin - n v c bn cu to nn phn t protein

    Vo u th k XIX (thi k ca nh ho hc H Lan Mulder) ngi ta cha phn bit c protein ca ng vt v thc vt. Ngi ta tng rng protein l ng nht, ch khc nhau v s lng cc sinh vt.

    Mi cho ti nm 1820 ln u tin Bracono dng kim v acid c thu phn protein nhit cao (100 - 1200c) V thu c Cc acid amin u tin, trong c tinh th glycocol.

    Nm 1871 Lubavin cho thy rng protein di tc dng ca cc dch tiu ho phn tch thnh cc acid amin.

    c bit cng trnh ca Fisher (1901 - 1902) c ngha quan trng v vic nghin cu bn cht ho hc ca protein.

    Tt c cc cng trnh nghin cu trn cho chng ta thy rng: thnh phn phn t ca protein l cc acid amin.

    Ngy nay, ngi ta tm thy hn 200 acid amin khc nhau, nhng trong thnh phn ca protein t nhin thng c 20 loi acid amin.

    2.2.1.1. nh ngha acid amin

    Acid qun l mt acid hu c, m trong mt nguyn t hydro ca gc carbon

  • alfa (Ca) c thay th bi nhm quan (NH2)

    Nu trong mt acid amin c hai nhm qun th nhm quan th 2 nm v tr

    carbon cui cng k t nhm carboxyl (COOH).

    V d:

    2.2.1.2. Hot tnh quang hc ca acid amin

    Ch tr glycin trong phn t cht ny khng c nguyn t carbon bt i, cn tt c cc acid amin cn li u c t nht mt nguyn t carbon bt i (tc l bn ha tr ca n c bo ha bi bn nhm nguyn t khc nhau - k hiu C*), do chng u c kh nng lm quay mt phng phn cc ca nh sng, ngha l chng u l nhng cht hot quang.

    Tt c cc acid amin c trong thnh phn protein u c cu hnh L nguyn t carbon a, cc acid amin c cu hnh D rt gp trong thin nhin.

    Ch L cho ta bit cu lluul ca phn t ch khng cho ta bit hng gc quay ca mt phng phn cc .

    - Cc ng phn hu tuyn (lm quay mt phng phn cc sang phi) c k hiu bng du (+)

    - Cc ng phn t tuyn (lm quay mt phng phn cc sang tri) c k hiu bng du (-)

    Ngi ta qui c rng i vi glucid, cht aldehyd D-glyceric c chn lm cht tiu chun so snh, cn i vi acid amin L-serin c chn lm cht tiu chun.

    a s cc acid amin dy D u c v ngt, cn cc acid qun thin nhin thuc

  • dy L - th u c v ng hoc khng v.

    Cc acid amin tng hp u l nhng RAXEMAT khng c tnh hot quang, ngha l mt hn hp cng phn t ca dng D v dng L.

    2.2.1.3. Cc phn ng ho hc c trng ca acid amin * Phn ng vi acid v baz to thnh mui

    ng dng: Do tnh cht lng tnh nn acid qun l nhng cht m tt, n nh

    pa.

    * Phn ng vi acid Nit (hay l phn ng Van-slyke)

    Tr thon v oxyprolin (hai cht ny l iminoacid) cc acid amin u phn ng vi lem no gii phng kh Nit:

    ng dng: Cn c vo lng nh thot ra ngi ta c th tnh c hm lng

    ca cid quan trong dung dch.

    * Phn ng Sorensen (phn ng vi Aldehydformtc -formalin)

    ng dng: Bng cch chun vi dung dch kim tiu chun ngi ta c th xc

    nh c hm lng acid amin c trong dung dch.

    * Phn ng vi kim loi nng

    Acid amin to thnh cc mui phc ni phn t vi cc chun ca kim loi nng, c bit l vi con Cu2+.

  • * Phn ng Sanger

    y l mt phng php ph bin nht dng xc nh acid amin trong mch polvpen~id t u N.

    Khi nghin cu tnh cht ha hc ca acid qun ta thy r nhm a-amin c th trng hp vi dtronuobenzen. Trong mch polypeptid ch c mt nhm a-amin t do. u N, khi trng hp s to thnh dinitrophenyl-polypeptid. Mi lin h ny rt bn vng, do khi dng HCl thy phn protein s gii phng ra tt c cc acid nhn t do cng vi acid amin. nm u N di dng dinitrophenyl-aminoacid (DNP-aminoacid). Sau bng phng php sc k c th d dng nhn bit tn ca acid amin .

    * Phn ng mu vi ninhydrin (trixetohydrinden)

    Khi un nng cc acid D- quan vi ninhydrin, nu mi trng pH < 5 th chng s b oxy ho v phn gii thnh aldchyd tng ng, CO2 v NH3

    Nu pH > 5 th s sinh hp cht mu lc.

    Ngi ta c th tnh c hm lng acid amin tham gia trong phn ng bng cch nh lng kh CO2, NH3 hoc aldehyd va to thnh trong phn ng.

    Phn ng ca acid amin vi ninhydrin c s dng nhiu nh tnh v nh lng acid amin, c bit l phng php sc k trn giy v sc k trn ct nha trao i ln nh my phn tch acid amin t ng do Spackman, Stein v Moose xng. Phn ng ny rt nhy, c th cho php ta xc nh c cc acid amin c nng rt nh (vi microgam).

    2.2.1.4. Phn loi cc acid amin

    C nhiu cch phn loi acid amin. Cc acid amin c th phn loi theo hai quan im: Quan im ho hc v quan im sinh vt hc

    * Quan im ho hc (tc l xt v mt cu to phn t v cc ho tnh), ngi ta thng chia acid amin ra:

  • - Acid amin mch thng: Trong acid amin mch thng ph thuc vo s lng nhm quan (NH2) v nhm carboxyl (COOH) m li chia ra:

    + Acid monoamin- monocarboxylic (cha 1 nhm NH2 v 1 nhm COOH)

    + Acid monoamin- dicarboxylic (cha 1 nhm NH2 v 2 nhm COOH)

    + Acid diamin- monocarboxylic (cha 2 nhm NH2 v 1 nhm COOH)

    - Acid amin mch vng: gm loi vng ng nht v loi d vng.

    * Quan im sinh vt hc (tc l xt tm quan trng i vi s dinh dng ca ng vt). Theo quan im ny, acid amin gm hai loi:

    - Loi khng thay thm c (indispensable amino acid) hay cn gi l acid amin thit yu (essential amino acid - EAA): y l loi acid amin rt cn thit cho c th ng vt cho qu trnh sinh trng v pht trin. C th ng vt khng th t tng hp c tho mn nhu cu ca bn thn m phi thng xuyn a t bn ngoi vo vi thc n

    i vi ng vt ni chung c 9 acid amin khng thay th c: Vang, leucin, isoleucin, treo nin, methionin, phenylalanin, tryptophan, ly sin, histidin.

    Loi thay th c (dispensable amino acid) hay cn gi l acid amin khng thit yu (nonessential amino acid - NEAA): tc l loi acid amin m c th ng vt c th t tng hp c t cc nguyn liu sn c (cc acid bo, amiac, amid...). Nhm ny gm cc acid amin cn li.

    Cn phi ch thm rng khng phi mi acid amin u c tc dng v~ nh hng nh nhau i vi cc loi ng vt m mi gia sc, gia cm c nhng nhu cu c trng ca mnh i vi tng loi acid amin. C loi ng vt cn ti 10 acid amin khng thay th (v d nh i vi g con th arginin l acid tin khng thay th), nhng c loi ng vt li ch cn 8 acid amin khng thay th (v d nh ngi th histidin c xp vo nhm acid amin thay th).

    Mt s acid amin khng c xp vo nhm khng th thay th hay nhm thay th m chng c xp vo nhm bn thay th (sm- dispensable) hay cn gi l bn thit yu (semi-essential). Thuc nhm ny c arginin, cystein, tyrosin. Arginin c coi l bn thay th i vi ln v arginin c th c tng hp t glutamin. Tuy vy, s tng hp ny khng p ng nhu cu dinh dng trong giai on u ca qu trnh pht trin c th. Do khu phn cho ln sinh trng phi cha mt lng arginin nht nh. Nhiu nghin cu cho thy giai on sau khi thnh thc v tnh v giai on mang thai ln c th ng hp arginin vi s lng p ng nhu cu ca chng, nhng khng p ng nhu cu tit sa ca ln ni. Cystein c th c tng hp t methionin. Tuy vy, cystein v dng oxy ho ca n l cystin c th p ng khong 50% nhu cu ca tng lng acid amin cha lu hunh (methionin, cystein). Tyrosin c tng hp t phenylalanin v c th p ng ti thiu 50% tng

  • nhu cu ca tyrosin v phenylalanin, nhng n khng th l ngun duy nht v khng th thay th cho phenylalanin v n khng th chuyn c thnh phenylalanin.

    2.2.1.5. Cc loi acid amin

    C 20 loi acid amin tham gia vo cu trc ca m bo cn c vo nhm quan v nhm carboxyl trong phn t m acid amin chia ra:

    Cc acid amin mch thng:

  • 2.2.2. Kt cu ca cc acid amin trong phn t protein

    (Cc kiu trn kt ca acid amin trong phn t protein)

    Dng phng php thy phn ngi ta tm ra c n v cu to ca protein l acid amin. Trong phn t protein s lng acid amin thng rt ln, cho nn ta cn nghin cu xem chng lin kt vi nhau nh th no.

    2.2.2.1. Cu trc bc mt ca protein - lin kt peptid (-CO - NH-)

  • Cui th k XIX nh sinh ho hc Nga a-nhi-lep-ski ra gi thuyt rng cc acid amin lin kt vi nhau nh bn kt gia nhm carboxyl v nhm quan (- Co - NH -) gi l mch peptid. ng ra thuyt ny khi nghin cu phn ng Biur cc dng protein.

    Gi thuyt ca anhilepski ngay sau c nh sinh ho hc ngi c l

    Fisher xc minh bng thc nghim. Fisher tch ring v nghin cu t m 19 acid amin v th tng hp cc peptid theo kiu phn ng sau y:

    Dng dn xut cloranhydric ca mt acid bo no cho tc dng vi acid qun ta s c mt hp cht trung gian. em n cho tc dng vi amiac ta s thu c mt dipeptid :

    Dng phn ng ny nhn di chui peptid

    Ngi ta thy tnh cht ca cc peptid tng hp c ging tnh cht ca sn phm thu phn protein cha trit . Trong thc hnh ngi ta gi peptid thu phn c l pepton hoc albumose.

    Do ta c th ni: C s cu trc bc mt ca protein l mch peptid (- Co - NH -), mch c hnh thnh gia nhm carboxyl ca acid amin th nht vi nhm quan ca aci quan tip theo sau khi loi khu i mt phn t nc. y l lin kt ng ho tr nn n rt bn vng.

  • Nh phng php nghin cu tinh th bng quang tuyn Rn-ghen ngi ta thy

    nhng mch peptid cu trc bc mt c hnh th v kch thc theo s sau:

    Tu thuc vo s lng acid qun ta c dipeptid, tripeptid, tetrapeptid... v

    polypeptid. Tn gi nhng peptid n gin da theo tn ca acid amin hp thnh, nhng cht c - Co - u bin ui -in thnh -yl cht sau cng c - COOH th gi nguyn tn. V d: glycyl- alanin.

    Tnh c trng ca protein khng nhng ph thuc vo s lng m cn ph thuc vo th t sp xp ca cc acid amin trong chui peptid. Mi protein c s lng v th t sp xp cc acid amin ring v nh vy n c chc nng ring.

    Nu c 3 acid amin A, B v C ta c th sp xp thnh 6 peptid khc nhau ABC, ACB, BC, BCA, CAB, CBA, c ngha l 1. 2. 3 = 6

    Qui tc chung l pH : 1. 2. 3...... n = n !

    Nu c 20 acid qun ta c con s peptid gm 19 ch s sau:

    2.432.902.008.176.640.000

    Cu trc bc mt ca protein l yu t di truyn ht sc n nh. Mi t hp c th t sp xp acid amin khc nhau, ch cn mt acid amin no trong t hp khc i th tnh cht vt l, ho hc v sinh hc ca protein khc i rt xa.

    Ta ly mt vi th d v cu trc bc mt ca protein

    * Hng cu ca ngi c 600 - 640 acid amin. Khi th t ca vlin v acid glutamic v tr th 6 v 7 i ch cho nhau lm cho hng cu t hnh trn bin thnh hnh li lim (m hng cu hnh li lim l mt bnh di truyn v l nguyn

  • nhn gy ra thoi ho ging).

    * Phn t insulin l mt polypetid bao gm 5 1 acid amin chui A c 2 1 gc acd quan v chui B c 30 gc acid amin. Hai chui ni vi nhau bi 2 cu dsulfit: cu th nht gia gc cystein v tr 20 ca chui A v v tr 19 ca chui B; cu th hai gia gc cystein vi t th 7 ca c 2 chui.

    cc ng vt khc nhau, chng ch khc nhau acid amin th 8, 9, 10.

    8 9 10

    B Alanin Serin Valin

    Ln Treonin Serin Isoleucin

    Cu Alanin Glycin Valin

    * Ocytocin v vasopressin l hai loi hormon ca thu sau tuyn yn, chng u c 9 acid amin, nhng sp xp ch khc nhau v tr s 3 v s 8.

    Ocytocin c tc dng lm tng co bp c trn t cung, cn vasopressin lm tng

    huyt p ng mch, chng li tiu.

    Vic pht hin ra cu trc bc mt ca cc protein l mt thnh tu rt ln trong ho hc protein. N l cu trc quan trng nht, quyt nh hnh dng v hot tnh sinh hc ca cc protein khc nhau. Tnh mun hnh mun v ca protein trc ht l c tnh sinh hc ph thuc vo cu trc bc mt. Hin tng c trng sinh hc chnh l s khc nhau v cu trc v chc nng ca protein v l nguyn do ca tnh c trng, c th ca sinh vt, tc l khc nhau v loi, ging, tng c th v cc b phn trong tng c th

    Qu trnh di truyn sinh vt chnh l hin tng truyn t li cho i sau cu trc bc mt ca protein c th ca loi ging.

    Cu trc ca proten c m ho qua thit k m di truyn acid nucleic.

    2.2.2.2. Cu trc bc hai ca protem - lin kt hydrogen

    Lin kt hydrogen c pht hin nh phng php quang ph (phn hng ngoi b mch ny hp ph).

    Lin kt hydrogen thng xut hin trong nhng hp cht c hin tng phn cc r rt trong phn t.

    V d nc, do s phn cc m nguyn t oxy c in tch m d v hydro c in tch dng d. Khi hai phn t nc nm gn nhau n mt mc nht nh, gia cc in tch d i du ca chng s xy ra lin kt ph, gi l lin kt

  • hydrogen. c tnh ca lin kt ny l khng c nh m c tnh linh ng, lc lin kt ca n yu gp 10 - 12 ln so vi lin kt ng ho tr.

    Trn mt phng c th biu din lin kt hydrogen do cc nhm - Co - NH - ca

    hai chui petid nh sau:

    Da vo s liu v kch thc phn t v gc to nn bi cc gc acid amin,

    ngi ta cho rng chui peptid trong protein t nhin thng cun theo hnh xon c. C nhiu kiu xon c nh , , ... Nhng loi xon c kiu (alfa) c nhiu ngi cho l gn chn l nht. c im ca loi ny l mch hydrogen gia cc lin kt peptid chim s ng, to cho xon c th n nh nht v nhng nguyn t sinh lin kt peptid - CO - NH - u nm trong mt mt phng.

    - Nhiu protein ca c, mu, cc m mm cha cc on xon chui peptid cun li theo hnh l xo, to thnh nhng bc xon. Bc xon cha 3,7 gc acid amin.

    - Dng gp np l cu trc bc hai c trng cho nhiu protein dng si nh keratin lng, sng, mng.

    Lin kt hydrogen gi v tr c bit quan trng trong tnh c ng, linh hot ca cc phn t sinh hc, ca protein cng nh m bo. Chnh cu trc bc hai lm cho phn t protein mm do c th n hi c.

  • Mc d cu trc protein c cng c rt nhiu bng lin kt hydrogen, nhng cc th nghim v ho l cho thy rng cu to vng xon c trong dung dch khng bn v s b bung ra thnh chui ni. iu ny a n vic ra cu trc bc ba vi nhiu loi lin kt c tc dng n nh ng k nhng mi xen protein dng cu.

    2.2.2.3. Cu trc bc ba ca protein - lin kt disulfid (-S - S-)

    Cu trc bc ba l dng khng gian ca cu trc bc hai, lm cho phn t protein c hnh dng gn hn trong khng gian. S thu gn nh vy gip cho phn t protein n nh trong mi trng sng.

    C s ca cu trc bc ba l lin kt disulfid. Lin kt c hnh thnh t hai phn t cystein nm xa nhau trn mch peptid nhng gn nhau trong cu trc khng gian do s cun li ca mch oevtid. y l lin kt ng ho tr nn rt bn vng.

    Cu trc bc 3 to nn trung tm hot ng ca phn ln cc loi enzym. S

    thay i cu trc bc ba dn n s thay i hng xc tc ca enzym hoc mt kh nng xc tc hon ton.

    Ngoi trn kt disulfit, cu trc bc ba cn c n nh (bn vng) nh mt s lin kt khc nh:

    - Lin kt hydro: hen. kt ny xut hin khi gia hai nhm tch in m c nguyn t hydro.

    Lin kt tn: lin kt ny hnh thnh gia hai con tri du ca hai gc acid amin nm xa nhau theo th t trong chui peptid, nhng gn nhau trong cu trc khng gian. V d: gia COO- ca acid glutamic vi NH3+ ca lysin. Loi lin kt ny nm ri rc trong phn t do c mt s gc acid amin c hai nhm COOH v NH2.

  • V d v cu trc bc 3 nh: Phn t insulin l mt polypeptid bao gm 51 acid amin chui A c 21 gc acid amin v chui B c 30 gc acid amin. Hai chui ni vi nhau bi 2 cu disulfid: cu th nht gia gc cystein v tr 20 ca chui A v v tr 19 ca chui B; cu th hai gia gc cystein v tr th 7 ca c 2 chui. Trong chui A cn c mt cu disulfit gia 2 gc cystein v tr th 6 v 11 . Insulin l hon non tuyn tu tham gia iu ho hm lng ng trong mu. Khi thiu insulin, hm lng ng trong mu tng cao, dn ti hin tng bnh i ng Insulin c tc dng h ng huyt bng cch xc tin qu trnh tng hp glycogen d tr t glucose.

  • - Lc hp dn Van dt Vals: l lc ht gia hai cht hoc hai nhm ho hc nm cnh nhau khong cch 1 - 2 ln ng knh phn t.

    Lc lin kt ca cc nhm k nc, nhng nhm khng phn cc (- CH2; -CH3) trong vang, leucin, isoleucin, phenylalanin... Nc trong t bo y cc gc ny li vi nhau, gia chng xy ra cc lc ht tng h v to thnh cc bi k nc trong phn t protein.

    Do c cu trc bc ba m cc protein c c hnh th c trng . v . ph hp vi chc nng ca chng. cc protein chc nng nh enzym v cc khng th, protein ca h thng ng mu... thng qua cu trc bc ba m hnh thnh c cc trung tm hot ng l ni thc hin cc chc nng ca protein.

    S duy t hnh dng gip protein trng thi nguyn vn, tc l cc hot tnh sinh hc c duy tr. Mi bin i ca hnh dng ko theo s bin i ca hot tnh.

    men cu trc (Structural domain) c nghin cu t 1976, n nay ngi ta cho rng s hnh thnh men rt ph bin cc chui peptid tng i di.

    men cu trc c th c nh ngha l nhng b phn, nhng khu vc trong mt phn t protein c cun gp trong khng gian ging nh mt phn t protein nh hon chnh v thng l nhng ni thc hin chc nng lin kt, chc nng lp rp ca phn t protein trong hot ng chc nng ca n. Trong nhiu protein, men gn lin vi chc nng kt hp c hiu v nhiu enzym c cu to t cc men th trung tm hot ng li c b tr bin gii ca hai hay nhiu men.

    S thnh thnh cc men trong phn t protein to ra kh nng tng tc linh hot gia cc i phn t, kh nng c ng, dch chuyn tng ng gia nhng b phn trong qu trnh thc hin chc nng sinh hc. - nhng protein ngun gc khc nhau, nhng c chc nng tng t th cc men c cu trc tng i ging nhau.

    2.2.2.4. Cu trc bc bn ca protein

    L mt trng thi t hp hnh thnh t nhiu tiu phn protein c cu trc bc ba hon chnh.

    Mt s protein c xu hng kt hp li vi nhau thnh nhng phc hp, thnh nhng i phn t, khng ko theo s bin i v hot tnh sinh hc.

    Rt nhiu trng hp protein phi t hp li mi c hot tnh sinh hc. Trong nhng trng hp ny, cu trc bc bn l iu kin hnh thnh nn tnh nng mi ca protein.

    V d v cu trc bc bn:

    - Hemoglobin (Huyt sc t) gm 4 tiu phn protein: hai tiu phn v hai tiu phn . Nu 4 tiu phn tch ri nhau th mi tiu phn khng th vn chuyn c mt phn t O2' Khi kt hp li thnh trng thi tetramer to thnh mt khi khng

  • gian c

    th gn nh hnh t din th mi c kh nng kt hp v vn chuyn kh oxy. Mt phn t hemoglobin (Ht) vn chuyn c 4 phn t oxy.

    - Enzym glycogen phosphorylase ( c, gan) xc tc qu trnh phn gii

    glycogen thnh glucose.

    + trng thi khng hot ng enzym ny dng "b" (dng hai dimer tch ri nhau).

    + trng thi hot ng (khi c tn hiu cn ng) hai dimer t hp li thnh tetramer (dng "a").

    Khi nhu cu gii phng glucose gim, tetramer li tch thnh hai dimer, enzym tr li dng khng hot ng.

    Tu theo protein m s lng monomer c th thay i t 2,4,6,8 l ph bin, c bit c th ln ti trn 50 monomer.

    S hnh thnh cu trc bc bn to iu kin cho qu trnh iu tit sinh hc thm tinh vi, chnh xc.

    2.3. CC C TNH CA PROTEIN

    2.3.1 Trng lng phn t

    Ngay phn nh ngha nhn mnh: c im ca protein l trng lng phn t rt cao. Nhng nghin cu khc nhau gn y cho thy trng lng phn t thc ca protein nm trong khong 6.000 - 12.000. Tuy nhin, trong iu kin t nhin phn t protein thng lin kt vi nhau to thnh nhng phn (gi l mixen) c trng lng phn t rt ln t ti hng triu.

    Trng lng phn t ca mt s loi protein:

    Albumin sa 17.400

    Albumin trng 44.000

  • Globulin huyt thanh 310.000

    Hemoglobin ngi 68.000 Enzym pepsin 45.000 Enzym ribonuclease 12.700 Siu vi khun cm 322.000.000

    C th ni: protein l "i phn t" bi v thnh phn ca n gm hng trm, hng nghn nguyn t lin kt vi nhau ch yu bng lin kt ng ho tr.

    2. 3.2. Trng thi keo

    u th k XIX cc nh khoa hc bn ci kh lu v trng thi nguyn sinh cht (protoplasma) sinh th, bi v c nhng mu thun: * C th nguyn sinh cht l trng thi lng. Bi v ti sao cc phn ng ho hc tin hnh trong c th vi tc nhanh? iu ny c trng cho mi trng lng. * Nhng ti sao c th li c kh nng gi nhng hnh th c bit ca mnh? Tnh cht ny ch c th rn. Mi mu thun c gii thch khi ngi ta pht hin ra trng thi keo ca protein.

    Trng thi keo ca protein th hin cc c im sau: - Gy p sut thm thu rt thp 30 - 40mm Hg (0,03 tm) - Kh nng khuch tn t - nht cao.

    nht phn nh cu trc (hnh dng, kch thc) ca phn t - Kch thc cng ln nht cng cao.

    Nu ly nht ca nc lm chun l 1 th: nht ca albumin trng g l 1,2 - 1,57 nht ca gelatin l 4,54 - 14,2

    - Kh nng hp ph cc cht khc kh cao - Kh nng khuch tn nh sng (hin tng Tindal) tc l khi cho 1 tia sng qua dung dch protein trn nn c ca dung dch ta nhn r c nhng tia .

    2.3.3. Lng tnh v im ng in

    2.3.3.1. Tnh tng tnh Trong dung dch nc, phn t protein c kh nng tc ng nh mt acid, hoc mt kim yu, bi v trong phn t protein c cc nhm nh chc qun v carboxyl c kh nng phn ly.

    Phn t protein mang c in tch dng v in tch m nh vy gi l amphiol.

  • Kh nng phn ly ca nhm quan v nhm carboxyl thay i ph thuc vo iu

    kin mi trng, c th l pa. Khi pH thp, ion H+ mi trng nhiu th nhm COOH gim s phn ly. Ngc li, nu mi trng kim, tc ton OH nhiu th NH2 s bt phn ly.

    V s lng nhm quan v carboxyl trong phn t protein khc nhau, cho nn nu s lng nhm COOH tri hn nhm NH2 th sau khi phn ly, in tch tng s ca ht keo protein s c du m v ngc li.

    Khi cho dng in mt chiu i qua mi trng th nhng ht keo ni trn s

    di chuyn v in cc tng ng.

    Tu i lng in tch, tu trng lng phn t m tc di chuyn ca mi loi protein khc nhau. l c s ca phng php in di trn giy.

    2.3.3.2. im ng in

    Nh chng ta bit, kh nng phn ly ca cc nhm quan v carboxyl chu s chi phi ca phn ng mi trng, do bng cch thm acid hoc kim ta c th t ti mt tr s pa, m s phn ly ca NH2 v coh bng nhau. pH ny ngi ta gi l im ng in ca protein (k hiu l pI).

    Ti im ng in cc ht keo c in tch bng O

    Mt vi v d v im ng in ca protein:

    Casein 4,7 Zein ng 6,2

    Albumin 4,8 Miosin c 5,0

    Globulin 5,4 Histon 8,5

    C th da vo im ng in tch ring tng loi protein.

    2.3.4. c tnh ho tan

    Trng thi keo ca protein bn vng l nh c lp v thu ho bao bc bn ngoi cc ht keo v cc in tch lm cho cc phn t protein ngn cch v khng dnh vo

  • nhau. C nhiu yu t nh hng n tnh tan ca protein.

    - nh hng ca pH

    tan ca protein thp nht pH = pI ca n, tan ca protein tng ln khi pH nm xa i v khi pH = pI th phn t protein khng tch in nn chng khng c lc y

    tnh in v d b ng kt. Khi pH khc i th cc phn t protein tch in cng du v y nhau cho nn khng b ng kt, do tan tng ln.

    - nh hng ca nng mui

    Mui trung tnh nng thp lm tng tan ca nhiu loi protein. Khi tng nng mui ti mt gii hn nht nh th tan ca protein gim xung v nu nng mui tip tc tng ln th protein c th ng kt hon ton. Tnh cht ny c ng dng tch cc loi protein theo phng php dim tch.

    - nh hng ca dung mi

    Khi cho cc dung mi nh cn, e, benzen, aceton, cloroform... vo dung dch protein th tan ca protein b gim v c th dn n ng kt do ph v lp v thy ha.

    - nh hng ca nhit

    Trong khong nhit t 0 n 450C, tan ca protein tng khi nhit tng. Cn khong nhit t 45 - 750C a s protein mt tnh keo v c th b bin tnh (tr protein ca mt s loi sinh vt chu nhit).

    2.3.5. Hin tng sa lng v bin tnh

    Trng thi keo ca protein bn vng l nh s cn bng cc in tch v lp v thu ho. Khi trng thi ny b ph v bi cc yu t nh nhit cao, mui cc kim loi nng, dung mi hu c... th protein rt d b sa lng. Hin tng sa lng protein c th thun nghch, tc l n c th tr li trng thi ban u khi tc ng ca cc yu t trn cha tht su sc. Tuy nhin, nu s tc ng mnh v lu s lm cho protein b bin tnh. Khi b bin tnh protein s mt hot tnh sinh hc ca n.

    2.4. PHN LOI PROTEIN

    Cha c mt cch phn loi no phn nh tt nht bn cht v s lng ca nhm cht hu c quan trng ny.

    Ngy nay, ngi ta c th phn loi protein theo cc s c sau y:

    2.4.1. Da vo hnh dng ca protein

    Da v hnh dng ca protein ngi ta tm phn hnh th protein thnh hai dng: dng cu v dng si.

    2.4.1.1. Protein dng cu

  • Protein dng cu l loi protein m phn t ca n thng cun li thnh vng, thnh bi, gn trn hoc bu dc.

    in hnh ca dng protein ny l: Albumin, globulin trong, sa, huyt thanh, enzym pepsin, dch v. . . Loi ny thng ho tan trong nc .

    Tuy gi l dng cu, nhng nu xt t l ng knh ca chng ta thy tng ng l/3 ( glubulin sa) 1/7,5 (ca globulin huyt thanh) 1/20 (ca zein ng). V vy l nhng cu hnh a phnh th ng hn.

    2.4.1.2. Protein dng si

    Protein loi ny vi mch peptid khng cun r, ch gp np dc chui, nn ni chung c chiu di r rt.

    in hnh ca dng protein ny l: fibroin t tm, miosin si c, colagen v elastin da v gn. c tnh ca loi ny l khng ho tan trong nc v c kh nng co gin mt chng mc no , v nhng np gp ca chui peptid c th bin i theo trc di.

    V d protein dng si nh a v Keratin

    4.2. Da vo chc nng ca protein

    - Protein co gin c (actin, miosin ca c)

    - Protein d tr (Femtin gan d tr st)

    - Protein men trao i cht (Pepsin d dy thu phn protein)

    - Protein hormon (Insulin, vasopressin)

  • - Protein khng th

    - Protein c t

    - Protein c chc nng c bit (Hemoglobin mang oxygen, rodopsin trong qu trnh th gic, virus).

    2.4.3. Da vo gi tr dinh dng ca protein

    Cc nh sinh vt hc li da vo gi tr dinh dng hay tm quan trng ca protein i vi s sng phn loi protein. Theo quan im ny protein chia lm 2 loi:

    2.4.3.1. Protein c gi tr dinh dng khng hon ton

    l nhng protein cha khng y hoc y nhng t l khng cn i cc acid amin thit yu. Loi ny thng l cc protein thc vt.

    2.4.3.2. Protein c gi tr dinh dng hon ton

    l nhng protein cha y vi t l cn i cc acid amin thit yu. Loi ny thng l cc protein ng vt nh trng, sa, tht...

    2.4.4. Da vo cu to ho hc ca protein

    Theo quan im ca Hp-pe-zai-l (Hoppe - Seyler) v Drecxen ra gia th k XIX protein chia lm 2 lp ln:

    - Lp protein n gin hay ng nht

    - Lp protein phc tp hay cn gi l proteid

    2.4.4.1 . Lp protem n gin

    y l nhng protein khi b thu phn hon ton s cho ta cc acid amin.

    Cc i din chnh ca lp ny l:

    * Albumin v globulin

    L hai loi protein dng cu rt ph bin trong cu to ca m bo ng vt v thc vt Thnh phn gm hon ton cc acid amin trong t l acid amin c tnh acid kh cao.

    Albumin l protein n gin ph bin nht. N tm thy trong mu, dch t bo, dch tu sng. Albumin ho tan trong nc v cc dung dch mui. Albumin ng khi un nhng cc nhit khc nhau: albumin trng ng nhit 560C, albumin huyt thanh 670C, albumin sa 720C.

    Albumin ca ng vt (nh albumin huyt thanh ca mu) khi thu phn cho 19 acid amin v thnh phn cc acid amin t khc nhau cc ng vt (tr vt). Albumin thng cha s lng ln cc acid amin sau: leucin, acid glutamic, acid aspartic, ly sin, cn cc acid amin nh methionin, tryptophan, glycocol... s lng t hn.

  • Trng lng phn t ca albumin khong 35.000 - 70.000, im ng in nm trong khong pH 4,6-4,7.

    Albumin thng to thnh cc phc cht vi lipid, acid bo, Acid amin, khng th...nn c quan im cho rng n gi vai tr tch cc trong trao i vt cht.

    Globulin hu nh nm cng vi albumin v rt ph bin trong t nhin. N c nhiu trong mu ng vt, trong cc c quan, t bo, trong cc dch lng ca c th.

    Globulin kh tan hoc hon ton khng tan trong nc, nhng tan trong cc dung dch ca mui trung tnh, kim, acid.

    Globulin cha khong 14-19 acid amin quan trng nh: leucin, vang, ly sin, acid glutamic, sm, treo nin.

    Trng lng phn t ca globulin khong 90.000 - 1.500.000 hoc ln hn, im ng in nm trong khong pH 5,0-7,5.

    Globulin gm , , . Chnh y - globulin l ngun gc khng th trong c th.

    T l AIG trong huyt thanh ng vt thng mc kh n nh v thay i r khi c th mc bnh. iu c ngha rt ln trong chn on v tnh trng sc kho ca ng vt ng thi hm lng globulin huyt thanh cn phn nh tnh khng ca c th.

    * Hisum v protamin

    Histon v protamin l hai loi protein c tnh kim r rt v trong thnh phn ca chng t 30 - 80% acid amin kim tnh nh ly sin v arginin.

    Histon l protein c cu to n gin. N cha s lng aci quan t hn so vi albumin v globulin. Trong histon khng c cystein, cystin, tryptophan, m ch yu l arginin v ly sin (20-30%). Histon c Koccel tm thy trong nhn t bo, trong thnh phn ca nucleoprotein v cc protein phc tp khc. im ng in ca histon nm trong khong pH 9,0-11,0.

    Protamin c Miser v Koccel tm thy trong thnh phn ca nucleoprotein ca t bo sinh dc c. Sau cn pht hin lch, tuyn diu v cc c quan khc. Protamin c trng lng phn t thp (2.000-8.000), thnh phn cha t acid amin (6-8), trong ch yu l acid amin diamin (ti 80% arginin). i din protamin c nghin cu nhiu l xan min- l mt chui polypeptid kt thc bi nhm quan ca thon. Khi un protamin khng ng v khng sa lng, n ch sa lng bi mui kim loi nng. im ng in ca protamin nm trong khong pH t 10,5 n 12,0.

    * Glutelin v prolamin

    l nhng protein thc vt c trong cht do ca la, go, ng.

    - Prolamin c nhiu cc ht ho tho. c im ca prolamin l tnh ho tan trong cn 70% v khng tan trong nc. Khi thu phn prolamin thng cho nhiu

  • thon v acid glutamic (43%).

    My i din ca prolamin c nghin cu k nht l gliadin ca la m, gordein ca i mch, zein ca ng, avenin ca yn mch, n~enin ca go... Trong thnh phn my protein ny t l lysin rt thp ( zein hu nh khng c).

    - Glutelin c cc loi ht khc nhau, hm lng t t 1 - 3%, c tnh ca glutelin l ch ho tan trong kim long 0,2 - 2,0%.

    * Cc proteinoit

    y l nhm protein ca m chng c th ng vt nh xng, gn, da, sng, lng, mng... Chng c gi l "ging protein" v tuy c cu to t cc acid amin, nhng chng mt tnh keo quan trng l tnh ho tan. y l nhng git'.in bin tnh, c dng si gp nm song song thnh b.

    Chc nng: bo v c gii i vi m bo.

    Cc i din ca nhm ny l:

    Colagen (v procolagen) l protein ca si m lin kt gn, da, di da... N khng ho tan trong nc, nhng khi tc ng lu ca nhit s tr thnh dng ho tan l gelatin. Keo dn ch da tru chnh l colagen.

    Hm lng glycin ca colagen kh cao (25%), nhng v nhiu acid amin khng thay th c th li thiu.

    Colagen tng t l vi tui tc.

    - Elastin: phn b cc m co gin v chu lc nh gn, dy chng cc khp xng.

    bn chc ca elastin cao hn colagen v hon ton khng th trng nh colagen.

    - Keratin (ting Hy Lp keras - sng)

    L cht ch yu ca tc, lng, sng, mng, lp thng b... hon ton khng tan, k c trong dung dch acid, kim. Khi thu phn cho nhiu cystin (7 - 12%) v acid glutamic (4 - 17%).

    Trng lng phn t khong 2 triu.

    Fibroin: protein ca t la do tm nh ra.

    Si t do nhiu si fibroin lin kt thnh b, gn bi h sericin ca tm hoc nhn nh ra (m t vi nc nng nhm ty h ny).

    2.4.4.2. Lp protein phc tp

    Lp protein phc tp, hoc protein khng ng nht, l nhng cht bao gm 2 thnh phn:

  • - Phn protein n gin

    - Phn ph hay cn gi l nhm ghp.

    Nhm ghp c ngun gc khc nhau. S lin kt gia chng vi phn protein n gin c bn vng khng u, c cht lin kt cht ch, c cht lin kt hi ht, d tch trong qu trnh. phn tch nghin cu.

    Da vo bn cht ca nhm ghp, ngy nay ngi ta chia protein phc tp thnh 5 loi chnh.

    - Glucoprotein

    - Phosphoprotein

    - Chromoprotein

    - Lipoprtein

    - Nucleoprotein

    2.5. CC LOI PROTEIN PHC TP

    Nh trn trnh by, protein phc tp l loi protein khi thu phn ngoi phn protein n gin, cn c thm nhm ghp. Ph thuc vo nhm ghp m protein phc tp c tn gi tng ng. Sau y ta xt tng loi:

    2.5.1. Glucoprotein

    Nhm ghp ca loi ny l nhng dn xut ca glucid, c th di dng quan ho nh glucosamin, galactosamin, manosamin chng lin kt vi phn protein bng nhng lin kt ng ho tr.

    Glucoprotein c vai tr quan trng trong cu to ca nhiu loi m chng v bo v v d trong sn xng, trong cu to ca khng nguyn v khng th.

    Glucoprotein hay gp trong c th ng vt thng chia lm hai loi:

    * Mucin: l nhng cht thng c nhiu trong nc bt, nc mt, dch nhn bao khp, dch m lin kt, dch nang bo, nim dch. Mucin nim mc d dy, rut, niu qun c tc dng bo v c gii v ho hc. Nhm ghp ca mucin l hp cht acid

    Tc dng ca mucin l lm gim cc ma st c hc nhm bo v cc c quan

  • (nh nim mc ming, thc qun, d dy...).

    * Mucoid: c nhiu m bo nh:

    - sn c chondromucoid

    - xng c osteomucoid

    - lng trng trng c ovomucoid

    v nhiu cht na gn, gic mc mt, thu tinh th...

    Ngoi ra mt s glucoprotein c chc nng sinh hc quan trng nh hon non kch thch tuyn sinh dc: FSH, prolanA cha 20% glucid, LH cha hn 20% glucid.

    Trn mng t bo c nhng cu trc min dch c th ca mi c th sinh vt c bn cht l glucoproteid. 1

    2.5.2. Phosphoprotein

    L protein phc tp khi thu phn cho cc acid amin v acid phosphoric (H3PO4) cc aci phosphoric ni vi protein bng mch este qua nhm OH ca serin hoc treonin trong phn t protein.

    Loi protein ny thng c tnh toan v ng vai tr quan trng trong dinh

    dng ca ng vt non.

    i din in hnh c th k l:

    - Casein: l protein ch yu ca sa.

    - Ovovitelin v vinh lng trng

    - Ictulin trng c.

    Thnh phn ca cc loi ny cha y 20 loi acid amin v rt cn i nn t l hp th kh cao v l nhng loi thc n c gi tr dinh dng c bit.

    2.5.3. Chromoprotein (ch Hy Lp: Chroma - mu sc)

    y l nhng protein mang mu sc nh hemoglobin trong mu c mu , clorofil trong l cy c mu xanh...

    S d c mu v nhm ghp ca chromprotein thng l nhng cu trc phc tp, to nn cc mu sc khc nhau do c cha mt hay nhiu nguyn t kim loi nh Fe, Mg, Cu...

  • Phn nhiu chromoprotein tham gia vo cc qu trnh trao i kh

    V d: Hemoglobin vn chuyn O2 v CO2 gia phi v m bo

    Mioglobin d tr O2 cho c.

    Catalase phn gii H2O2 thanh O2 V H2O.

    Mt s i din chnh ca nhm ny l:

    2.5.3.1. Hemoglobm (cn gi l huyt sc t, k hiu l Hb)

    Hemoglobin c Huyn-ne-phan tm ra 1840. l loi protein c nhiu trong hng cu, thnh phn ca n gm:

    - Phn protein n gin l globin chim 94% trng lng Hb

    - Phn nhm ghp l nhn Hm chim 6%

    Trng lng phn t ca Hb gn 67.000. Chc nng ca Hb l vn chuyn kh gia phi v m bo

    * Cu to

    Hemoglobin c cu to t protein - globin v nhm ghp l hm. Cu to ca hm c Nenski v Fisher tin ra.

    Cu trc hem ca hemoglobin: Hem l lin kt, m phn t ca n gm nguyn

    t t 2 v 4 vng pyrol. Bn vng pyrol ni vi nhau bng dy metyl (= CH- ) - l ct porfin. Ct porfm gn vi 2 gc Vinyl (- CH = CH2) 4 gc metyl (- CH3) v 2 gc acid ropionic to thnh dng protoporfl. Protoporfin lin kt vi st 2 chnh l nhn hm (hnh trn).

  • Ngoi ho tr chnh ra, st cn ni vi 2 nguyn t Nit bng hai lin kt ph (biu din bng ng chm).

    Mi phn t hemoglobin c 4 tiu phn protein: hai tiu phn v 2 tiu phn . Mi tiu phn gn vi mt hm. Nh vy phn t hemoglobin c 4 hem. Cch lin kt gia hm v globin cha c xc nh r. Theo nhiu ti liu ca nhiu tc gi th lin kt ny xut hin gia st v nh ca nhn imidazol ca phn t histidin trong globin.

    * Tnh cht ca hemoglobin v cc dn xut ca n

    Khi tc ng vi acid hoc kim, hm - st hai s thnh hm - st ba: Fe2+ Fe3+ v c tn l hematin.

    Chc nng sinh l ca hemoglobin th hin tnh lin kt vi cc loi kh nh O2, CO, NO... Tu p lc ring ca chng, s lin kt ny thc hin qua mch ph ca nguyn t st vi globin nn khng bn v cc kh s d y nhau tu p sut mi loi. C my lin kt v dn sut ca hemoglobin l:

    - Oxyhemoglobin Hb.O2 (vi oxy)

    - Carboxyhemoglobin Hb.Co (vi oxyt carbon)

    - Met-hemoglobin Hb.OH (khi Hb b oxy ho thnh dng ferric)

    + t bo phi: p sut ring ca oxy cao nn n d lin kt vi hm. y l

    lin kt h, nguyn t st 2 khng thay i ho tr, nn khng phi l phn ng oxy - ho. Hb.O2 to cho mu c mu ti.

    Khi ti mch qun cc m, p sut ring ca oxy thp nn kh ny thot ra v c dng vo cc nhu cu sinh ho hc.

    + m bo: CO2 (khong 20% tng s CO2 thi ra) s lin kt vi globin qua nhm quan cui cng thnh carboxyhemoglobin.

    Phn ch yu (gn 80%) CO2 lin kt vi kim ca huyt tng v hng cu thnh nhng bicarbonat nh NaHCO3, KHCO3 ri mi n phi, chuyn sang dng acid carbonic v thi theo hi th.

    Khi trong khng kh c gn 1% th tch Co th gn 95% Hb ho thnh Hb.Co v vy vic ly O2 b tr ngi lm cho c th b ngt. Nu tng p sut ring ca oxy (cho th oxy) th Co b y khi Hb v cha c ngt.

    Khi Hb b tc ng bi cht oxy ho nh femxyanua kim (K3[Fe (CN~ oxyt no th Hb Hb.OH c st ba.

  • Nu HbOH sinh nhiu, chc nng h hp ca mu s b tr ngi. lu Hb.OH

    b phn ly tr Hb v dng c.

    l c s gii c HCN (cht ny bin Hb thnh cyanomet - hemoglobin) bng xanh metylen (chuyn Hb.CN kh phn ly sang dng Hb.OH d phn ly).

    Tng quan gia hemoglobin v cc dn sut ca n nh oxyhemoglobin, carboxyhemoglobin v methemoglobin c th biu din nh sau:

    2.5.3.2. Mioglobin

    Mioglobin l sc t ca c, cng c nhm ghp l hm cha st nh hemoglobin.

    Nhm globin ca mioglobin c trng theo loi, trng lng phn t trung bnh 17.000.

    Khc vi hemoglobin, nhm ghp ca mioglobin ch cha mt nguyn t st, v vy m phn t protein ca n ch c mt nhn hm. Tuy c cu to n gin hn hemoglobin nhng i lc ca n i vi oxy mnh hn hemoglobin.

    c nht l c tim, vai tr d tr oxy ca mioglobin (di dng oxymioglobin) rt quan trng: hin tng ny m bo cho c hot ng khi b i O2 trong trng hp s np O2 b gin on tm thi (nn th, ngp ln...)

    V d: ngi, c th d tr 2450ml O2 trong 354ml c trong mioglobin.

    Lng d tr ny rt ln nhng ng vt sng nc nh Hi Cu.

    Mu ca c do mioglobin to nn.

    2.5.4. Lipoprotein

    Lipoprotein l lin kt gm nhiu phc cht ca protein v lipid. bn ca mi lin kt protein - lipid khng c nh.

    Lipoprotein c tnh ho tan trong nc, nhng khng ho tan trong cc dung mi hu c (nh e, cloroform...)

    Chc nng sinh hc ca nhm ny gm nhiu mt, nhng quan trng nht l chc nng cu to vch t bo v cu to cc tiu kh quan t bo nh ty lp th.

  • Ngi ta cho rng tnh bn thm v tnh hp th c hiu ca t bo l do lp v lipoprotein quyt nh.

    Trong mu v m bo c my cht hpoprotein quan trng nh:

    Tromboplastin (gip cho qu trnh ng mu)

    Lipoprotein huyt thanh (c phn protein l globin)

    - Rodopsin vng mc mt l loi lipoprotein tham gia vo hot ng th gic.

    - Ni c t ca nhiu vi khun cng c cu trc l lipoprotein. V d: ni c t ca vi khun lao, brucena...

    2.5.5. Nucleoprotein

    y l loi hp cht hu c c mt vai tr cc k quan trng trong sinh hc. Ngi ta tm thy chng nhng sinh vt n gin nht (nh nguyn sinh ng vt) n nhng ng vt cao ng nht (nh loi c v). Ngay cc siu vi khun (vus) cng c thnh phn ch yu l cc nucleoprotein. Qua cc nghin cu v di truyn hc, t chc hc, sinh ho hc ngi ta c th ni chc chn rng: Nucleoprotein c quan h trc tip n cc qu trnh sng ch yu ca mi sinh vt nh tnh di truyn, bin d, kh nng tng hp protein.

    Nucleoprotein gm 2 thnh phn ch yu:

    - Protein n gin (thng l protein kim tnh nh protamin v histon) - Nhm ghp l acid nucleic.

    Do tm quan trng ca lp nucleoprotein i vi s sng nn chng ta s nghin cu t m chng mt chng ring.

  • Chng 3

    NUCLEOPROTEIN V ACID NUCLEIC

    3.1. I CNG V NUCLEOPROTEIN

    Nucleoprotein l protein phc tp gm hai thnh phn ch yu l:

    - Phn protein n gin thng l protein kim tnh nh protamin v histon.

    - Phn nhm ghp l acid nucleic

    Phn protein n gin ta xt chng 2, y ch yu ta nghin cu v acid nucleic

    S thu phn nucleoprotein c th biu hin nh sau:

    Nucleoprotein c pht hin ln u tin nm 1869 o Mischer trong cc t bo

    m.

    Cng lao cc nh bc hc: Le vin, Chagaff, Devison,Watson, Cch... lm sng t thnh phn cu to ca acid nucleic.

    3.2. THNH PHN V CU TO ACID NUCLEIC

    Acid nucleic khi thu phn hon ton th phn thnh ba loi hp cht:

    - Cc ng pentose: D-ribose v D-desoxyribose

    - Cc baz: phun (adenin, guanin) v pyrimidin (Cytosin, uracin, thi min)

  • - Gc acid phosphonc (H3PO4)

    3.2.1. ng pentose

    Pentose gm D- ribose v D - desoxynbose. Hai cht ny c trong acid nucleic di dng Phu ran :

    Ribose c trong acid ribonucleic (ARN)

    Desoxyribose c trong acid desoxyribonucleic (ADN) 3.2.2. Cc baz

    3.2.2.1. Bazpynmidin

  • 3.2.2.2. Bazpurin

    3.2.3. Nucleosid

    Nucleosid l kt qu ca s kt hp bng lin kt osid gia mt baz (phn hoc pyrimidin) v mt ng pentose vi s loi ra mt phn t nc.

    S lin kt ny thng qua mch glyosid v tr 9 ca phn hoc v tr th 3 ca

  • pyrimidin.

    V d:

    Nucleosid c nhn pyrimidin mang tn tn cng bng - mn Nucleosid c nhn

    phn mang tn tn cng bng - o sin Cc nucleosid ca cc baz c tn nh sau:

    3.2.4. Nucleotid

    Nucleotid l nhng este ca nucleosid vi acid phosphoric. Nucleotid l n v c bn ca acid ~lucleic - n nh cc mt xch ca si xch.

    Nhiu mnonucleotid ngng t vi nhau thnh polynucleotid (hay l acid

    nucleic).

    Trong phn t acid nucleic, s este xy ra v tr 3' hoc 5'.

    V d: cu trc ca mononucleotid c tn l acid adenilic (tc l adenosin - 5 phosphatl.

  • Acid phosphoric thng c gn vo v tr th 3 hoc th 5 ca ng pentose.

    Loi gn v tr th 3 thng dng lin kt, cn v tr th 5 thng dng t do.

    Sau y l tn gi ca cc nucleotid

    Baz Nucleotid trong ARN Nucleotid trong ADN K hiu

    Adenin Acid adenilic Acid desoxyadenilic A

    Guanin Acid guanidilic Acid desoxyguanidilic G

    Urasin Acid uridilic Acid desoxyuridilic U

    Cytosin Acid cytidilic Acid desoxycytidilic C

    Thimin Acid thimidilic Acid desoxythimidilic T

    Cch lin kt ca cc mnonucleotid nh sau:

    Cc nucleotid c th phosphoryl-ho to thnh di-, tri- phosphonucleotid.

    Dng ny thng trng thi t do trong cc m bo v c quan ca sinh vt v lm nhim v d tr nng lng do thu c trong qu trnh oxy ho cung cp cho cc hot ng sng - cu trc ca chng nh sau:

  • Nh vy ta thy trong chui polynucleotid, ng v phosphat lin kt vi nhau,

    cn gc kim nm t do, chnh s lng v th t phn b ca cc gc kim trong chui nolvnucleotit quyt nh tnh c trng sinh hc ca phn t acid nucleic.

    3.3. PHN LOI ACID NUCLEIC

    3.3.1. C s phn loi acid nucleic

    Da vo s c mt ca ng ribose v desoxyribose m ngi ta chia acid nucleic ra lm hai lp.

    - Acid ribonucleic (ARN)

    - Acid desoxyribonucleic (ADN)

    Khi nghin cu v hai lp ARN v ADN ngi ta thy chng c mt s im khc bit nh sau:

    ARN - Ch yu t bo cht - Trng lng phn t 2 - 3.104 - 6 - cu to Chui n - Cha cc gc kim

    Adenin (A) Guanin (G) Cytosin (C) Uracin (U)

    - ng: Ribose - Chc nng sinh hc: trc tip tham gia

    qu trnh tng hp protein.

    ADN - Ch yu nhn t bo - Trng lng phn t: 1 - 2.106 8 - cu

    to Chui kp - Cha cc gc kim Adenin (A) Guanin (G) Cytosin (C) Thi min (T) ng Desoxyribose Chc nng sinh hc: mang bn mt m

    di truyn.

    3.3.2. Tn gs ARN, ADN v lin kt ho hc

  • Thnh phn ho hc ca ARN v ADN

    Acid nucleic l cht trng hp ca mononucleotid. Phn t cha t 250 - 350

    nucleotid, c loi cha ti hng chc vn mononucleotid. Cc mononucleotid ni vi nhau qua mch lin kt este gia hydroxyl ca carbon th 3 ca ng pentose vi acid phosphoric ca mononuleotid bn cnh.

    Acid nucleic ng vai tr trong di truyn ca ng v thc vt, n ng vai tr

    ch cht trong vic sinh tng hp protein.

    Sau y chng ta s i su nghin cu tng loi acid nucleic

    3.3.3. Acid desoxyribonucleic (ADN)

    Da vo s liu nghin cu hin tng nhiu x tia Rn-ghen v nhng s liu ho l khc ngi ta i n kt lun rng ARN ch c cu trc chui n, cn ADN c cu trc chui kp (tc l do hai chui polynuleotid kt hp vi nhau theo kiu xon thng).

    3.3.3.1. Quy lut b sung gc kim (qui lut Chagaff)

    Khi phn tch nh tnh v nh lng ADN, Chagaff v cc cng s ca ng rt ra c kt lun sau:

    - Hm lng tnh theo mt ca Adenin bng Thi min v Guanin bng Cytosin.

    - T nhn xt (l) v (2) rt ra: tng s gc kim purin bng tng s gc kim

  • pyrimidin.

    A + G =T+C

    V mt ho hc: hm lng nhm 6 - quan bng hm lng nhm 6 - xe ton.

    T ba kt lun trn y Chagaff rt ra c qui lut b sung gc kim nh sau: Trong iu kin sinh l bnh thng, hai chui nucleotid khi to ra xon kp s lc n nh quanh nhau bng cc lc lin kt thng qua cc baz.

    - Trong qu trnh lin kt cc baz ca hai chui i din th mt chui s gp baz phun, chui kia s gp baz pyrimidin, cc baz lin kt vi nhau bng lin kt pydrogen, xut hin gia mt s v tr nht nh hai baz i xng, l v tr: Nl ca phn vi Nl ca pyrimidin

    C2 ca phn vi C2 ca pyrimidin

    C6 ca phn vi C6 ca pyridin

    - Lin kt hydrogen mun xut hin phi tho mn hai iu kin:

    + C mt nguyn t hydro mang in tch (+) nm gia hai nguyn t mang in tch (-).

    + Khong cch gia cc nguyn t mang in tch (-) nm trong khong 2 - 4 A0.

    Tc l lin kt hydrogen ch c th xut hin gia cc cp baz chn lc i xng:

    Adenin vi Thi min

    Guanin vi Cvtosin

    3.3.3.2. M hnh xon ADN

    Da trn cc kt qu nghin cu cho php Crick v Watson ra cu to m hnh xon ADN vo nm 1953. M hnh ny c kim tra li trn c s nhng th nghim v tia Rn-ghen tinh vi hn bi Willkins v cng s ca ng. Chnh v c nhng ng gp nn Crick, Watson v Wilkins c gii thng Nobel 1962.

    Theo Crick v Watson th ADN gm hai dy polynucleotid vi cc tri du nhau cun xon vi nhau xung quanh cng mt trc v to thnh vng xon i.

  • Cc baz nm trong vng xon thnh tng cp: pyrimidin trn mt dy v phn trn dy i xng v ngc li. Ch mt s cp baz nht nh ph hp: A i vi T; G i vi C (lin kt hydrogen).

    - Mi vng xon di 34 A0 cha 10 cp gc kim

    - di mt cp gc kim l 3,4 A0.

    - Bn knh vng xon 10A0

    - Khong cch gia hai gc kim i xng l 3A0

    3.3.3.3. Vai tr sinh hc ca ADN

    Ngy nay trong sinh hc, c bit l trong sinh ho hc v vi sinh hc, ngi ta thu c nhiu ti liu chng t rng ADN l c s cu trc ca nhim sc th mang tnh thng tin di truyn.

    Ngi ta thy ADN trong t bo thn ln gp i ADN t bo mm. Th t sp xp ca 4 gc kim trn polynucleotid c tc dng nh mt m di truyn. Khi cn ti to, mt dy nucleotid, dy xon i tch ra, lin kt hydro b t, mi dy nguyn thu c dng nh mt khun mu tng hp dy mi theo qui lut b sung gc kim.

    3.3.4. Acid ribonucleic (ARN)

    ARN c coi l cht tham gia trc tip vo cc phn ng tng hp protein. Loi ny thng tp trung t bo cht (ch yu bo tng) mt s nhn. Chng thng dng chui bi ch ri.

    ARN trong t bo chia lm 3 loi:

    3.3.4.1. ARN thng tin: K hiu m - ARN im - messenger - ngi a tin) Trng lng phn t ca loi ny t 0,5 - 1,106, chim 3 - 4% tng s ARN, chng c tng hp nhn t bo trn khun ca phn t ADN y l khun th cp.

    Nhim v ca m - ARN mang bn mt m di truyn hnh thnh nhn s chui qua mng nhn ra t bo cht v tin ti v tr tng hp protein ribosom, n s lm khun mu tng hp nn protein.

    3.3.4.2. ARN vn chuyn: K hiu t - ARN (t - transfer - vn chuyn)

  • t - ARN thng trng thi ho tan trong t bo, chim khong 15% tng s ARN.

    Trng lng phn t thp khong 2 - 3 vn, gm khong 60 - 100 nucleotit, gi chc nng vn chuyn acid amin hot ho t t bo cht n cc ribosom. Mt t - ARN ch vn chuyn c hiu mt acid amin tng ng vi n.

    Cu to: gm mt chui polynucleotit gp khc li ging nh hnh l c ba thy, c nhng on xon kp theo qui tc b sung gc kim: A-U; G-X.

    mt u chui c 3 gc kim t do, cc acid amin s c gn vo 3 gc kim c ch vo v tr tng hp protein ribosom.

    C 20 loi t - ARN tng ng vi 20 acid amin. Cc acid amin s kt hp vi t- ARN tng ng ca lum, to thnh tng lung i vo v tr tng hp protein m th t sp xp ca cc acid amin trong mch peptid th c m - ARN qui nh trc.

    3.3.4.3. ARN ribosom: K hiu r .ARN

    Trng lng phn t loi ny rt cao 1 - 2 triu, chim trn 80olo tng s ARN. Mt ribosom l mt ht nucleoproteid m phn acid nucleic l ARN. ng knh ca ribosom khong 200A0.

    S tp hp ca chng vi chc ngn i phn t s to thnh mt nh my vi m vng chc, c t chc hon ho, c kh nng c bn mt m di truyn trong mch m - ARN v thc hin thng tin dng mt phn t protein chun b sn v c cu trc c hiu.

    3.4. NUCLEOPROTEID

    3.4.1. Nucleohiston v nucleoprotamin

    ARN v ADN thng thy trong t nhin ( ng vt, thc vt cng nh vus) di dng kt hp vi protein.

    - Protein c bit quan trng l histon: tnh cht kim, trng lng phn t nh. Histon t do c cu trc xon a v hnh nh cu trc ny c duy tr trong nucleohiston.

    Gn y mt s tc gii chng minh rng ncleohiston chit sut t mm u cha ARN gn vi protein bng lin kt ng ho tr - Phc hp ARN - histon cha

  • 8% ARN v 92% protein.

    - Trong cc t bo sinh tinh trng thnh ca nhiu h c ADN c gn khng phi vi hislon, m vi protamin, protamin l protein c tnh kim mnh, cng nh histon, c t l arginin cao. Tuy nhin chng c kch thc khng ng u v nh hn, hnh nh chng c mang tnh cht c hiu chng loi.

    3.4.2. Nucleoprotid ca virus

    Vut l mt v d in hnh v cc loi nucleoproteid ng nht v t tr.

    Ba c im ca vus l: trong t bo dinh dng ca vt ch chng th hin s c mt ca chng qua cc hin tng sau :

    - T sinh sn

    - Gy hi chng bnh

    - Kh nng bin d

    Nh tnh cht th 3 m virus tr thnh nguyn liu qu nghin cu v di truyn.

    Nh vy kt hp cht ch vi vt ch m vus biu hin tt c mi c tnh ca s sng. Rt nhiu vus c tch ra tinh khit. Vut n gin nht v mt ho hc l gm c protein v acid nucleic. Protein c trong tt c mi vus (t 33 n 99%) bao bc xung quanh acid nucleic, lm nhim v che ch cho acid nucleic.

    3.4.2.1. Virut vi khun (thc khun bo)

    Thng rt ln, acid nucleic ca chng thng l ADN xon i u, nm trong mt ci "u' kt tinh nhiu mt i xng, gm nhiu n v nh protein rt ging nhau, c trng lng phn t 2.104. Thng chng c mt ci 'mui" d un ng lm c quan gn v chch. Ci ui ny c th gm nhiu thnh phn, chc phn v cu trc khc nhau nn s protein trong vus cng rt ln.

    3.4.2.2. Virut ng vt: C th cha ARN hoc ADN

    - Vut ARN thy bo tng, vus ADN trong nhn t bo ch, cc in hnh nh: + Vut gy bi lit v vus cocksackie l nhng nucleoproteit n gin a din, ging nh vus thc vt.

    + Vut gy vim no v vus gy cm cha ARN cng mt phn t lng nh, nhng phn t ca n a din v kh ln, v ngoi nucleoprotein cn c lipid v polysacant.

    + c bit nhm ng ch l reo virus c ARN vng xon i b sung vi trng lng phn t cao v gn ging ADN.

    Vut cha ADN: virus gy bnh mn rp (herpes), bnh u g, bnh quai b, si, thu u psitlacosis, di, polima...

  • Chng 4

    GLUCID

    4.1. I CNG V GLUCID

    Glucid l hp cht ph bin trong t nhin v trong c th sinh vt. Thnh phn m bo thc vt gm trn di 80%, cht kh l glucid, m bo ng vt c t hn, khong trn di 2%. y l loi cht hu c ph bin bc nht.

    Glucid thc vt c di dng cht x (cellulose dng tinh bt d tr, dng ng (sacarose, fructose...).

    ng vt, glucid c nhiu trong gan di dng glycogen d tr, hoc c trong huyt thanh di dng glucose.

    4.1.1. nh ngha v glucid

    Glucid l hp cht hu c mang nng lng, n l sn phm ca qu trnh quang hp: cy xanh nh dip lc bin CO2 v H2O thnh glucid di nh sng ca mt tri:

    C th ni glucid l nhng hp cht m quang nng chuyn sang dng

    ho nng d s dng i vi a s sinh vt.

    4.1.2. Vai tr ca glucid trong s sng

    Cung cp nng lng cho hot ng sng, hng ngy nhu cu nng lng ca ng vt c bo m 60 - 80% l do glucid.

    - Tham gia vo cu trc ca cc m bo (nht l m chng ). l vai tr to hnh ca glucid. V d: nhm cht quan trng ca c th l acid nucleic c thnh phn ng ribose v desoxyribose.

    - Ngoi ra, trong i sng hng ngy ca ngi v gia sc, nhng glucid nh tinh bt, ng, cellulose (rm, c, rau) chim mt t l quan trng trong thc phm.

    4.1.3. Cc tnh cht ca gluci

    4.1.3.1. Tnh cht l hc ca monosacand

    - Tnh ho tan v quay mt phng phn cc

    Cc monosacarid d tan trong nc, t tan trong ru, khng tan trong cc dung mi hu c (nh e, benzen) v c kh nng lm quay mt phng phn cc.

    - Tnh cht oxy ho kh

  • Cc monosacand th hin tnh kh mnh do s c mt cc nhm chc aldchyd v on t do. Trong mi trng kim v un nng, cc monosacand c th kh cc con tm loi (v d Cu2+ -> cui Tnh cht ny c s dng nh lng ng kh ni chung v glucose ni ring trong cc mu thc vt v ng vt. Khi kh cc monosacand ta thu c cc ru a nguyn t tng ng. Cc ru socbit, ribit vn c to thnh khi kh glucose (hoc fructose), ribose... thng gp trong c th sng v ng vai tr quan trng.

    - Phn ng to este

    Khi phn ng vi cc acid, cc monosacand to thnh cc este, trong c ngha quan trng nht l cc este phosphonc ca monosacand. Cc monosacand tham gia vo cc qu trnh trao i cht quan trng nht (nh quang hp, h hp) u dng este phosphoric: aldehyd-3-phosphoglyceric, phosphodioxyaceton, glucose-6-photphat, fructose-1,6-diphotphat, riboso-5-photphat...

    Phn ng vi hydrazin (NH2 - NH2) hoc phenylhydrazin (CH5 -NH- NH2) Monosacand tc dng vi phenythydrazin to thnh sn phm khng tan - phenylozazon mu vng. Phenylozazon c s dng nhn bit ng khi phn tch. S hnh thnh ozazon ca monosacand c th biu din nh sau:

    - Tc dng vi acid phosphonc

    4.1.4. Vn ng phn v mch vng ca monosacarid

  • 4.1.4.1. Vn ng phn

    Mt trong nhng c im ca glucid (v d nh glucose v nhiu monosacand khc) l tn ti di nhiu dng ng phn.

    Mi phn t monosacand, t loi c 3 carbon tr ln u cha t nht mt nguyn t carbon bt i (ngha l 4 ho tr carbon c bo ho bi 4 nhm ho hc khc nhau). V vy n c kh nng tn ti 3 dng ng phn.

    - ng phn quay phi tia phn cc (+)

    - ng phn quay tri tia phn cc (-)

    - Cht khng c hot tnh quang hc (raxemat)

    Hai ng phn u l 2 cht i khng v mt quang hc.

    Da.vo cc ng phn ca triose l glycerylaldehyd ngi ta chia cc mnose lm 2 hng tng ng: D v L.

    V tr nhn xt hng D v L cho cc ng l H v OH nguyn t carbon

    nm cnh nhm ru bc nht (CH2OH)

    - Nu OH nm bn phi l hng D

    - Nu OH nm bn tri l hng L

    Hng D v L ging nhau v nhiu c tnh l ha, chng ch khc nhau v kh nng lm quay mt phng tia phn cc. Ngoi ra, v mt dinh dng ca ng vt gi tr ca hai loi cng khc nhau. Trong c th ch yu c ng hng D.

    4.1.4.2. Vn mch vng ca monosacarid

    Trong cu trc ca monosacand ta thy c nhng gc hot ng cnh nhau nh aldchyd v alcol. Do chng c kh nng phn ng vi nhau to thnh dng dn xut na acetal (hemiacetal) theo s sau:

  • Khi phn ng xy ra trong phn t monosacand, mt cu ni oxy s c thnh lp v monosacand s ho dng vng.

    Dng vng ca monosacand c th l 6 cnh hay 5 cnh. Haworth ngh gi

    monosacand c dng vng 6 cnh l panose v monosacand c dng vng 5 cnh l furanose. V c th ci 2 dng ny nh l dn xut ca phn v furan.

    Cu ni oxy c th xut hin gia nguyn t C1 - C5 (dng Piranose) hoc C1- C4

    long furanose)

    V d:

    Haworth cng ra cng thc phi cnh biu din monosacand.

    dng vng glucose (hoc cc monosacand khc) c kh nng tn ti di dng ng phn khng gian a v Hai loi ny khc nhau do v tr H v OH nguyn t Cl.

  • i vi monosacand lp cetose nh fructose cng c th dng na acetal,

    nhng u ni oxy s xut hin gia C2 - C5 hoc C2 - C6

    4.1.5. Cc monosacarid ph bin

    Trong t nhin v trong c th ng vt thng gp cc monosacand sau:

    4.1.5.1. D - Glucose (cn gi l ng nho)

    y l loi ng ph bin nht c nhiu trong hoa qu. Trong mu ca gia sc cha trung bnh 80 - 120mg%, glucose gan, bp tht c trng hp v d tr dng glycogen.

    Glucose c c tnh ca ng n (kh nng oxy - ho kh, dng vng, quay tia phn cc...).

  • 4.1.5.2. D - Galactose: cn gi l ng sa, c trong thnh phn ng 1actose

    sa v dng hp cht galactosid ca no (xerebrosid)

    4.1.5.3. D - Fructose (fructus - qu) C nhiu trong qu chn, c v ngt mnh

    nht.

    4.1.5.4. D - Manose: c coi l epimer ca D - glucose v ch khc glucose v

    tr C2 v nhm o.

    Manose thng thy hoa qu (v cam) v trong phc hp vi my loi protein (nh albumin, globulin, cht nhy mucoid)

    4.1.5.5. Cc pentose: l loi monosacand 5 carbon, trong t nhin c di dng a ng pentosan ( rm, c) hoc mt t t do ( qu chn).

    Trong c th gia sc c D - ribose v D - desoxyribose l nhm cht quan trng

  • nht trong nucleoproteid.

    4.1.6. Cc dn xut chnh ca monosacarid

    4.1.6.1 . Cc phospho - este (hesose - phosphat)

    Cc monosacand nh glucose, fructose... trong m bo sinh vt d este ho vi H3ro4 thanh dng glucose - phosphat.

    Loi cht ny rt quan trng trong qu trnh trao i vt cht v gii phng nng

    lng cho c th ng vt.

    4.1.6.2. Dn xut cha quan (hexosamin)

    Mt nhm OH (thng v tr C2) c thay bng NH2

    Trong c th ng vt, loi ng quan ny c trong protein cht nhy cu trc mt s m.

    Hai cht thng gp:

    4.1.6.3. Nhm glucosid

    V cu to, glucosid l nhng hp cht este gia monosacand v cht khng glucid nh ru, metyl, acid xyanhydric gi chung l gc aglucon.

    Phn ln glucosid t nhin l nhng cht c, nhng vi liu lng nh va phi li c dc tnh rt gi tr. V d: Saponin (ng + saponegin) l thuc long m.

    4.2. PHN LOI GLUCID

    C s phn loi: Ngi ta thng phn loi glucid da theo mc phc tp ca phn t, ly ng n lm c s.

  • Chia lm 2 loi chnh:

    4.2.1. Loi ose

    O se l nhng ng khng thu phn c na thng cn gi l ng n hoc monosacand. Tu theo s nguyn t carbon, loi OZA chia thnh cc nhm:

    - Triose (C3H6O3)

    - Tetrose (C4H8O4)

    - Pentose (C5H10O5)

    - Hexose (C6H12O6)

    4.2.2. Loi osid

    L nhng glucid phc tp do nhiu monosacand ghp li. Loi ny gm 2 nhm ln:

    4.2.2.1. Holosid

    Khi thu phn cho ton monosacand, nn cn gi l glucid n thun, nhm ny chia ra thnh:

    Oligosacand (hoc oligose): cu trc n gin gm t 2 n 3 monosacand nn cn gi l disacarid v trisacand.

    - Polysacand (polyose) cu trc rt phc tp gm nhiu monosacand, mt s i din nh: tinh bt, glycogen, cellulose...

    4.2.2.2. Heterosid

    Khi thu phn, ngoi monosacand cn thy nhiu nhm khng phi glucid (nhm aglucon).

    Di y ta ln lt nghin cu tng loi ni trn.

    4.3. LOI OSE

    Xt v cu trc, monosacarid l nhng dn xut aldehyd v ceton ca ru nhiu nguyn t v tng t nh vy ta c alose hoc cetose.

    4.3.1. Triose (C3H6O3)

    y l nhng monosacand c 3 nguyn t cathon. i din ca nhm ny l

  • glycerylaldehyd v dioxyaceton.

    4.3.2. Tetrose (C4H8O4)

    Tetrose l monosacand m phn t ca n c 4 carbon. Trc kia loi ny khng c cc nh sinh vt hc ch lm, nhng sau ny ngi ta thy khi thu phn glucid, trong nhng sn phm trung gian ca qu trnh trao i cht, cng vi dng phosphoryl ca loi hexose, pentose, cn c dng tetrose nh eritrophosphat.

    4.3.3. Pentose (C5H10O5)

    Mt s i din ca loi monosacand 5 carbon ny l:

    4.3.4. Hexose (C6H12O6)

  • Trong c th ng vt v ngi, nhng hexose thng gp l: glucose, fructose, mannose, galactose (mt phn hexose trng thi t o, mt phn dng lin kt trong thnh phn ca polysacand. Hexose t nhin: glucose, fructose, mannose, galactose thuc loi cu trc dy D - trong iu kin phng th nghim c th nhn c ng dy L.

    Tt c monosacand t nhin c v ngt v d ho tan trong nc. ngt ca mi loi ng khng ging nhau.

    Monosacand loi hexose tng i ph bin nh chng ta trnh by trn.

    4.4. LOI OSID

    Osid gm 2 loi chnh:

    - Loi osid thun nht (hay cn gi l holosid) gm ton o se.

    - Loi osid khng thun nht (heterosid) loi ny ngoi cc o se ra cn c nhm ghp khng phi glucid.

    Ta ln lt nghin cu my loi ph bin sau y:

    4.4.1. Loi holosid

    Tu s lng monosacand to thnh m nhm holosid chia ra: disacand, tnsacand, polysacand.

    4.4.1.1. Disacarid. (hay cn gi l ng kp)

    N c thnh lp do 2 monosacand hp li qua mch osid sau khi kh i mt phn t nc .

    Thnh phn nhng ng kp ch yu nh sau:

    My cht ng ch l:

    - Saccarose: ( glucosido - 1,2, - fructose) lin kt glucosid gia C1 ca glucose v C2 ca fructose.

  • Loi ny cn c gi l ng ma hay ng c ci ng (ma c 20%, c ci

    ng c 27%).

    Saccarose khng cn nhm OH glucosid t do nn khng cho nhng phn ng oxy - ho kh.

    - Lactose ( - galactosido - 1,4, - glucose) ng ca sa hm lng lactose thay i tu loi sa. y l loi ng kp c nht c tng hp c th gia sc - Lactose c tnh oxy ho kh in hnh ca ng.

    Maltose ( - glucosido 1 ,4 - - glucose)

    Cn gi l ng mch nha. ng ny sinh ra trong ng tiu ho do s thu phn tinh bt hoc glycogen bi men amylase.

    - Cellohiose: ( - glucosido - 1,4, - glucose) l ng kp thu c khi thu

    phn cellulose cha trit .

  • 4.4.1.2. Polysacarid

    Polysacand l loi a ng c trng lng phn t rt cao, do nhiu gc monosacarid hp li m thnh. Cng thc chung ca polysacand l (C6H10O5)n.

    cc loi polysacari ng k nht l:

    - Tinh bt

    - Glycogen

    - Cellulose

    - Chitin

    Tinh bt

    Tinh bt l loi glucid d tr ca thc vt c lluul thnh trong qu trnh quang hp. N l ngun thc n rt quan trng i vi ng vt, nht l ng vt nng nghip. Phn ng c trng nht ca tinh bt l tc dng vi iod (hoc dung dch lum) cho mu xanh chm.

    Hm lng ca tinh bt khc nhau cc loi thc vt:

    V d: go t cha khong: 75,81%

    ng cha khong: 70,08%

    Cu to ho hc ca tinh bt c to thnh t cc gc a glucose gm 2 thnh phn: + Amylose (chim 10 - 20%) - cht ny tan trong nc, khng to h, vi iod cho mu xanh, cc gc a - glucose c lin kt vi nhau qua mch glucosid 1 - 4 to thnh mch thng.

    + Amilopectin (chim 80 - 90%) khng tan trong nc vi iod cho mu tn

    gm cc gc a - glucose lin kt vi nhau qua mch glucosid 1- 4 v 1-6 to cho phn t tinh bt c cu to phn nhnh.

  • Glycogen (hay cn gi l tinh bt ng vt)

    l loi glucid d tr trong gan v m bo ng vt. Cu to ho hc ca glycogen ging tinh bt, tc l cu to t cc - glucose, nhng mc phn nhnh ca glycogen mnh hn .

    Ceuulose (hay cn gi l cht x)

    l loi polysacarid ph bin nht ca thc vt. N c cu to t nhiu gc - glucose qua mch - glucosid 1- 4 to thnh chui thng khng phn nhnh, s lng - glucose khong vi chc vn. Trong thc vt, cellulose lin kt thnh cc b si l cc mi xen qua cc lin kt hyrogen.

    Ceuulose ch b phn ho bi enzym ceuulase vi sinh vt cho nn c th gia sc

    mun s dng cellulose phi nh s hot ng ca vi sinh vt c trong d c ca loi nhai li bi v trong c th gia sc khng c enzym cellulase.

    Ngoi cc loi ng thng gp ni trn chng ta cn gp mt s a ng nh: chinh, mun, hemicellulose, dextran...

    Chitin

    Chitin l mt polysacand thun c cu to t cc n v N-acetylglucosanlin ni vi nhau bng lin kt - glucosid 1- 4. S khc nhau duy nht v mt ha hc gia chnh v cellulose l s thay th nhm hydroxyl v tr C2 bng mt nhm c acetyl ha (CO3-CO-NH-):

  • Chitin c dng si ging nh cellulose v ng vt cng khng tiu ha c

    chnh. Chitin l thnh phn c bn ca lp v cng ca nhiu loi sinh vt, l polysacand ph bin trong t nhin ch sau cellulose.

    Inulin: l mt polysacand d tr ca thc vt. n v cu to l fructose. Trng lng phn t ca insulin thp v n ch c khong 30 gc fructose, do polysacand ny d dng ho tan trong nc.

    loi ng cc thi k pht trin u thng c a ng cu to do fructose. Khi chn mui a ng ny s pht trin thnh tinh bt.

    Hemiceuulose: y l tn chung ca nhiu loi a ng thng gp trong rm, g, li ng...

    a ng loi ny nu c n v cu to t:

    + Mannose th gi l mannan

    + Arabinose th gi l araban

    + Galactose th gi l galactan

    + Cylose th gi l cylan

    Dextran: l sn phm ca vi khun

    Dextran cu to t -glucose ni mch glucosid 1 - 4 v 1 - 6, nhng khc glycogen, mch glucosid 1 - 4 y l mch r.

    4.4.2. Loi heterosid

    Heterosid l loi a ng khng thun nht, c cu to cao phn t v cu trc phc tp. Trong thnh phn ca n ngoi cc monosacand ra cn c cc dn xut ca monosacand nh hexosamin, hexosulfat...

    Heterosid chia lm nhiu lp khc nhau tu tnh cht v cu trc. ng k nht l 2 lp:

    - Glucopolysacand

    - Mucopolysacarid

    4.4.2.1. Mucopolysacarid: (mucor - cht nhy)

    y l loi a ng thng gp trong m lin kt, cht trung gian gia cc t bo v cc dch nhy. Ba loi mucopolysacand ng ch l:

  • - Acid hyaluronic

    Loi a ng nhy ny c trong dch bao khp, trong thu tinh th mt, trong nhiu m bo ca ng vt khc.

    Trng lng phn t khong 200 - 500 nghn, ho tan trong dung dch rt nht. Nh c tnh ny nn acid hyaluronic c v nh cht xi mng gn vi cc t bo ca m trong c th.

    Khi thu phn acid hyaluronic ta thu c N- acetylglucosamin v acid D-glucoronic.

    Hai thnh phn ny ni vi nhau theo s d on sau:

    Nhiu vi khun c kh nng ph hoi mch m bo, nc ong, nc rn... c loi

    enzym hyaluronidase phn gii acid hyaluronic. Enzym ny lm hng cht nhy gn t bo nn vi khun d hot ng.

    u mi nhn ca tinh trng cng c acid hyaluronic nn tinh trng c kh nng xm nhp vo t bo trng thc hin qu trnh th tinh.

    - Chondroitin sulfat

    Cht ny cha nhiu trong m lin kt, cht tnh kim ca sn di dng phc cht nhy chondromucoid.

    Trng lng phn t rt cao gm acetyl-galactosamin, acid glucoronic - cu trc d on nh sau:

    Heparin (Hepar - gan)

    y l loi a ng tm thy u tin gan, sau c, tim, phi...

    Trng lng phn t khong 17.000 thnh phn gm galactosamin, acid glucoronic v gc sulfat.

  • Hepann c kh nng lin kt vi trombokinase, lm cho cht ny khng tham gia

    vo qu trnh ng mu c. Chnh ming con a cng c cht hepann ny, cho nn khi a cn mu thng chy ra nhiu, kh ng.

    Trong y hc v th y hepann c dng lm cht n nh mu v chng ng mu (khi truyn mu).

    4.4.2.2. Glucopolysacand

    L loi a ng phc tp c tnh keo nh mucopolysacand nhng khng cha dn xut an lin nh hexosann. i din ca nhm ny thng l:

    - Pectin thc vt: l nhng cht gi vai tr nha gn t bo m thc vt.

    - Glucopolysacand ca vi khun: thng c trong cu to gip m, c c tnh bn i vi men tiu ho. 'Nh vy vi khun sng c trong nhng mi trng nh nc bt, dch rut...

  • Chng 5

    LIPID

    5.1. I CNG V LIPID

    5.1.1. Khi nim chung

    Lipid l lp hp cht hu c ph bin trong t nhin v trong c th ng vt, thc vt v vi sinh vt. Lipid c c tnh khng ho tan trong nc, ch ho tan trong cc dung mi hu c nh e, cloroform, benzen, cn, aceton... (nhng khng phi mi lipid u ho tan nh nhau trong tt c cc dung mi ni trn, m mi lipid ho tan trong dung mi tng ng ca mnh, nh c tnh ny ngi ta c th phn tch ring tng loi).

    Tn gi lipid (bt ngun t ch Hy-lp lipos: m) dng ch chung cc loi m, du v cc cht bo ging m ng vt v thc vt.

    V mt ho hc lipid l nhng este gia alcol v acid bo in hnh l cht triglycerid.

    5.1.2. Vai tr ca lipid

    Lipid i vi c th sinh vt c nhiu ngha quan trng:

    Chc nng d tr nng lng

    Lipid l cht d tr nng lng, tit kim th tch nht, khi oxy ho 1 gam m c th thu c 9,3 Kem. em so vi lng cm ca mt gam ng hoc protein (4,l Kcalll gam) th lng cam sn ra ca lipid nhiu gp i. Nhu cu nng lng hng ngy ca ng vt do m cung cp khong 30% hoc hn na.

    Chc nng cu to mng t bo

    Trong mng sinh hc lipid trng thi lin kt vi protein to thnh hp cht lipoproteid chnh nh tnh cht ca hp cht ny to cho mng sinh vt c c tnh thm thu chn lc, tnh cch in. l nhng thuc tnh ht sc quan trng ca t bo sinh vt.

    Chc nng dung mi ho tan vitamin

    Lipid l dung mi ho tan nhiu loi vitamin quan trng nh vitamin A, D, K, E. V th nu khu phn thiu lipid lu ngy th ng vt d mc bnh thiu vitamin k trn.

  • Chc nng bo v c hc

    Lipid di da ca ng vt c tc dng gi m v gi m cho c th nh tnh m, dn nhit km.

    Chc nng cung cp nc ni sinh

    i vi loi ng vt ng ng, ng vt di c, cc loi su kn lipid cn l ngun cung cp nc, v khi oxy ho long m th c l07g nc c sinh ra.

    Ngoi ra, lipid cn c th lin kt vi nhiu cht n gin khc thnh nhng phc hp c tnh cht sinh hc khc nhau. Nhng phc hp y gi vai tr quan trng trong cc hot ng v thn kinh v bp tht.

    5.1.3. Thnh phn c bn ca lipid

    Trong phn ln cc cht lipid c cha hai thnh phn chnh l alcol v acid bo.

    Alcol v acid bo c ni vi nhau bng lin kt este hoc lin kt amid. Ngoi ra, lipid cn c th kt hp vi glucid to thnh glucolipid c vai tr cu trc mng hoc kt hp vi protein to thnh lipoprotein gi vai tr quan trng trong vic ho tan v vn chuyn lipid trong mu, gip hp thu vitamin tan trong lipid.

    5.1.3.1. Alcol ca lipid

    Alcol ca lipid c chia thnh nhiu nhm khc nhau: glycerol, cc alcol bc cao, aminoalcol v sterol. Ngoi ra, trong t nhin cn c alcol khng no, v d phytol (l mt thnh phn ca chlorophyl v lycophyl) l mt dthydroxylalcol khng no c nhiu lin kt i l cht mu ta trong c chua.

    Glycerol l mt alcol a chc c trong thnh phn cu to glycerid v phosphatid.

    Cu trc ca glycerol nh sau:

    cc alcol cao phn t thng tham gia vo thnh phn ca cc cht sp.

    Aminoalcol tham gia vo thnh phn cu to ca cerebrosid v mt s phosphatid, Aminoalcol thng gp l:

    - Sphingozin (thnh phn cu to ca sphingolipid):

    - Cerebrin c nhiu trong nm men, ht ng):

  • - Sterol: tiu biu cho sterol l cholesterol trong m bo ng vt. Sterol khi este ha vi acid bo to thnh sterid.

    5.1.3.2. Acid bo

    Tnh cht ca lipid ph thuc rt nhiu vo thnh phn acid bo. Acid bo c nhiu oi: mch thng, mch nhnh, mch vng. bo ho (no) ca acid bo khc nhau gy ho m c tnh tan chy cc nhit ring bit. Tr mt vi trng hp c bit, cn hn ln cc acid bo u cha chui cc bon chn.

    Cc acid bo thng gp:

    Tn gi cng thc Ni c nhiu

    - Acid butylic

    - Acid caproic

    - Acid caprylic

    - Acid palmitic

    - Acid steanc

    - Acid arachidic

    CH3(CH2)2 COOH CH3(CH2)4 COOH

    CH3(CH2)6 COOH

    CH3(CH2)14 COOH

    CH3(CH2)l6 COOH

    CH3(CH2)18 COOH

    M sa (b)

    B, da

    B, da, no c

    Du m ng, thc vt

    Du m ng, thc vt

    Du lc

    5.2. PHN LOI LIPID

    C s phn loi lipid: Da vo thnh phn ho hc ngi ta chia lipid ra lm 2 lp: Lp lipid n gin: l nhng este ca alcol v acid bo.

    - Lp lipid phc tp: ngoi alcol v acid bo cn c cha cc dn xut phospho, azot, sulfua...

    5.2.1. Lp lipid n gin

    Bao gm: - Cc glycerid trung tnh

    - Cc sp tc cerid

    - Cc sterid

    5.2.1.1. M trung tnh (triglycerid)

    * i cng

    Cht bo l este ca glycerin v acid bo, do ngi ta cn gi l glycerid.

    M d tr trong c th cc m m. S lng ca n thay i tu trng thi h thn kinh, tu khu phn, tu ging c ci, tu tui v cc yu t khc na. S lng c th x dch trong khong 10 - 30% so vi th trng (ln v bo c th ln ti

  • 50%).

    * Cng thc cu to ho hc ca m (triglycerid)

    Nu R1, R2, R3 ging nhau gi l m ng nht, cn Rl, R2, R3 khc nhau gi l

    m hn hp. Loi sau thng ph bin hn.

    V d:

    * L ha tnh ca lipid

    Nhit tan chy ca m thp

    Mi loi m c tan chy khc nhau ph thuc vo bo ho ca acid bo m n cha. bo ho thp th nhit tan chy thp v ngc li. Nhit tan chy ca mt s loi m nh sau:

    M b: 25 - 300C

    M ln: 36 - 450C

    M g: 33 - 400C

    Du lc: - 340C (m)

    Trong mt c th ng vt, m cc m khc nhau nn nhit tan chy cng khng ging nhau.

    - Tnh nh tng (emulsio)

    M khng ho tan trong nc v do t trng thp (0,866 - 0,973) n ni trn mt nc. Khi cho vo hn hp nc v m mt s cht nh protein, acid mt, x phng v lc mnh th sau ta c mt dung dch gi, mu sa gi l nh tng. Trong nh tng, m b phn tn thnh nhng ht nh ly ty v mi mt ht b c lp bi mt lp cht gy bn nh tng (x phng, acid mt...) v lp nc. Nguyn nhn ca hin

  • tng l do cc cht ny lm gim sc cng b mt ca ht m nn m b phn tn

    nh v khng lin kt thnh khi vi nhau c, trong qu trnh tiu h