giao trinh hoa sinh_up

8/3/2019 Giao Trinh Hoa Sinh_up

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QU HAI (CH BIN) - NGUYN B LCTRN THANH PHONG - CAO NG NGUYN

GGIIOO TTRRNNHH

HHAA SSIINNHH

NH XUT BN I HC HU

Tai lieu chia se tai: wWw.SinhHoc.edu.vn



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Mu

1. Lch s, i tng, nhim v ca ho sinh th k XIX, khi m ho hc pht trin nh v bo, th ranh

gii gia sinh hc v ho hc xut hin mt lnh vc khoa hc minhm nghin cu thnh phn ho hc ca cth sng v nhng qu trnhchuyn ho ho hc ca cc cht v ca nng lng trong qu trnh hotng sng xy ra trong cth ca chng. Lnh vc khoa hc ny c gil ho hc sinh vt hoc vn tt hn- ho sinh hc (biochemistry).

C th ni rng, ho sinh hc l mt phn lnh vc ca khoa hccuc sng. Nhim v ca chng nhm nghin cu cc hin tng sng

bng cc phng php ho hc.y l mt khoa hc tr tui ca th k XX ang trn pht trin

mnh m v ang xm nhp vo nhiu lnh vc mi nhn ca sinh vt hc,y hc v nng hc... Ho sinh hc mi trthnh mt khoa hc c lp vona sau th k th XIX mc du ngay t thi thng c con ngi lmquen vi nhiu qu trnh ho sinh hc trong cuc sng hng ngy ca h(nu ru, nng bnh m, thuc da, lm dm, tng, nc mm...).

Tuy vy ch mi gn y, tt c mi qu trnh sinh hc ny mic nghin cu mt cch khoa hc v c gii thch mt cch y .

C th ni, s xut hin mn ho sinh hc l kt qu tt yu ca spht trin v phi hp gia ho hc v sinh vt hc.Tnh cht v phng hng ca ho sinh hc l nghin cu trn c

th sng, tm ngha chc phn ca tt c mi thnh phn, mi sn phmchuyn ho, trn cs, tm hiu su v:

- Mi lin quan gia qu trnh ho hc v sinh vt hc.- Mi lin quan gia cu trc v chc nng sng ca cc cquan

trong cth.- Cchiu ho ton b qu trnh sng.Tu theo i tng nghin cu m ngi ta phn chia ho sinh hc

thnh ho sinh ng vt, ho sinh thc vt, ho sinh vi sinh vt v y hosinh.

Trn mi i tng, ho sinh nghin cu song song hai mt "tnh"v "ng".

Vic nghin cu cc cht c trong thnh phn ca c th sinh vtl nhim v ca tnh ho sinh. Tnh ho sinh gn lin rt mt thit vi hohc sinh hu c. y chnh l ha sinh m t.

Cn vic nghin cu cc chuyn ha ho hc xy ra trong qutrnh hot ng sng ca cth ngha l nghin cu v mt ho hc ca s




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trao i cht trong mi lin quan vi ton b c th v mi trng xungquanh l nhim v ca ng ho sinh.

Tnh ho sinh v ng ho sinh lin quan vi nhau rt cht ch -vic nghin cu cc qu trnh ha sinh hc s v ngha nu khng c snghin cu cc cht tham gia trong cc qu trnh ny.

Ho sinh m t gn lin vi s pht trin ca ho hu c. Cui thk XVIII, u th k XIX, hng lot cc hp cht hu c c tch rat thc vt v t cc t chc ng vt: citric acid, malic acid, tatric acid,oxalic acid, urea v cc alkaloid. Ngi ta xc nhn rng trong thnhphn ca tt c cc cht bo u cha glycerin. Trong thi gian ny,Lavoisier cng gii thch c c ch ho hc ca s h h p v schy. ng chng minh rng, lng nhit do cc cth sng sn sinh ra

cng bng lng nhit thu c khi t chy cc cht dinh dng bnngoi c th (khi h hp trong c th, carbon v hydrogen b oxy ha tt, qu trnh ny rt ging s chy bnh thng).

Tip theo cc cng trnh chit xut, tinh ch v phn tch cc chthu c l nhng cng trnh nghin cu tng hp cc cht hu c. Quanim cho rng, vt cht sng khc vi vt cht khng sng bnh hon ton khi m Whler vo nm 1828 iu chc carbamid (urea)bng phng php nhn to t cc cht v c. Pht minh ca Whler lbng chng cho rng to nn cht sng khng cn thit bt k mt

"lc" sng no (vis vitalis) v nh vy mng hng cho hosinh pht trin. (Thi k ny khoa hc i su vo s sng ang b khngch v km hm bi thuyt "hot lc" cho rng cc cht hu c tham giavo cu to ca c th sinh vt ch c th to ra bi mt "ng siu tnhin").

Trong sut khong hai th k trc, s pht trin ca ho sinh hcxy ra tng i chm. S bt u tht s ca ho sinh hc thng ccoi l vo nm 1866 khi Tbigen thnh lp b mn ho sinh u tin dis lnh o ca Hoppe - Seyler ( nc c). Su tin ca t p chmang tnh cht ho sinh hc c ra mt vo nm 1877 (Hoppe - Seyler'sZeitschrift fr physiologische Chemie). Tin ca n l s hot ng caLiebig c v trng phi ho hc hu cca ng. Bng cch s dngcc phng php nghin cu mi, Liebig xc nh thnh phn canhiu thc phm, chia cc cht cha trong thc phm thnh protein,glucid, lipid v xc nh hm lng nitrogen trong protein. Sau nhngcng trnh nghin cu ca Pasteur v s ln men, cc nh khoa hc ch nhiu n bn cht enzyme vn xc tc cho cc qu trnh khc nhautrong cth sng. Nhiu cng trnh c gi tr khc, trong c cng trnhca Fischer i vo cu trc v tng h p glucid, lipid, amino acid v




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protein, Pavlov trong thi gian ny nghin cu cc cch enzyme vMiescher th nghin cu nucleic acid. Thi gian ny ngi ta cng phthin ra vitamin.

Vic xc lp nn thnh phn ho hc ca thc vt, vic pht hinra cc enzyme v vic lm sng t vai tr ca chng trong s trao i cht,s pht hin ra vitamin v hormon, s pht trin ca ho hc v aminoacid v protein, v glucid, lipid to iu kin cho vic hnh thnh ngho sinh v chnh nhs pht trin ca ng ho sinh m ngi ta xydng c nhng quan im thng nht v cc quy lut chung ca cc qutrnh trao i cht v ca nhng chuyn ho nng lng trong cth sinh vt.

Ngy nay chng ta bit r rng, tt c cc cht xy dng nn t bosng, u thay i khng ngng.c trng ca s sng l s bin i ho hc.

Nh vy ho sinh hc hin i trc ht l ng ho sinh. Trctin l nhng hin tng trao i cht, l s chuyn ho v phn giicc cht dinh dng nhm thu nhn nng lng ho hc cng nh xydng vt cht ca t bo. Cc phn ng ho hc ny c xy ra nhtcdng xc tc ca nhng enzyme, v vy vic nghin cu cc enzymechim mt phn quan trng trong ho sinh hc.

Thn thuc vng ho sinh l iu ho ho hc. iu nyc xy ra trn con ng cc sn phm trao i cht xc nh, thng lcng vi s tham gia ca nhng cht c bit l hormon c to thnh

trong cc tuyn ni tit.Th ba thuc vng ho sinh l cc qu trnh ho hc c xyra gn lin vi cc cu trc v thc hin cc chc nng ca cc phn tcu trc.

Vic xc nh trnh t ca amino acid trong protein v cu trckhng gian ca protein (Sanger, Perutz v Kendrew) cng nh cu trcca nucleic acid (Chargaff, Watson v Crick) l bt u mt giai on mitrong s pht trin ca ho sinh hc tc l thi k ca sinh hc phn t.Mt iu r rng l khng th tch ring sinh hc phn t v ho sinh hcra khi nhau. V c bn m ni th "sinh hc phn t" ch l tn mi,nhng l mt phn ngnh ring ca ho sinh. N c gng lm sng t cchin tng sng cbn trn csphn t c ngha l trn csho sinhhc. Chnh v vy theo quan nim hin i th ho sinh hc l khoa hcnghin cu csphn t ca s sng.

2. Thnh phn ho hc ca cth sngTrong cth sng, nc l thnh phn quan trng nht. Tr mt s

m hoc loi t bo (cc ht thc vt, cc bo t m xng, m m),lng nc ca chng khng t n 80%, cn lng nc ca mt ssinh vt khc cng vt qu 90% (ton b lng nc ca c th con




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ngi khong 50-70%). iu cn lu l mt s dng sng bc thp, ccvirus, cc bo t sng qua trng thi kh ho hon ton, song trong trngthi khng c nc th cc hot ng sng ca chng b hon li.

T cc c s trn chng ta c th ni rng cc qu trnh ho hcc trng cho s sng c xem nh l nhng phn ng tin hnh trongmi trng nc.

Ngoi ra ngi ta pht hin c hn 60 nguyn t c trong cth sng. Cc nguyn t ny c trong c th vi nhng lng rt khcnhau. Mt sc coi l nhng nguyn t cn thit xy dng cth vphc v cho s pht trin bnh thng ca c th; mt s khc th chcnng sinh hc ca chng cha c bit r; s cn li c coi nh do sxm nhp ngu nhin. C H O N S P Cl Ca Mg K Na u l nhng nguyn

t rt cn thit i vi c th sng, 11 nguyn t ny chim gn 100%khi lng ton phn ca thc vt v ng vt. Nhng nguyn tdngvt c gi l yu t vi lng, vai tr quan trng ca chng i vi cucsng cng dn dn c sng t l nhng ion kim loi nng Co, Zn,Mn, Mo; trong trng hp cc cthng vt bc cao cn c I, cc cyxanh th c B. Cn nh rng, tr I v Mo, cc nguyn t c knu nm trong s 30 nguyn tu ca h thng tun hon v hn mtna cc nguyn t c s th tn 30 c vai tr sinh hc quan trng.

Nhiu hp cht hu ctrc y c coi nh l ring bit thuc

gii sinh vt, nay cng c nghin cu, tng h p trong phng thnghim. l cc protein, nucleic acid, glucid, lipid, enzyme v vitamin.y l nhng cht chim v tr hng u trong sinh hc v cng chnh li tng nghin cu chnh ca cc chng trong gio trnh ny.

3. Mi quan h ca ho sinh vi cc ngnh khoa hc ca sinhhc, nng nghip v y hc

Trong sinh hc c nhiu ngnh, nhng nghin cu sinh hc ngynay l nghin cu mc phn t. Ho sinh l khoa hc nghin cu ssng mc phn t, cho nn c th ni bt c chuyn ngnh no casinh hc nhng vt hc, thc vt hc, vi khun hc, sinh l hc, t bohc, m phi hc... u cn phi trang b kin thc v k thut ho sinh nghin cu khoa hc chuyn ngnh mnh. Do khi ni n cc chuynngnh ca sinh hc hin i th trc ht phi ni n ho sinh trongnhng nm gn y. Ngay c cng ngh gen, cng ngh enzyme cngchnh l lnh a ca ho sinh. Chng hn i vi ng vt, thc vt, visinh vt, ngy nay mun nghin cu phn loi chnh xc cc ging chngcng phi dng cc ch tiu phn t mt s protein, enzyme hay nucleicacid trong ty lp th. i vi nng nghip mun tng nng sut cy trngphi ch n qu trnh ho sinh quang hp, qu trnh ho sinh ny mm,




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qu trnh ho sinh pht dc, qu trnh chuyn ho, sinh tng hp cc chtto nn ht, qu, qu trnh tc ng ho sinh ca cc cytokinin n s sinhtrng v pht trin ca cy. i vi vt nui cng vy, mun c nngsut tht, sa, trng cao, ngi chn nui phi hiu c cc qu trnh hosinh pht trin n tng giai on pht trin ca con vt, n tng b phnc b p, bung trng ca chng c s tc ng mnh m. i vi ydc hc, vn ch cht nghin cu bnh nguyn, bnh l, chn on viu tr bnh cng u lin quan cht chn ho sinh, tc lin quan ns thay i cc phn t bnh l xy ra trong cth v tm nhng cht hottnh sinh hc c tc dng phng chng hoc cha khi bnh.

V vy c th ni ho sinh l gc, l cbn gip hiu su sccc khoa hc khc ca sinh hc, nng nghip v y hc.

4. Mt s thnh tu ni bt ca ha sinh trong thi gian gn yTrong qu trnh pht trin ca mnh, nhiu ngnh nh ca ho sinh

ra i.V ho sinh mt s chc phn h thng quan trng c ho sinhmin dch, ho sinh di truyn, c bit mt ngnh mi gn y xuthin l cng ngh ho sinh. Cc lnh vc nh ca ho sinh ng gpmt cch tch cc vo thnh tch chung ca ho sinh. Nhiu gii thngNobel ghi cng cc kt qu nghin cu quan trng, m ra nhiu cnhca mi cho s pht trin ca ho sinh nh ho sinh ca h thng mindch ca Snell, Bena Cerraf v Dausset nm 1980. Cng nm y Paul Berg

cng c gii thng Nobel bi cng trnh nghin cu gn cc muDNA. Nm 1981-1982, thnh tu tng hp gen - interferon gm 514 ibase bi Leicester c thc hin. T n nay hng lot cng trnhkhc v nghin cu ho sinh c p dng trong lnh vc khoa hc.

Gn y, nm 1997 gii thng Nobel y hc trao cho StaleyPrusiner v cng trnh nghin cu prion, mt khi nim mi v "nhimkhun", gy bnh no th xp ngi v ng vt. Prion (PrP) l proteintn ti hai dng ng phn alpha v bta. c th kho mnh th PrP cdng alpha cn khi c th b bnh th dng alpha b dui ra v xp thnhcc bng song song gi l PrP bta. Dng ny rt bn vi enzyme tiu hov khng b ph hunhit cao (n 200oC). Do vy prion nh l tcnhn gy bnh hon ton mi c b sung vo danh sch nhng tc nhngy bnh nh virus, vi khun, nm. Cng trnh ny a ra khi nim bnhl phn t hon ton mi trong sinh hc v y hc. Cng trnh khng chpht hin ra tc nhn gy bnh xp no m cn t nn mng cho s tmhiu cch mt tr lin quan n bnh gi v bnh Alzheimer, cng nht nguyn tc cht ch cho vic ghp cc cquan ph tng ca ng vtcho con ngi v thuc men ch tng vt dng cho ngi.




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TI LIU THAM KHO

Ti liu ting Vit1. Trn Th n (ch bin). 1979. Ha sinh i cng (tp I, II). NxB KH&KT.H Ni.

2.i Duy Ban. 2005. Ha sinh hc v ha sinh y hc. Ha sinh hc. 1: 8-13.

3. Phm Th Trn Chu, Trn Th ng. 2000. Ha sinh hc. Nxb Gio dc. HNi.

4. L Don Din. 1975. Ha sinh thc vt. Nxb Nng nghip. H Ni

5. Nguyn Tin Thng, Nguyn nh Huyn. 1998. Gio trnh sinh ha hin

i. Nxb Gio dc. H Ni.6. Nguyn Xun Thng, o Kim Chi, Phm Quang Tng, Nguyn Vnng, 2004. Ha sinh hc. Nxb Y hc, H Ni.

Ti liu ting nc ngoi1. Karlson. P., 1972. Biokmia. Medicina Knyv Kiad Budapest.

2. Lehninger A.L., 2004. Principle of Biochemistry, 4th Edition. W.H Freeman.

3. Stryer L., 1981. Biochemistry. W.H.Freeman and company. San Francisco.

4. Straub .F. B. 1965. Biokmia. Medicina Knyv Kiad Budapest.




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Chng 1

Saccharide

L h p cht hu cc to nn t cc nguyn t: C, H, O ccng thc cu to chung Cm(H2O)n, thng m = n. Do c cng thc cuto nh trn nn saccharide thng c gi l carbohydrate - c ngha lcarbon ngm nc.

Tuy nhin c nhng saccharide c cng thc cu to khng ngvi cng thc chung ni trn v d: deoxyribose (C5H10O4).

C nhng cht khng phi l saccharide nhng c cng thc cu

to ph hp vi cng thc chung trn v d : acetic acid (CH3COOH).Saccharide l thnh phn quan trng trong mi sinh vt .

thc vt, saccharide chim t 80 - 90% trng lng kh,saccharide tham gia vo thnh phn cc m nng , v d cellulose, haytch tr di dng thc phm d tr vi lng ln, v d tinh bt. ng vt,hm lng saccharide thp hn nhiu, thng khng qu 2%, v d glycogen.

1.1. Monosaccharide

1.1.1. Cu to v danh phpL cht c cha nhiu nhm ru v mt nhm kh oxy (nhm kh l

nhm carbonyl l aldehyde hay ketone).

- Nhm kh l aldehyde ta c ng aldose v c cng thc tng qut:

CHO

(CHOH)n

CH2OH- Nhm kh l ketone ta c ng ketose c cng thc tng qut:

CH2OH

C= O

(CHOH)n

CH2OH




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CHO - CH2OH c xem nh l monosacchariden gin nht.

Trong thin nhin monosaccharide c cha t 2 n 7 carbon v c

gi tn theo s carbon (theo ting Hy Lp) + oseV d: monosaccharide c 3C gi l triose. Tng t ta c tetrose,pentose, hexose, heptose.

1.1.2.ng phn quang hc

Quy c Fischer: Fischer l ngi u tin nu ra nguyn tc biudin cc monosaccharide bng cng thc hnh chiu ca chng. Theo :hnh chiu ca cc nguyn t carbon bt i (C*) v cc nguyn t C khcnm trn mt ng thng, nguyn t C c s th t nh nht c hnh chiunm trn cng. Cn cc nhm th c hnh chiu bn phi hay bn tri.

V d : glyceraldehyde.V glyceraldehyde c 1 C* nn theo quy tc ca Vant Hoff c 2

ng phn (N = 2n)

1CHO 1CHO

HO- 2C* -H H-2C*-OH D: -OH bn phi

L: -OH bn tri

3CH2OH 3CH2OH

L glyceraldehyde D glyceraldehyde.

Khi phn t monosaccharide c nhiu C* th cng thc c dng Dhay L c cn c vo v tr nhm OH ca C* xa nhm carbonyl nht.

V d : CHO CHO

H-C-OH H-C-OH

HO-C-H HO-C-H

H-C-OH H-C-OH

H-C-OH HO-C-H

CH2OH CH2OH

D glucose L glucose




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Ch : monosaccharide t triose trlnu c C* tr dihydoxy aceton

CH2OH

C = O

CH2OH

1.1.3. Cng thc vng ca monosaccharide

Cng thc thng theo Fischer nh trnh by trn khng ph hpvi mt s tnh cht ho hc ca chng nh: mt s phn ng ho hcthng xy ra vi aldehyde khng xy ra i vi monosaccharide . V vy

c th nghrng nhm -CHO trong monosaccharide cn tn ti di dngcu to ring bit no .

Mt khc: monosaccharide c th to ether vi methanol to thnhmt hn hp 2 ng phn c cng nhm methoxy (- OCH3). iu chng t trong monosaccharide cn tn ti mt nhm -OH c bit.

Qua nghin cu Kolle cho thy: s ng phn thu c camonosaccharide thc t nhiu hn sng phn tnh theo cng thc N=2n, do gii thch cc hin tng trn, Kolle cho rng ngai dng thngmonosaccharide cn tn ti dng vng.

S to thnh dng vng xy ra do tc dng ca nhm -OH cngphn t monosaccharide to thnh dng hemiacetal hay hemiketal.




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V d : cu to vng ca glucose xy ra nh sau:

Do s to thnh hemiacetal vng m C1 trnn C*, nhm -OH mic to ra C1 l -OH glucoside. Tng t vi ketose th C2 trnn C*,nhm -OH mi c to ra C2 l -OH glucoside khi to thnhhemiketal.

Cch biu din cng thc vng nh trn da vo nguyn tc caHaworth: C v cu ni vi oxy nm trn mt mt phng , cc nhm thcng thc thng nm bn phi th cng thc vng nm di mt phng vngc li. Ring cc nhm th ca C c nhm OH dng to cu ni oxy ththeo quy tc ngc li.

1.1.4. Hin tng hbin ca monosaccharideNh ta thy, khng th gii thch c tt c cc tnh cht ca

monosaccharide nu ta ch tha nhn mt dng cu to no camonosaccharide. Nn ngi ta cho rng cc dng cu to c thchuyn ho ln nhau.

pyranose pyranose

Dng thng

Furanose Furanose




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1.1.5. Tnh cht ca monosaccharide

1.1.5.1. L tnh

Cc monosaccharide tan trong nc, khng tan trong dung mihu c, c tnh quay cc tr biose v khng c C*.

1.1.5.2. Ho tnh

a. Monose l tc nhn kh

Trong mi trng kim, kh cc ion kim loi nng c ho tr caothnh ion c ha tr thp hay cc ion kim loi thnh kim loi.

Tnh kh ny do nhm aldehyde hay nhm ketone to ra v ccmonose bin thnh acid.

V d: Cu2+

b bin i thnh Cu+

trong phn ng vi thuc thFehling, Ag+ b bin i thnh Ag trong phn ng trng gng.

b. Phn ng vi cc cht oxy ho

Tu thuc vo cht oxy ho:

- Cht oxy ho nh nh nc brom ng aldose s thnh aldonicacid, vi ketose phn ng khng xy ra.

- Cht oxy ho mnh nh HNO3m c c s oxy ho xy ra 2u cho ta di acid.

- Trng hp c bit nu ta bo v nhm -OH glucoside bngcch methyl ha hay acetyl ho trc khi oxy ho bng nc brom, snphm to thnh l uronic acid.

c. Phn ng vi cht kh

D dng vng chim t l rt ln trong thnh phn, dng thngchim t l nh nhng cho ta thy r tnh cht ca mt carbonyl thts. Khi b kh: monose s bin thnh polyalcohol.

d. Phn ng to furfural

Di tc dng ca acid m c, cc aldopentose to thnh furfuralv aldohexose bin thnh hydroxymethylfurfural. Cc sn phm ny khicho tc dng vi cc phenol cho mu c trng nh: naphthol cho vngmu tm (Molisch). y l phn ng phn bit ng vi cc chtkhc. Nu ng 5C s cho mu xanh cm thch vi orcinol (Bial).

e. Phn ng ester ho

Cc gc ru ca monose c khnng kt hp vi acid to thnh ester.

Cc ester phosphate thng gp l: Glucose-6-phosphate, fructose-6-phosphate...




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1.1.6. Cc monose quan trng

1.1.6.1. Pentose

1.1.6.2. Hexose

Cc hexose quan trng nh:

* Glucose: cn gi l dextrose v lm quay mt phng nh sngphn cc v pha phi.

Ph bin rng ri trong thc vt nht l trong qu nho, nn cn gi lng nho, trong mu ngi c 0.8 - 1,1 g/l, nhng ngi b bnh i ngc thn 2g/l. Cc disaccharide quan trng l saccharose, lactose, maltose vcc polysaccharide quan trng l tinh bt, glycogen. Ngi ta s dng glucosetrong y hc nh cht tng lc.

* D - Mannose: t gp trng thi t do, thng g p trongpolysaccharride v glucoside

* D - Galactose: l thnh phn ca lactose c trong sa cn gi lng no tu. Chng l thnh phn cu to ca raffinose, hemicellulose.pectine...

* D - Fructose cn gi l levulose v lm quay mt phng nh sngphn cc v pha tri.

Fructose cn gi l ng qu, c trng thi t do trong tri cychn v mt ong. Chng l thnh phn ca disaccharide saccharose. Trong cth ta cn thy dng ester vi phosphoric acid ng vai tr quan trng trongtrao i cht. Fructose c ngt rt ln, dng c ngt bng 1/3 dng .




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1.2. Oligosaccharide

1.2.1. Disaccharide

S to thnh disaccharide l do s kt hp ca 2 monose cng loihay khc loi nhlin kt glucosidic. Lin kt glucosidic c th c tothnh gia -OH glucoside ca monose ny vi -OH glucoside ca monosekia, hay gia mt nhm -OH glucoside ca monose ny vi -OH ( khngphi -OH glucoside) ca monose kia.

Disaccharide ch c tnh kh khi t nht mt trong 2 nhm -OHglucoside trng thi t do. Ngha l disaccharide s khng c tnh khkhi 2 nhm -OH glucoside lin kt vi nhau.

Cc disaccharide quan trng

* Maltose do 2 phn t- D-glucose lin kt vi nhau v tr C1 -C4 to thnh. Cng thc cu to:

Maltose c nhm -OH glucoside trng thi t do nn c tnh kh.Maltose c nhiu trong mm la v mch nha (maltum) nn gi n l maltose.

* Lactose (ng sa) do mt phn t D-galactose lin kt vimt phn t D- glucose v tr C1- C4.

* Saccharose do mt phn t D-glucose lin kt vi mt phn t D-fructose v tr C1-C2. Do n khng c tnh kh, cn gi l ngma v c nhiu trong ma. D b thy phn khi un nng.




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1.2.2. Trisaccharide

L oligosaccharide c cha 3 monosaccharide, ph bin trongthin nhin l raffinose. Cng thc cu to nh sau: -D-galactopyranosyl1-2 -D glucopyranosyl 1-2 -D fructofuranose. Do c cng thc nh trnnn khng c tnh kh oxy. D b thy phn, di tc dng ca fructofuranosidase s to thnh fructose v melobiose vi galactosidases to thnh galactose v saccharose.

1.3. Polysaccharide

Cn gi l glycan, ty thnh phn monose c trong polysaccharidengi ta chia chng ra lm: homopolysaccharide (ch cha mt laimonosaccharide) v heteropolysaccharide (c t nht 2 laimonosaccharide).


http://images.google.com.vn/imgres?imgurl=http://www.benbest.com/cryonics/Sucrose.gif&imgrefurl=http://www.benbest.com/cryonics/vitrify.html&h=250&w=250&sz=15&tbnid=7ovRpSbCGRYD-M:&tbnh=106&tbnw=106&hl=vi&start=14&prev=/images%3Fq%3Dsucrose%26s


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Polysaccharide ng vai tr quan trng trong i sng ng vt,thc vt. Mt s polysaccharide thng g p nh tinh bt, glycogen,cellulose...

1.3.1. Polysaccharide thc vt

1.3.1.1. Tinh bt

L polysaccharide d tr ca thc vt, do quang hp to thnh.Trong c v ht c t 40 n 70% tinh bt, cc thnh phn khc ca cyxanh c it hn v chim khong t 4 n 20%.

Tinh bt khng ha tan trong nc, un nng th ht tinh btphng ln rt nhanh to thnh dung dch keo gi l h tinh bt.

Tinh bt c cu to gm hai phn: amylose v amylopectin, ngoira cn c khong 2% phospho di dng ester. T l amylopectin/amylosecc i tng khc nhau l khng ging nhau, t l ny go np l lnhn go t.

*Amylose

Chim 15 n 25% lng tinh bt, do nhiu gc D- glucose linkt vi nhau thng qua C1-C4 to thnh mch thng khng phn nhnh.

Trong khng gian n cun li thnh hnh xon c v c gi bn vngnh cc lin kt hydro. Theo mt s ti liu trong amylose cn c cha

cc D- glucopyranose dng thuyn.

Amylose bt mu xanh vi iodine, mu ny mt i khi un nng,hin mu tr li khi ngui. Mt c trng ha l khc cn ch l n bkt ta bi ru butylic.




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Ht tinh bt trong lc lp amylose

*Amylopectin

Cu to do cc phn t D- glucose lin kt vi nhau, nhng cphn nhnh. Ch phn nhnh l lin kt C1-C6 glucosidic.




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1.3.1.2. Cellulose

c cu to bi nhng phn t D-glucose lin kt vi nhaubng lin kt 1-4 glucosidic.

Chng l thnh phn ch yu ca vch t bo thc vt. i vingi th cellulose khng c gi tr dinh dng v cellulose khng b thyphn trong ng tiu ha. Mt s nghin cu cho thy n c vai tr trongiu ha tiu ho. ng vt n c thy phn c cellulose nhenzymecellulase.

Cellulose khng tan trong nc, tan trong dung dch Schweitzer.Khi un nng vi H2SO4, cellulose s b thy phn thnh cc phn t

D-glucose.Cellulose c dng hnh si di, nhiu si kt h p song song vi

nhau thnh chm nhcc lin kt hydro, mi chm (micelle) cha khang60 phn t cellulose. Gia cc chm c nhng khong trng, khi ho gkhong trng ny cha y lignin v ta xem lp lignin ny nh l mt lpcement. Lignin l cht trng hp ca coniferylic alcohol

Cc gc -OH ca cellulose c th to ester vi acid v d: to nitrocellulose vi HNO3 , to acetyl cellulose vi CH3COOH.




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1.3.1.3. Hemicellulose

Tn gi chung cho lp polysaccharide thng i theo vi cellulose

trong thc vt. Hemicellulose khng tan trong nc, tan trong dung dchkim v thy phn bng acid d hn cellulose.

Khi b thy phn hemicellulose to thnh mt hn hp gm cchexose v pentose hay ch mt mnh hexose m thi. Trong hemicellulosekhi monose no chim a s th hemicellulose c tn tng ng vimonose :

Xylose chim a s th hemicellulose c tn l Xylan,

Arabinose chim a s th hemicellulose c tn l Araban,

Galactose chim a s th hemicellulose c tn l Galactan...

Xylan c nhiu trong rm r, trong mt s cquan ca thc vt,galactose c nhiu trong rm, g v cc loi ht.

1.3.1.4. Inulin

L polysacchride d tr ca thc vt c trng lng phn t

khong 5000-6000, do nhng phn t D- fructose lin kt vi nhau bnglin kt 1-2 v tn cng bng mt phn t saccharose. Inulin c tm thy

trong c thc dc khong 40%. Ngi ta x dng inulin sn xutfructose. xc nh inulin ngi ta thy phn n v xc nh bng phnng nh tnh Seliwanoff.

1.3.1.5. Pectin

L loi polysaccharide c nhiu trong qu , c v thn cy, thnhphn chnh l galacturonic acid c nhm -COOH b methyl ha. Ngi tas dng rng ri pectin trong sn xut keo.

1.3.2. Polysaccharide ng vt

1.3.2.1. Glycogen

L polysaccharide d trng vt c tm thy trong gan vc, hin nay cn tm thy trong mt s thc vt nh ng, nm.

C cu to ging amylopectin nhng phn nhnh nhiu hn, bthu phn bi phosphorylase ( c coenzyme l pyrydoxal phosphate), ct lin kt 1-6 cn enzyme debranching. Sn phm cui cng l cc phnt glucose-1-P.




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Pha ngoi glucose lin kt 1-6

Mch chnh ht glycogen t bo gan1.3.2.2. Hyaluronic acid

C cng thc cu to c lp li tn v sau:

Hyaluronic acid c trng lng phn t rt ln, c th ln nnhiu triu, hyaluronic acid rt ph bin v l thnh phn quan trng cam lin kt, c tm thy trong dch khp xng, trong thy tinh th mt,n tc dng nh mt lp cement bo v bn trong t bo chng li sxm nhp ca vi khun cng nh cc cht l khc. khp xng n lm




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cho dch c tnh trn gip cng khi bau. Hyaluronic acid b thy phn bi hyaluronidase, enzyme ny c tm thy trong vi khun gybnh, trong tinh trng. Hyaluronidase to d dng cho tinh trng i vonon ca bun trng, mt khc n cng l yu t gip cho cc cht khcv vi khun gy bnh i vo cc m trong cth.

1.3.2.3. Chondroitin

L heteropolysaccharide, thnh phn khng th thiu c mxng sn.

1.3.2.4. Heparin

Heteropolysaccharide c tc dng chng li sng mu v ngnchn s bin i prothrombin thnh thrombin.

GlcA2S hoc IdoA2S

1.3.3. Mt spolysaccharide phbin khc

1.3.3.1. Chitin

L homopolysaccharide, c v s, c, cc loi cn trng v nm mc. N c cu to nh sau:




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1.3.3.2. Dextran

c tm thy vi khun v nm men, cu to mch chnh l D-glucose1-6, nhnh l 1-3 v thnh thong c nhnh 1-2 hay 1-4. Doc cu to 1-6 nn i vi ng vt, dextran khng b phn gii hay bphn gii rt chm.




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Dextran c di v hnh dng ging albumin, ngi ta thngdng nhit thy phn khng hon ton dextran nhm thay th proteinca huyt tng , dung dch 10% ca n hon ton trong sut. Trong cngngh ngi ta tng hp dextran v c gi l sephadex s dng trongtch tng phn protein.

TI LIU THAM KHO

Ti liu ting Vit1. Phm Th Trn Chu, Trn thi ng. 1999. Ho sinh hc, NXB Gio dc,H Ni.

2. Qu Hai. 2004. Gio trnh Ha sinh i cng, Ti liu lu hnh nib Trng HKH Hu.

3. Trn Thanh Phong.2004. Gio trnh Ha sinh i cng, Ti liu luhnh ni b Trng HKH Hu.

4. L Ngc T (ch bin), L Vn Ch, ng Th Thu, Phm Quc ThngNguyn Th Thnh, Bi c Hi, Lu Dun, L Don Din, 2000. Ha sinhCng nghip, Nxb KH&KT, H Ni.

Ti liu ting Anh1. Gilbert H. F. 1992. Basic concepts in biochemistry, Copyright by theMcgraw- Hill companies, Inc.

2. Lehninger A. L. 2004. Principles of Biochemistry, 4th Edition. W.HFreeman.




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Chng 2

Lipid

Cng nh saccharide, protein, lipid l cht hu cphc tp, ta cthnh ngha nh sau:

* nh ngha rng: Lipid l cht tan c trong dung mi hu c,khng tan trong nc, nh ngha ny khng phn nh ht tnh cht cacc lipid v:

- C lipid khng tan c trong dung mi hu cnh phospholipidkhng tan trong aceton.

- Nhng cng c cht khng phi lipid nhng tan c trong dungmi hu c.

* nh ngha hp: Lipid l ester ca ru v acid bo. Tuy nhinc nhng lipid do acid bo lin kt vi ru bng lin kt peptide.

* nh ngha dung ho: Lipid l nhng cht chuyn ho ca acidbo v tan c trong dung mi hu c.

Lipid rt ph bin ng vt cng nhthc vt v tn ti di 2dng mnguyn sinh cht (dng lin kt) v dng d tr (dng t do).

- Mnguyn sinh cht: thnh phn ca mng t bo cng nh ccbo quan khc v d: ty th, lp th... dng ny khng b bin i ngay ckhi con ngi b bnh bo ph hoc bi.

- Dng d tr (dng t do) c tc dng cung cp nng lng cho cth, bo v cc ni quan, l dung mi cn thit cho mt s cht khc.

Cn c vo thnh phn nguyn t c mt, ngi ta chia lipid ra lm 2 loi

* Lipid n gin: trong phn t ch cha C, H, O.

* Lipid phc tp: ngoi C, H, O cn c mt s nguyn t khc

nh N, P, S.

2.1. Lipid n gin2.1.1. Glycerid

Glycerid l ester ca ru glycerol v acid bo, l md tr phbin ng vt v thc vt.




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1- Stearoyl, 2- linoleoyl, 3-palmitoyl glycerol,

mt triacylglycerol hn tp

2.1.1.1. Glycerol

L triol khng mu, v ngt nhn. Khi t glycerol hay lipid ccha glycerol vi cht ht nc s to acrolein c mi kht.

2.1.1.2. Acid bo

Acid bo thng gp l nhng acid bo c s carbon chn, mch

thng, c th no hay khng no v chui C xp theo hnh ch chi.Tuy nhin cng c nhng acid bo ngoi nhm chc acid cn cha

nhng nhm chc khc nh ru, ketone, mch carbon c vng hay nhnh.

a. Acid bo chn, thng, no: CH3(CH2)nCOOH

C4 CH3 -(CH2)2 COOH butylic acid c nhiu trong c.

C6 CH3 -(CH2)4 -COOH caproic acid c trong b, sa d.

C8 CH3 - (CH2)6-COOH caprylic acid c trong b, sa d.

C10 CH3-(CH2)8 COOH capric acid c trong b, sa d.




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C12 n=10 lauric acid c trong du da.

C14 n=12 myristic acid c trong du da.

C16 n=14 palmitic acid c trong du ng vt,thc vt.C18 n=16 stearic acid c trong du ng vt,thc vt.

C20 n=18 arachidic acid c trong du lc.

b. Acid bo chn, thng, khng no

- Cha mt ni i (C): 10 9

C16 (9-10): CH3-(CH2)5 -CH = CH- (CH2)7COOHPalmitoleic acid : Tm thy trong du thc vt.

C18 (9-10): CH3-(CH2)7 -CH = CH- (CH2)7 COOH

Oleic acid: acid ny c ba ng phn.C18 (6-7): Petroselenic acid

C18 (11-12): Vaccenic acid.

C18 (12-13): Heparic acid

- Acid bo c 2 ni i (C):

C18 (9-10,12-13): Linoleic acid

CH3-(CH2)4 -CH = CH- CH2-CH=CH-(CH2)7-COOH

C th khng tng hp c acid ny m ly t ngoi vo. Ngyxa ngi ta quan nim acid ny l vitamin v gi l vitamin S. Nhngthc cht l mt acid bo m cth cn vi mt lng ln.

- Acid bo c cha 3 ni i (C):

C18((9-10,12-13,15-16): Linolenic acid, c th khng tng hpc acid ny.

- Acid bo c 4 ni i (C):

C20 (5-6,8-9,11-12,14-15): Arachidonic acid.

Ngoi ra cn c cc acid bo c cha ni ba nhng khng quan trng.

c. Acid bo c cha chc ru

Thng gp trong lipid phc tp v cha nhm ru gn chc acidnn c tn l - hydroxy...

R-CH-COOH

OH




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V d: - hydroxy lynoceric acid CH3 -(CH2 )21- CH-COOH

OH

Ricinoleic acid

CH3-(CH2)5 - CH - CH2 - CH = CH- (CH2)7 - COOH10 9

OH

d. Gc R trong phn t acid c nhnh v c s C l

Phocenic acid: CH3

CH3

CH CH2 COOH

Undecylonic acid : CH2 = CH - (CH2)8 - COOH

e. Acid bo c vng

* Chaulmoogric acid: - (CH2)12 - COOH

* Sfe C

rculic acid: H3 - CH2 - C = C - (CH2)7 - COOH

CH2

2.1.1.3. Tnh cht ca acid bo v triglyceride* Tnh cht vt l:

a. im tan chy

im tan chy ph thuc vo s C ca acid bo, acid bo c chuiC di th im tan chy cao v ngc li. Nhng acid bo c C l c imtan chy thp hn acid bo c s C nh hn n 1 n v . Ngoi ra tanchy cn ph thuc vo s ni i trong phn t acid bo, acid bo chanhiu ni i th im tan chy cng thp.

b. siAcid bo c chui C di th si cng cao, thng p dng tnh

cht ny tch cc acid bo ra khi nhau.

c. Tnh ho tan

- Trong nc: acid bo c chui C ngn (4,6,8) d tan, C10 kh tan,C12 khng tan. Nu acid bo dng mui th d ha tan hn.

- Trong dung mi hu khng phn cc nh benzen, ether, etherdu ho acid bo d tan.




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- Trong dung mi hu c phn cc nh aceton, acid bo kh hotan hay ho tan rt t.

* Tnh cht ho hc:a. S hydrogen ho

Acid bo cha no c th kt hp vi H2 to thnh acid bo no

R - (CH2)n - CH =CH- (CH2)n - COOH + H2

R - (CH2)n -CH2 - CH2 - (CH2)n - COOH

Ngi ta dng phn ng ny ch to thc phm nh margarin.

b. S halogen ho

Acid bo khng no kt hp vi cc nguyn t thuc h halogen (F,

Cl, Br, I) to thnh acid bo no.R - (CH2)n - CH = CH- (CH2)n - COOH + I 2

R - (CH ) - CH - CH- (CH2)n - COOH2 n

I I

C th dng phn ng ny xc nh s ni i trong phn tacid bo. Phn ng d dng hay kh xy ra tu thuc vo v tr ni i ivi nhm carboxyl, ni i cng gn nhm carboxyl phn ng cng khxy ra.

xc nh s ni i ngi ta cn c vo ch s Iod.ChsIod:Lsgam Iod cn thit tc dng ln 100gam cht

bo. Do ch s iod cng ln th s ni i cng nhiu.

c. S thu phn:

Ester nn khi thu phn s to thnh ru glycerol v acid bo.Tc nhn thy phn l acid, kim, nc hay enzyme.

* Thy phn bng nc cn nhit v p sut cao.

* Thy phn bng kim: NaOH hay KOH

Chsx phng ho:smg KOH cn thittrung ho 1g cht boDo ch s x phng cng ln th di mch cng ngn, nn

c dng xc nh di ca mch C.

xc nh tnh cht ca cht bo ngi ta cn cn c vo mt sch s khc nh ch s acid.

Chsacid:smg KOH dng trung ho tt c acid bo tdoctrong 1g cht bo.




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* Thu phn bng enzyme: trong c th lipid b thu phn bngenzyme lipase.

- Lipase dch trng tc dng vo v tr .- Lipase ty tng tc dng vo v tr v .

d. S i ha:

Du m lu c mi v v kh chu gi l s i ha, mt trongnhng nguyn nhn gy ra l do oxy khng kh kt h p vo ni i tothnh peroxide. Nu oxy kt hp vo nguyn t carbon ng cnh lin kti th s to thnh hydrogen peroxide. Sau peroxide v hydrogenperoxide s b phn gii to thnh aldehyde v ketone. Cc aldehyde vketone ny u l nhng cht c mi v v kh chu.

2.1.2. Cerid

Cng l ester ca ru v acid bo, nhit thng th rn, c ng thc vt, thc vt n thng to thnh mt lp mng ph ln l,thn, qu ca cy. Cng thc tng qut:

R O CO R

Ru trong cerid l ru cao phn t, ch cha mt nhm OH ,mnh C khng phn nhnh, rt t khi mch C c vng V d: Rucetol:CH3 - (CH2)14-CH2OH.

Sp ong, sp c voi (spermaceti) l ester ca ru cetol vpalmitic acid.

Ngoi ra trong sp ong v sp c voi cn c ru t do, acid bot do v hydrocarbon.

2.1.3. Sterid

L ester ca ru sterol v acid bo. Ru sterol c vng v trnglng phn t rt ln, sterol tiu biu l cholesterol, acid mt. Acid bothng l palmitic, oleic, ricinoleic.




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2.1.3.1.Cholesterol

Cholesterol bao gm nhn phenanthrene kt hp vi cyclopentan

to thnh cyclopentanoperhydrophenanthrene. Cholesterol c mang nhmru C3, ni i C5 - C6 v 2 gc CH3 C10, C13 v mt nhnhisooctan C17.

Cholesterol ch c ng vt, trong mu c khong 2.10-3, cnhiu trong c, nhng m l lch, gan, da cng c cha cholesterol haycc cht chuyn ho ca n. Cholesterol c tm thy u tin sn mt,sn mt l do s dn mt n rut non b nghn, mt cha nhiucholesterol nn kt ta li thng sn mt. Cholesterol l cht quan trngtrong s sinh tng hp acid mt, vitamin D v nhiu cht khc.

Cholesterol + acid bo cholesterid

Trong thin nhin, cc sterol trng thi t do nhiu hn trngthi sterid. cth ngi, ch 10% sterol b ester ha to thnh sterid. Tl sterol v sterid cc m khc nhau l khng ging nhau.

* L tnh ca cholesterol: kt tinh di dng vy ng nh nh xc, dng kt tinh cng khc nhau tu theo mi trng kt tinh.

* Ho tnh:

- Phn ng vi acid bo do nhm -OH C3.

- B hydrogen ha hay halogen ho C5 - C6.




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- Phn ng mu:

+ Phn ng Liebermann: Cholesterol cho mu xanh lc, mu ny

rt bn trong nhiu gi, phn ng ny c dng xc nh cholesterol bnh vin.

+ Phn ng Salkowski: Cholesterol cho vnh mu .

2.1.3.2. Acid mt:

Acid mt c tm thy trong ng vt c v gm 3 dng sau:cholic acid, deoxycholic v chenodeoxycholic acid.

Acid mt l cht c i vi ngi. V vy trong mt, acid mt lin ktvi acetamin to thnh mt cht t c hn.

Ngoi cholesterol v acid mt cn c cc sterol khc cng cngun gc ng vt nh hormone nang thng thn, hormone tuyn sinhdc, cc sterol c ngun gc thc vt nh ergosterol, stigmasterol...

2.2. Lipid phc tp

Khc vi lipid t do c nhim v cung cp nng lng , hm lnglun thay i. Lipid phc tp c nhim v tham gia xy dng cc cu tca t bo, hm lng khng thay i hay rt t thay i.

2.2.1. Glycerophospholipid (phosphatid)

Chng ta c th hnh dung cu to chung ca glycerophospholipid nh sau:

Glycerophospholipid l diester ca phosphoric acid. Mt phaphosphoric acid lin kt vi glycerol, pha kia lin kt vi X. Ty cu toca X ta c cc loi glycerophospholipid khc nhau:




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Lecithin: Lc X l choline nn lecithin cn c gi l cholinephosphatid

Lecithin c nhiu trong lng trng g, trong u nnh, trongmu, trong cc dy thn kinh. Qua cu to ta nhn thy n gm 2 phn

- Phn phn cc bao gm phosphoric acid v base nitrogen a nc.




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- Phn khng phn cc bao gm cc gc acid bo, ru glycerolght nc.

Do c cu to nh trn nn lecithin trong nc s to thnh dungdch gi l dung dch gi.

Nh c tnh va a nc, va ght nc m hnh nh phospholipid tham gia trong vic bo m tnh thm mt chiu ca ccmng cu trc di t bo.

Lecithin c th b thu phn bng acid, kim hay enzyme:

* Thu phn bng acid: tt c lin kt esteru b ct t.

* Thu phn bng kim: ta c acid bo dng mui,glycerophosphate v choline. Nhng choline b phn hy cho

trimetylamin. Vi kim nh ch c th ct lin kt ester gia ru v acidbo.

* Thu phn bng enzyme: c 4 loi enzyme lecithinase A, B, C vD tc ng ln cc lin kt ester khc nhau:

B

CH2O - CO - R1

A

CHO - CO - R2C

OH

CH2O - PO D

Lecithinase A ct lin kt v tr ca lecithin cho acid bo vlisolecithin.

Cephalin: Trong cu to ca cephalin X l colamine.

CH2O-CO-R1

CHO-CO- R2O

CH2O-P = O

O-CH2- CH2 -H3N+




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Tng t lecithin, cephalin (X l ethanolamine) c cu tao gm hai

phna nc v ght nc, l thnh phn ca dy thn kinh v c nhiu trong no.Lisocephalin c to thnh khi ct lin kt esterv tr , cngc tnh cht ph hy hng cu nh lisolecithin.

Serinphosphatid: Gi l serinphosphatid khi X l serine.

Trong c th: lecithin, cephalin, serinphosphatid thng gp dng hn hp bi c s bin i tng h gia serine, choline vcolamine.

2.2.2. Sphingophospholipid

y l lipid phc tp, trong ru a nguyn t l sphingosine.Acid bo lin kt vi ru sphingosine bng lin kt peptid. Ty theo X tac cc loi sphingophospholipid khc nhau

Acid bo

Sphingophospholipid quan trng nht l sphingomyelin, y X

l: phosphocholine. Acid bo trong sphingomyelin l lignoceric, palmitic,




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stearic hay nervonic. Sphingophospholipid l diaminophospholipid, khcvi phosphatid l monoaminophospholipid.

Sphingophospholipid khng tan trong ethylic ether, da vo tnhcht ny tch chng ra khi hn hp lipid

2.2.3.Glycolipid

Glycolipid l lipid phc tp khng cha phospho, trong thnh phnca chng c cha hexose, thng l galactose hay cc dn xut cagalactose, i khi l glucose. Thuc nhm ny c MGDG, DGDG vsulfolipid kh ph bin trong lc lp v cc thnh phn khc ca t bo l.

6-Sulfo-6-deoxy--D-glucopyranosyldiacyglycerrol(sulfolipid)

2.2.4. Sphingolipid

Cerebroside: trong phn t cerebroside ru sphingosine lin ktvi acid bo bng lin kt peptide, vi galactose (X) bng lin ktglucosidic.




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Cc cerebroside khc nhau v thnh phn acid bo, c nhiu trongm thn kinh, hng cu, bch cu, tinh trng

Ganglyoside: cu to ging cerebroside nhng X l phc hpoligosaccharide

TI LIU THAM KHOTi liu ting Vit

1. Phm Th Trn Chu, Trn thi ng. 1999. Ho sinh hc, NXB Gio dc,H Ni.

2. Qu Hai.2004. Gio trnh Ha sinh i cng, Ti liu lu hnh nib Trng HKH Hu.

3. Trn Thanh Phong.2004. Gio trnh Ha sinh i cng, Ti liu luhnh ni b Trng HKH Hu.

4. L Ngc T (ch bin), L Vn Ch, ng Th Thu, Phm Quc ThngNguyn Th Thnh, Bi c Hi, Lu Dun, L Don Din, 2000. Ha sinhCng nghip, Nxb KH&KT, H Ni.

Phc hpologosaccharide

Acid bo

Ti liu ting Anh1. LehningerA.L. 2004. Principles of Biochemistry, 4th Edition. W.HFreeman.

2. Mead, Alfin-Slater, Howton & Popjk. 1986. Lipids: Chemistry,biochemistry and nutrion, Plenum, New York.




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Chng 3

Protein

Protein l hp cht hu cc ngha quan trng bc nht trong cth sng, v mt s lng, protein chim khng di 50% trng lng khca t bo; v thnh phn cu trc, protein c to thnh ch yu t ccamino acid vn c ni vi nhau bng lin kt peptide. Cho n nayngi ta thu c nhiu loi protein dng tinh th v t lu cng nghin cu k thnh phn cc nguyn t ho hc v pht hin c

rng thng thng trong cu trc ca protein gm bn nguyn t chnh lC, H, O, N vi t l C 50%, H 7%, O 23% v N 16%. c bit tl N trong protein kh n nh (li dng tnh cht ny nh lngprotein theo phng php Kjeldahl bng cch tnh lng N ri nhn vi6,25). Ngoi ra trong protein cn gp mt s nguyn t khc nh S 0-3%v P, Fe, Zn, Cu...

Phn t protein c cu trc, hnh dng v kch thc rt a dng,khi lng phn t (MW) c tnh bng Dalton (1Dalton = 1/1000 kDa,c l kiloDalton) ca cc loi protein thay i trong nhng gii hn rtrng, thng thng t hng trm cho n hng triu. v d: insulin c khilng phn t bng 5.733; glutamat-dehydrogenase trong gan b c khilng phn t bng 1.000.000, v.v...

T lu ngi ta bit rng protein tham gia mi hot ng sngtrong cth sinh vt, t vic tham gia xy dng t bo, m, tham gia hotng xc tc v nhiu chc nng sinh hc khc. Ngy nay, khi hiu r vaitr to ln ca protein i vi cth sng, ngi ta cng thy r tnh chtduy vt v ngha ca nh ngha thin ti ca Engels P. Sng l phng

thc tn ti ca nhng th protein. Vi s pht trin ca khoa hc, vai trv ngha ca protein i vi s sng cng c khng nh. Cng vinucleic acid, protein l csvt cht ca s sng.

3.1. Amino acid

3.1.1 Cu to chung

Amino acid l cht hu c m phn t cha t nht mt nhmcarboxyl (COOH) v t nht mt nhm amine (NH2), tr proline ch cnhm NH (thc cht l mt imino acid).




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Trong phn t amino acid u c cc nhm COOH v NH2 gn vicarbon v tr . Hu ht cc amino acid thu nhn c khi thu phn

protein u dng L- amino acid. Nh vy cc protein ch khc nhau mch nhnh (thng c k hiu: R).

Hnh: 3.1. Cng thc cu to chung ca cc amino acid

3.1.2. Phn loi amino acid

Hin nay ngi ta phn loi amino acid theo nhiu kiu khc nhau,mi kiu phn loi u c ngha v mc ch ring. Tuy nhin, huda trn cu to ho hc hoc mt s tnh cht ca gc R. V d c ngichia cc amino acid thnh 2 nhm chnh l nhm mch thng v nhmmch vng.

Trong nhm mch thng li tu theo s c mt ca s nhmcarboxyl hay s nhm amine m chia ra thnh cc nhm nh, nhm aminoacid trung tnh (cha mt nhm COOH v mt nhm NH2); nhm aminoacid kim (cha mt nhm COOH v hai nhm NH2); nhm amino acidacid (cha hai nhm COOH v mt nhm NH ).2

Trong nhm mch vng li chia ra thnh nhm ng vng hay dvng v.v...

C ngi li da vo tnh phn cc ca gc R chia cc amino acidthnh 4 nhm: nhm khng phn cc hoc k nc, nhm phn ccnhng khng tch in, nhm tch in dng v nhm tch in m.

Tuy nhin, hin nay cch phn loi cc amino acid ang cnhiu ngi s dng nht l da vo gc R ca amino acid v c chialm 5 nhm:

Nhm I. Gm 7 amino acid c R khng phn cc, k nc, l:glycine, alanine, proline, valine, leucine, isoleucine v methionine. (Hnh 3.2)




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Hnh 3.2. Cng thc cu to ca cc amino acid nhm I

Nhm II. Gm 3 amino acid c gc R cha nhn thm, lphenylalanine, tyrosine v tryptophan (Hnh 3.3.)

Hnh 3.3. Cng thc cu to ca cc amino acid nhm II




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Nhm III. Gm 5 amino acid c gc R phn cc, khng tch in, l serine, theonine, cysteine, aspargine v glutamine (Hnh 3.4)

Hnh: 3.4. Cng thc cu to ca cc amino acid nhm III

Nhm IV. Gm 3 amino acid c R tch in dng, l lysine,histidine v arginine, trong phn t cha nhiu nhm amin (hnh 3.5).

Hnh 3.5. Cng thc cu to cc amino acid nhm IV




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Nhm V. Gm 2 amino acid c gc R tch in m, l aspartatev glutamate, trong phn t cha hai hm carboxyl (hnh 3.6).

Hnh 3.6. Cng thc cu to ca cc amino acid nhm V

3.1.3. Cc amino acid thng gp

Cc amino acid thng g p l nhng amino acid thng c mttrong thnh phn ca cc loi protein. Chng c khong 20 loi v cthu nhn khi thu phn protein. Cc loi amino acid ny c tn gi, khilng phn t v k hiu c trnh by trn bng 3.1.

3.1.4. Cc amino acid khng ththay th

Cc amino acid c hnh thnh bng nhiu con ng khc nhau.

Nh bit, trong phn t protein c khong 20 loi amino acid, tuy nhintrong cth ngi v ng vt khng tng hp c tt c cc loi mphi a t ngoi vo qua thc n. Nhng amino acid phi a t ngoivo c gi l cc amino acid khng th thay th. Ngi ta bit c ckhong 8-10 loi amino acid khng th thay th bao gm: Met, Val, Leu,Ile, Thr,Phe, Trp, Lys, Arg v His v ngy nay ngi ta cn xem Cys cngl mt amino acid khng th thay th.

3.1.5. Cc amino acid t gp

Ngoi cc amino acid thng gp trn, trong phn t protein ikhi cn c mt s amino acid khc, l nhng loi t g p. Cc aminoacid ny l dn xut ca nhng amino acid thng gp nh: trong phn tcollagen c cha 4-hydroxyproline l dn xut ca proline, 5-hydroxylysine l dn xut ca lysine v.v...Mt khc, mc d khng ctrong cu trc protein, nhng c hng trm loi amino acid khc cng cth tn ti dng t do hoc lin kt vi hp cht khc trong cc m v t




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bo, chng c th l cht tin thn hay l cc sn phm trung gian ca qutrnh chuyn ho trong cth.

Bng 3.1. Cc amino acid thng gpTn amino

acid

Tn amino acid gi theo danhphp ho hc

Tn

vit ttK

hiuKhi lng

(MW)

Glycine Gly G 75-aminoacetic acidAlanine Ala A 89-aminopropionic acid

Proline Pro P 115-pyrolydilcarboxylic acid

Valine Val V 117-aminoisovaleric acid

Leucine Leu L 131-aminoisocaproic acid

Isoleucine Ile I 131-amino--metylvaleric acid

Methionine Met M 149-amino--metylthiobutyric acid

Phenylalanine Phe F 165-amino--phenylpropionic acid

Tyrosine Tyr Y 181-amino--hydroxyphenylpropionic acid

Tryptophan Trp W 204-amino--indolylpropionic acid

Serine Ser S 105-amino--hydoxypropionic acid

Threonine Thr T 119-amino--hydroxybutiric acidCysteine Cys C 121-amino--thiopropionic acid

Aspargine amid ca aspartate Asn B 132

Glutamine amid ca glutamate Gln Q 146

Lysine Lys K 146, diaminocaproic acid

Histidine His H 155-amino--imidazolpropionic acid

Arginine Arg R 174-amino--guanidinvaleric acid

Aspartate Asp D 133-aminosuccinic acidGlutamate Glu E 147-aminoglutarate

3.1.6. Mt stnh cht ca amino acid

3.1.6.1. Mu sc v mi v ca amino acid

Cc amino acid thng khng mu, nhiu loi c v ngt kiung nh glycine, alanine, valine, serine, histidine, tryptophan; mt sloi c vng nh isoleucine, arginine hoc khng c v nh leucine. Bt




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ngt hay cn gi l m chnh l mui ca natri vi glutamic acid(monosodium glutamate).

3.1.6.2. Tnh tan ca amino acidCc amino acid thng d tan trong nc, cc amino acid u kh

tan trong alcohol v ether (tr proline v hydroxyproline), chng cng dho tan trong acid v kim long (tr tyrosine).

3.1.6.3. Biu hin tnh quang hc ca amino acid

Hnh 3.7. ng phn lp th ca alanine

Cc amino acid trong phn t protein u c t nht mt carbon bti (tr glycine) v th n u c biu hin hot tnh quang hc, nghal c th lm quay mt phng ca nh sng phn cc sang phi hocsang tri. Quay phi c k hiu bng du (+), quay tri c khiu bng du (-). Gc quay c hiu ca amino acid ph thuc vo

pH ca mi trng.Tu theo s sp xp trong cu trc phn t ca cc nhm lin kt

vi carbon bt i m cc amino acid c cu trc dng D hay L (hnh 3.7)gi l ng phn lp th. Sng phn lp thc tnh theo 2n (n l scarbon bt i)

Hu ht cc amino acid khc hp th tia cc tm bc sng ()khong t 220 - 280 nm. c bit cng nng 10-3M, trong bc sngkhong 280 nm, tryptophan hp th nh sng cc tm mnh nht, gp 4 lnkh nng h p th ca tyrosine (hnh 3.8) v phenylalanine l yu nht.




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Phn ln cc protein u cha tyrosine nn ngi ta s dng tnh cht nynh lng protein

hp ph

- Bc sng(nm)Hnh 3.8. Ph hp th nh sng cc tm ca tryptophan v tyrosine

3.1.6.4. Tnh lng tnh ca amino acid

Trong phn t amino acid c nhm carboxyl -COOH nn c khnng nhng proton (H+) th hin tnh acid, mt khc c nhm amin- NH2nn c kh nng nhn proton nn th hin tnh base. V vy amino acid ctnh cht lng tnh.

Trong mi trng acid, amino acid dng cation (tch indng), nu tng dn pH amino acid ln lt nhng proton th nhtchuyn qua dng lng cc (trung ho vin), v tip tc tng pH aminoacid s nhng proton th hai chuyn thnh dang anion (tch in m). Vvy i khi ngi ta coi n nh mt di-acid.

cation lng cc anionHnh 3.9. Tnh lng tnh ca amino acid




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Tng ng vi phn ly H+ ca cc nhm COOH v NH3+ c cc

tr s pK1 v pK2 (biu th phn ly ca cc nhm c 1/2). T trctin chuyn sang dng lng tnh v sau cng chuyn thnh dng anion.

phn ly ca H+

Hnh 3.10. ng cong chun ca glycine nng 1 M 25OC

Ngi ta xc nh c pH (pI= pH ng in) = pK + pKi 1 2 / 2. Vd khi ho tan glycine vo mi trng acid mnh th hu nh glycine udng cation. Nu tng dn lng kim, thu c ng cong chun .Trn ng cong chun thy rng glycine ln lt nhng 2 protontrc Tng ng phn ly ca nhm COOH c mt na c tr spK += 2,34 v phn ly ca NH c mt na c tr s pK1 3 2= 9,60. Nhvy ta c

2,34 + 9,60

pHi = = 5,97

2




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Bng: 3.2 Cc tr s pK ca cc amino acid thng gp

Cc tr s pK pITn cc

amino acid +pK (ca COOH) pK (ca NH ) pK 1 2 3 R (ca R)

5,979,602,34Glycine

6,019,602,34Alanine

6,4810,961,99Proline

5,979,622,32Valine

5,989,602,36Leucine

6,029,682,36Isoleucine

5,749,212,28Methionine

5,489,131,83Phenylalanine5,6610,079,112,20Tyrosine

5,899,392,38Tryptophan

5,689,152,21Serine

5,879,622,11Theonine

5,078,1810,281,96Cysteine

5,418,802,02Aspargine

5,659,132,17Glutamine

9,7410,538,952,18Lysine7,596,009,171,83Histidine

10,7612,489,042,17Arginine

2,773,659,601,88Aspartate

3,224,259,672,19Glutamate

Mt khc ti pK1 + 2 s phn ly H+ -ca nhm COO glycine l

99%, ch 1% dng COOH v pK +-2 dng NH2 3 l 99%, ch 1% dng

NH . Nh vy trong vng pH t pK + 2 n pK2 1 2 -2, phn t glycine chyu dng lng tnh v kt qu ta c mt vng ng in. Ngoi ra ccamino acid trong gc R c thm nhm COOH hay NH2 s phn ly cachng s c thm mt tr s phn ly na-pKR(xem bng 3.2).

3.1.7. Cc phn ng ho hc ca amino acid

Cc amino acid u c nhm NH v COOH lin kt vi C2 , v vychng c nhng tnh cht ho hc chung. Mt khc cc amino acid khcnhau bi gc R, v vy chng c nhng phn ng ring bit. Ngi ta chiacc phn ng ho hc ca amino acid thnh 3 nhm:




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- Phn ng ca gc R

Do cc amino acid c cu to gc R khc nhau, nn ngi ta c th

dng xc nh tng amino acid ring r nhphn ng c trng ca n,v d phn ng oxy ho kh do nhm SH ca cysteine, phn ng to muido cc nhm COOH hay NH2 ca glutamate hay lysine, phn ng toester do nhm OH ca tyrosine v.v...

- Phn ng chung

L phn ng c s tham gia ca c hai nhm - COOH v - NH2.Tt c cc amino acid trong phn t protein u phn ng vi h p chtninhydrin to thnh phc cht mu xanh tm, ring imino acid nh proline tothnh mu vng. Phn ng c thc hin qua mt s bc nh sau:

Di tc dng ca ninhydrin nhit cao, amino acid to thnhNH3, CO2 v aldehide, mch polypeptide ngn i mt carbon; ng thininhydrin chuyn thnh diceto oxy hindriden. Diceto oxy hindriden, NH3 mito thnh tip tc phn ng vi mt phn t ninhydrin khc to thnh phccht mu xanh tm (hnh 3.11)

Hnh 3.11. Phn ng ca protein vi ninhydrin

- Phn ng ring bit

C th chia cc phn ng ring bit theo hai nhm- COOH v- NH2+ Cc phn ng ca nhm - COOH. Ngoi cc phn ng ca

nhm COOH thng thng to ester, to amid, to mui ...th n cn cnhng phn ng c trng khc nh c th b kh thnh h p cht ruamino di s xc tc ca NaBH4.

R-NH CH-COOH R-NH CH-CH OH2 2 2 Nhm COOH c th to thnh phc aminoacyl-adenylate trong

phn ng hot ho amino acid tng h p protein, hay c th loi CO2vn gp rt nhiu trong qu trnh thoi ho amino acid.




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+ Cc phn ng ca nhm - NH2. Nhiu phn ng ca nhm aminec dng nh tnh v nh lng cc ch tiu ca amino acid nh:

nh lng nitrogen ca amino acid ngi ta cho phn ng viHNO gii phng N2 2.

R-CH-COOH R-CH-COOH

+ HNO OH + NNH + H O2 2 2 2

nh lng amino acid ngi ta cho phn ng vi aldehyde tothnh base schiff.

xc nh amino acid u N-tn cng ngi ta cho tc dng vi

2-4 dinitrofluobenzen (phn ng Sanger) hay phenyliothiocyanate (phnng Edman).

3.2. Peptide

3.2.1. Khi nim chung

Peptide l nhng protein thng c cu trc on ngn khong t hain vi chc amino acid ni vi nhau, c khi lng phn t thng di6.000. Chng c thc tng hp trong t nhin hoc c hnh thnh do sthoi ho protein. Trong cc peptide cc amino acid c lin kt vi nhauthng qua lin kt peptide (hnh 3.12).

Hnh 3.12. Sto thnh lin kt peptide

Lin kt peptide c bn cao bi cu trc ca n c 4 e', 2e'thuc v lin kt C=O cn 2e' thuc v bi e' t do ca nguyn t N.Lin kt gia C-N l lin kt phc t p, n c th chuyn t dng n




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dng lai (trung gian) th b mt phn ghp i ca lin kt (hnh 3.13).Ngi ta cho rng t l ca lin kt kp ny l khong 30% i vi linkt C-N v 70% vi lin kt gia C v O. Nh vy u ca mt chuipeptide l amino acid c nhm -amine (-NH2) t do c gi l u N-tn cng v u kia c nhm - carboxyl ( -COOH) t do c gi lu C tn cng. Lin kt peptide to nn b khung chnh ca chuipolypeptide, cn cc gc R to nn mch bn ca chui (hnh 3.14)

Dng cng ho tr Dng ion +

Dng lai (hybrid)

Hnh 3.13. Stn ti cc dng ca lin kt peptide

M ch chnh

M ch bnHnh 3.14. Mch bn v khung ca mt chui polypeptide

3.2.2. Cc phng php xc nh peptide

Ngoi phn ng ca nhm NH2 v COOH u tn cng, cc gc Rca peptide cng cho nhng phn ng mu c trng ca cc amino acidt do tng ng. Mt trong nhng phn ng mu c trng nht dnh cholin kt peptide l phn ng Biure, phn ng ny khng xy ra vi




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amino acid t do v vi dipeptide. Trong mi trng kim mnh, lin ktpeptide phn ng vi CuSO4 to thnh phc cht mu tm (hnh 3.15.)

v c kh nng hp th cc i bc sng 540 nm.y l phn ng c s dng rng ri nh lng protein.Phng php xc nh protein theo Lowry cng da trn nguyn tc caphn ng ny bng cch thm thuc th Folin-Ciocalteau lm tng nhy ca phn ng sau khi thc hin phn ng biure, ng thi da vocc gc Tyr, Try nhthuc th to phc mu xanh da tri.

O- O-

C =NH HN = C

HN O Cu O NH

C C

NH HN

Hnh 3.15. Phc mu tm trong phn ng Biure

C mt s phng php tch phn lp v xc nh thnh phn, slng v trnh t amino acid trong peptide.

V nguyn tc chung cc phng php tch phn lp v xc nhpeptide v cbn cng nhi vi protein. Tuy nhin peptide l nhngon ngn ca chui polypeptide, v th c th b qua giai on ct chui polypeptide thnh cc peptide nh m c th tch, phn l p ngay bngphng php in di hay sc k tch ring tng peptide.

Sau khi tch ring cc peptide, tin hnh thu phn hon tonthnh cc amio acid t do, xc nh cc amino acid , amino acid u N-tncng v amino acid u C-tn cng. Cc d liu thu c qua s phn tchny sc so snh i chiu v tng hp li.

V d, Puppy v Bodo phn tch mt peptide ca dch khi thuphn Cytocrom C thu c cc d kin sau y:

- Thnh phn amino acid ca peptide sau khi c thu phn honton v tin hnh sc k l 2Cys, 1 Ala, 2 Glu, 1His, 1Thr, 1Val,v 1Lys.




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- Dng phng php Sanger xc nh c amino acid u N-tncng l Cys v phng php carboxypeptidase xc nh c amino acid

u C - tn cng l Lys.- Cu to ca peptide nh (bng cch thu phn tng phn ban uv xc nh cc amino acid, amino acid u N - tn cng v amino acidu C - tn cng ca mi peptide nh):

Cys- Ala Glu- Cys (Val- Glu)

Cys-(Ala,Glu) Cys- His Thr (Val, Glu)

Ala- Glu Glu (Cys, His) Glu- Lys

Thr (Val, Glu, Lys)

Tng hp cc d kin trn, h xc nh c trnh t cc aminoacid ca peptide nghin cu l:

H N-Cys-Ala-Glu-Cys-His-Thr-Val-Glu-Lys-COOH.2y l nguyn tc chung xc nh mt trnh t trong peptide.

Tuy nhin i vi nhng peptide di, vic xc nh rt phc tp.

3.2.3. Cc peptide thng gp trong thin nhin

Trong t nhin tn ti nhiu dng peptide c chc phn quan trong

lin quan n hot ng sng ca c th nh l cc hormon, cc chtkhng sinh hay nhng cht tin thn ca t bo vi khun v.v... Bn cnh cng c nhng peptide chc phn cha r rng, c nhng peptide lsn phm thu phn ang cn dang d ca protein. Trong phm vi cagio trnh ny xin c gii thiu mt s peptide quan trng,c nhiu ngha i vi cho hot ng sng ca sinh vt.

3.2.3.1. Glutathion v cc cht tng t

Glutathion l mt tripeptide -glutamyl-cysteyl-glycine c cng

thc cu to nh sau: CH SHNH2 2HOOC-CH-CH -CH -CO-NH-CH-CO-NH-CH -COOH2 2 2

Trong cu trc ca glutathion, nhm SH ca cysteine l nhm hotng, v vy ngi ta thng vit tt ch glutathion l G-SH. y lglutathion dng kh. Trong mi trng hot ng glutathion c th




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nhng hydrogen (H) thnh dng oxy ho (GSSG) v ngc li c thnhn H thnh dng kh:

-2H

2GSH G-S-S-G+2H

Nhphn ng trn, glutathion ng vai tr ca mt h thng oxyho kh (vn chuyn hydrogen). Glutathion l mt trong nhng peptideni bo ph bin nht, n phn b nhiu trong cc m v cc cquan nh:gan, thn, lch, tim, phi, hng cu v.v...

3.2.3.2. Cc hormone sinh trng (HGH)Hormone sinh trng ca ngi (HGH-human growth hormone)

cn c tn gi STH (somatotropin hormone) l mt chui polypeptide baogm 191 amino acid c khi lng phn t 20.000. Trong cu trc c haicu disulfua c to thnh gia amino acid 53 -165 v gia amino acid182-189. Hot ng sinh hc ca HGH l chui gm 134 aminoacid. HGH c cu to rt ging vi hormon lactogen ca rau thai(85% amino acid ging nhau) v gn ging prolactin ca ngi (32%

amino acid ging nhau).Hormon sinh trng c tc dng i vi s tng trng ni chung,

kch thch s to sn hn l to xng, n cng l mt hormon chuynho. Hormon sinh trng kch thch s tng hp protein t nhng aminoacid c vn chuyn d dng vo trong t bo nh chng, v lhormon gy tng ng huyt, sinh i tho ng, ng thi kch thchs thoi ho lipid m bo nhu cu v nng lng cho cth, gy tngacid bo t do trong huyt tng.

S thiu ht HGH nu xy ra trc tui dy th s dn n chngngi ln, s d tha HGH nu xy ra trc tui dy th s dn n chngngi khng l, nu xy ra sau tui dy th s dn n chng ngi b tocc (pht trin chiu dy ca u, xng v mt).




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3.2.3.3. InsulinT 1953, Sanger (gii thng

Nobel 1958) nghin cu, tinh chv xc nh hon ton cu trc caphn t insulin. Phn t insulin bao gm51 amino acid, c cu trc gm 2 chuipolypeptide, vi khi lng phn t 5.700chui A c 21 amino acid, chui B c 30amino acid. Hai chui c ni vi nhaubng 2 cu disulfua. Trong chui A cnghnh thnh 1 cu disulfua gia amino acidth 6 v amino acid th 11. Phn c hiu(c trng ca mt loi) ch tp trung vocc amino acid th 8-9-10, 12-14 cachui A v c bit l amino acid th 30ca chui B (hnh 3.16).

Ngi ta cng xc nh ccu trc ba chiu ca insulin v thy rngcu trc phn t insulin c gi vngbi nhiu lin kt mui, lin kt hydrov lin kt cu disulphate gia chui Av chui B.Insulin c tc dng r nht trong tt ccc hormon ca tuyn tu, c bit ivi qu trnh chuyn ho glucid, n ctc dng h ng huyt. Insulin cnkch thch qu trnh tng hp v c chqu trnh thoi ho glycogen c, ganv m m. c bit, insulin tng cngtng h p acid bo, protein v kch

thch s ng phn. Tc dng quantrng nht ca insulin l kch thch sthm nhp glucose, mt s ose, aminoacid trogn t bo c v m. Do vyinsulin lm gim lng glucose trongmu. Ngoi ra insulin cng lm gims tn to glucose do lm gim nng enzyme nh pyruvat carboxylase vfructose 1-6 diphosphatase.

Hnh 3.16. Cc amino acid cachui A v B insulin b




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3.2.3.4. Oxytocin, Vasopressin Vasotocin

Oxytocin l mt peptide c 9 amino acid. ng vt c v,

oxytocin ch khc s thay i ca 2 amino acid l: amino acid v trth ba l isoleucine v amino acid v tr th tm l leucine (bng 3.3).Vasopressin ca loi ch nhi c cu trc trung gian gia vasopresin voxytocin ca ng vt c v (amino acid th ba l isoleucin v amino acidth tm l arginine v c tn l vasotocin). Vasopressin l mt peptide ccu trc gm 9 amino acid. .Bng 3.3. So snh cu trc ho hc gia oxytocin v vasopressin ca mt s

loi ng vt

1 2 3 4 5 6 7 8 9LysineVa- Ln,

Cys-Tyr-Phe-Glu-Asn-Cys-Pro-Lys-Gly-NHVaso- H m2pressin

Phn lnng vt c

v

So-

1 2 3 4 5 6 7 8 9Argininevasopressin Cys-Tyr-Phe-Glu-Asn-Cys-Pro-Arg-Gly-NH2

pres

ng vt cxng sng,

khng c v

1 2 3 4 5 6 7 8 9

Vasotocin Cys-Tyr-Ile-Glu-Asn-Cys-Pro-Arg-Gly-NHsin 2

ng vt cxng sngc v, chim

Oxytocin 1 2 3 4 5 6 7 8 9

Cys-Tyr-Ile-Glu-Asn-Cys-Pro-Leu-Gly-NH2

Phn ln ng vt c v amino acid th 8 ca vasopressin larginine (arg-vasopressin), trln v h m, amino acid th 8 l lysine (lys-vasopressin). Oxytocin c tc dng trn ctrn ca t cung v tuyn v, gy

co khi t cung sinh con v kch thch s tit sa khi cho con b.Vasopressin c tc dng chng li niu, tng cng ti h p thu

nc thn, ng thi lm co mch, do c tc dng tng huyt p.

3.3. Protein

3.3.1. Cu trc phn tbc 1, 2, 3, 4

V mt cu trc ngi ta phn bit protein gm bn bc: bc I, bc II,bc III v bc IV (Hinh. 3.17)




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Bc I Bc II Bc III Bc IV

Hnh 3.17. S cc bc cu trc ca protein

3.3.1.1. Cu trc bc I

Cu trc bc I biu th trnh t cc gc amino acid trong chuipolypeptide, cu trc ny c gi vng bng lin kt peptide (lin kt cngha tr). Cu trc bc I l phin bn ca m di truyn, vic xc nh c cutrc bc I l cs tng hp nhn to protein bng phng php ho hchoc bng k thut ca cng ngh sinh hc.

Hin nay nhiu loi protein bit c trnh t cc amino acid

trong chui polypeptide nh: ribonuclease l mt protein c 124 aminoacid c ni vi nhau thnh mt chui, c 4 cu disulfua (hnh 3.18);hemoglobin l protein c 4 chui polypeptide, 2 chui ( mi chui 141amino acid) v 2 chui (mi chui 146 amino acid); trypsinogen b (229amino acid); kimotrypsin b (229 amino acid); alcol dehydrogenase nga(374 amino acid); glutamate dehydrogenase b (500 amino acid) v.v..




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Hnh 3.18. Cu trc bc nht ca ribonuclesae ca b

3.3.1.2. Cu trc bc II

Biu th s xon ca chui polypeptide, l tng tc khng gian giacc gc amino acid gn nhau trong mch polypeptide.

Xon

Lin kthydrogen

Xon

Hnh 3.19. Cc kiu xun trong cu trc bc II ca protein

Ni cch khc, cu trc bc II l dng khng gian cc b ca tngphn trong mch polypeptide. Cu trc ny c lm bn nhcc lin kt




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hydrogen c to thnh gia lin kt peptide k gn nhau, cch nhaunhng khong xc nh. Theo Pauling v Cori (1951) cu trc bc II caprotein bao gm 2 kiu chnh l xon v phin gp .

trong tc ngi ta tm thy keratin l loi protein c hai dng cutrc: dng bnh thng v dng dui thng.; cu trc phin gp tm thytrong fibroin ca t. Cu trc xun hin nay c tm thy trong nhiu loiprotein khc nhau Mt khc t l % xon trong cc protein khc nhau cngthay i kh nhiu. V d trong hemoglobin v mioglobin l 75%; lysosyme l35%; ribonuclease l 17% ..

Bng 3.4. S lng xon v phin gp trong chui n mt s proteinS gc (%)

Protein (s gc) Xon Phin gp 4514Chymotrypsin (247)

3526Ribonuclease (124)

1738Carboxypeptidase (397)

039Cytochrom C (104)

1240Lysosyme (129)

078Myoglobin (153)

Ngoi ra cn c kiu xon collagen c tm thy trong phn tcollagen (hnh 3.20).

Hnh 3.20. Cu trc kiu xun collagen




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n v cu trc ca n l tropocollagen bao gm 3 mchpolypeptide bn vo nhau thnh mt dy cp siu xon (v mi mch nc cu trc xon, chiu cao ca mi gc xon trn trc siu xon ny l2,9 anstron, mt vng xon l 3,3 gc amino acid. Ba chui polypeptidetrong dy cp ni vi nhau bng cc lin kt hydrogen.

3.3.1.3. Cu trc bc III

Biu th s xon v cun khc ca chui polypeptide thnh khi,c trng cho potein cu, l tng tc khng gian gia cc gc amino acidxa nhau trong chui polypeptide. Trong nhiu protein hnh cu c chacc gc Cys to nn lin kt disulfua gia cc gc Cys xa nhau trongchui polypeptide lm cho chui b cun li (xem myoglobin hnh 3.21).

Ngoi ra cu trc bc III cn c gi vng bng cc loi lin kt khcnh Van der Waals, lin kt hydrogen, lin kt tnh in gia cc gcamino acid v.v...

3.3.1.4. Cu trc bc IV

Biu th s kt hp ca cc chui c cu trc bc III trong phn t protein. Hay ni cch khc, nhng phn t protein c cu trc t 2 haynhiu chui protein hnh cu, tng tc vi nhau trong khng gian to nncu trc bc IV. Mi mt chui polypeptide c gi l mt tiu n v

(subunit), chng gn vi nhau nhcc lin kt hydrogen, tng tc Vander Waals gia cc nhm phn b trn b mt ca cc tiu n v lmbn cu trc bc IV.

Myoglobin Hemoglobin

Hnh 3.21. Cu trc bc III ca myoglobin v bc IV ca hemoglobin

(hemoglobin l protein c 4 chui polypeptide2 chui v 2 chui ;myoglobin ch gm mt chui polypeptide)




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3.3.2. Mt vi tnh cht ca protein

3.3.2.1. Tnh cht l-ho ca protein

- Tnh tan ca proteinCc loi protein khc nhau c kh nng ho tan d dng trong mt

s loi dung mi nht nh, chng hn nh albumin d tan trong nc;globulin d tan trong mui long; prolamin tan trong ethanol, glutelin chtan trong dung dch kim hoc acid long v.v...

- Tnh ngm nc ca protein

Trong mi trng nc, protein kt hp vi nc trng ln trthnh dng keo, hay ni cch khc protein trng thi hydrate ho, ccphn t nc bm vo cc nhm a nc trong phn t protein nh -NH2,

-COOH..., lp o nc bao quanh phn t protein l mt trong cc yu tlm bn vng cu trc, ngn cch cc phn t protein khng cho chngdnh vo nhau thnh ta.

- nht ca dung dch protein

Khi protein ho tan trong dung dch, mi loi dung dch ca nhngprotein khc nhau c nht khc nhau (bng 3.5). Ngi ta c th lidng tnh cht ny xc nh khi lng phn t ca protein ( nhtcng cao th khi lng phn t cng cao).

Bng 3.5. nht ca mt s protein

Nng % nht tng iProtein

(trong nc) (ca nc =1)

4,543,0Gelatin

1,203,0Albumin trng

14,28,0Gelatin

1,578,0Albumin trng

- Hng sin mi ca dung dch protein

Khi thm cc dung mi hu ctrung tnh nh ethanol, aceton vodung dch protein trong nc th tan ca protein gim v protein s ktta do vic gim mc hydrate ho ca cc nhm ion ho ca protein,lp o mt nc, cc phn t protein kt hp vi nhau thnh ta. Nhvy, hng sin mi ca dung mi lm ngn cn lc tnh in giacc nhm tch in ca protein v nc. Mi lin h c ctrng bi biu thc:




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L1 - l2F =

2

DrTrong : D - hng sin mi ca dung dch

F- lc tnh in gia cc ion tch in

L1 , l - in tch cc ion, r - khong cch gia cc ion2- Tnh cht in li ca protein

Cng nh cc amino acid, protein l cht in li lng tnh v trongphn t protein c nhiu nhm phn cc mnh (bn gc R) ca amino acidv d: nhm COOH th hai ca Asp, Glu; nhm NH2 ca Lys; nhm OH

ca Ser, Thr, Tyr v.v...Trng thi tch in ca cc nhm ny ph thucvo pH ca mi trng. mt pH no m tng in tch (+) v intch (-) ca phn t protein bng khng, phn t protein khng di chuyntrong in trng gi l pHi (isoelectric - im ng in) ca protein.Nh vy protein cha nhiu Asp, Glu (amino acid c tnh acid mnh) thpHi trong vng acid, ngc li nhiu amino acid kim nh Lys, Arg, Histh pH trong vng kim.i

mi trng c pH < pHi , protein a s l mt cation, sintch dng ln hn sin tch m. pH > pHi phn t protein th hintnh acid, cho ion H+, do sin tch m ln hn sin tch dng,protein l mt a anion, tch in m.

Bng 3.5. Gi tr pHi ca mt s protein

Protein pH Protein pHi i

5,2Globulin sa1,0Pepsin

6,8Hemoglobin4,6Albumin trng

7,8Ribonuclease4,7Casein

10,5Trypsin4,9Albumin huyt thanh

10,6Cytochrom C4,9Gelatin12,0Prolamin

Trong mi trng c pH = pHi ca protein, protein d dng kt t livi nhau v th ngi ta li dng tnh cht ny xc nh pHi ca proteincng nh kt ta protein. Mt khc do s sai khc nhau v pHi gia ccprotein m c thiu chnh pH ca mi trng tch ring cc protein rakhi hn hp ca chng.




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- S kt ta bng mui ca dung dch protein

Mui trung tnh c nh hng r ti ho tan ca protein hnh cu:

vi nng thp chng lm ho tan nhiu protein. Tc dng khng phthuc vo bn cht ca mui trung tnh, m ph thuc vo nng mui v sin tch ca mi ion trong dung dch, tc l ph thuc vo lc ion ca dungdch ( = 1/2 C1 Z1,

2 trong l k hiu ca tng, C1 l nng ca miion, Z1 l in tch ca mi ion). Cc mui c ion ho tr 2 (MgCl2, MgSO4...)lm tng ng k tan ca protein hn cc mui c ion ho tr 1 (NaCl, NH4Cl,KCl...). Khi tng ng k nng mui trung tnh th tan ca protein bt ugim vnngmui rt cao, protein c th b kt ta hon ton.

Cc protein khc nhau b kt ta nhng nng mui trung tnh

khc nhau. Ngi ta s dng tnh cht ny chit xut v tch ring proteinkhi hn hp. l phng php dim tch (kt ta protein bng mui). Thd dng mui amonium sulfate 50% bo ho kt ta globulin v dung dchamonium sulfate bo ho kt ta albumin t huyt thanh.

- Biu hin quang hc ca protein

Cng nh nhiu cht ho hc khc, protein c kh nng hp th vbc x nh sng di dng lng t h. V vy c tho cng hp thca protein trong dung dch hay cn gi l mt quang thng k hiu bngch OD (Optical Density). Da trn tnh cht ngi ta sn xut ra cc

loi my quang ph hp th phn tch protein. Nhn chung protein u ckh nng hp th nh sng trong vng kh kin (t 350nm- 800nm) v vngt ngoi (t 320nm xung ti 180nm).

Trong vng nh sng kh kin protein kt hp vi thuc th hp thmnh nht vng nh sng 750nm (nh lng protein theo Lowry).

i vi vng t ngoi dung dch protein c kh nng hp th nh sngt ngoi hai vng bc sng khc nhau: 180nm-220nm v 250nm - 300nm.

bc sng t 180nm-220nm l vng hp th ca lin kt peptidetrong protein, cc i hp th190nm. Do lin kt peptide c nhiu trong

phn t protein nn hp th kh cao, cho php nh lng tt c cc loiprotein vi nng thp. Tuy nhin vng hp th ny ca cc lin kt peptidetrong protein c th b dch v pha c bc sng di hn khi c mt s tpcht ln trong dung dch protein. Mt khc chnh cc tp cht ny cng hp thnh sng t ngoi vng bc sng 180nm-220nm. V th trong thc tthng o hp th ca dung dch protein bc sng 220nm-240nm.

bc sng t 250nm-300nm l vng hp th cc amino acid thm(Phe, Tyr, Trp) c trongphn t protein hp th cc i 280nm. C th sdng phng php o hp th ca dung dch protein bc sng 280nm




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nh tnh v nh lng cc protein c cha cc amino acid thm. Hmlng cc amino acid thm trong cc protein khc nhau thay i kh nhiu, do dung dch ca cc protein khc nhau c nng ging nhau c th khcnhau v hp thbc sng 280nm. Ngoi ra c nhiu cht khc trongdung dch cng c nh hng n h p th protein. V vy, cc phngphp o hp thvng nh sng t ngoi thng c dung nh lngprotein c tinh sch hoc xc nh protein trong cc phn on nhnc khi sc k tch cc protein qua ct.

- Kt ta thun nghch v khng thun nghch protein

Khi protein b kt ta n thun bng dung dch mui trung tnh cnng khc nhau hoc bng alcohol, acetone nhit thp th protein vngi nguyn c mi tnh cht ca n k c tnh cht sinh hc v c th hotan trli gi l kt ta thun nghch. Cc yu t kt ta thun nghch cdng thu nhn ch phm protein. Trong qu trnh kt ta thun nghch muitrung tnh va lm trung ho in va loi b lp v hydrate ho ca protein,cn dung mi hu cvn ho nc s ph hy lp v hydrate nhanh chng.Trong ch phm protein nhn c cn ln cc cht dng kt ta, cn sdng phng php thch hp loi b cc cht ny. V d c th dngphng php thm tch loi b mui.

Ngc li kt ta khng thun nghch l protein sau khi b kt takhng th phc hi li trng thi ban u. S kt ta ny thng c s dng loi b protein ra khi dung dch, lm ngng phn ng ca enzyme. Mttrong nhng yu t gy kt ta khng thun nghch n gin nht l un sidung dch protein (s ni k hn trong phn bin tnh protein sau).

- Cc phn ng ho hc ca protein

Cng nh cc amino acid v peptide, protein c cc phn ng ho hctng t, l: phn ng ca cc nhm -COOH, -NH2, gc R v phn ng tomu c trng ca lin kt peptide nh phn ng biure (xem chng 2 v 3. y xin c gii thiu thm mt s phn ng mu c trng khc, c nghaquan trng trong pht hin protein v cc gc amio acid trong chuipolypeptide.

+ Phn ng vi thuc th Folin-Ciocateau

Thuc th Folin-Ciocateau c cha phosphomolipdic acid vphosphovolframic acid cc cht ny lm tng nhy ca phn ng biure, mtkhc phn ng vi gc Tyr v Trp trong phn t protein. Cc gc amino acidny tham gia trong qu trnh to phc cht mu xanh da tri.

+ Cc phn ng mu c trng khc ca protein




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Nhng phn ng ny c c l do s c mt ca cc nhm nh chcha hc xc nh trong phn t protein. C th s dng chng pht hinamino acid, protein trong dung dch.

Phn ng xanthproteic: cc gc amino acid Tyr, Trp, Phe trongprotein tc dng vi HNO3c to thnh mu vng v sau khi thm kims chuyn thnh da cam.

Phn ng Pauli: cc gc Tyr, His trong protein tc dng vidiazobenzosulfonic acid to thnh mu anh o.

Phn ng Millon: gc Tyr tc dng vi thu ngn nitrate trongHNO c to thnh kt ta mu nu t.3

Phn ng Saccaguichi: gc Arg tc dng vi dung dch kim ca-naphtolv hypobromitecho mu anh o.

Phn ng Adamkievich: gc Trp tc dng vi glyoxylic acid vH SO c to thnh vng tm mt phn cch.2 43.3.2.2. Tnh cht v chc nng sinh hc ca protein

Protein l hp cht hu cc ngha quan trng bc nht trong cth sng, v mt s lng, n chim khng di 50% trng lng kh cat bo. T lu, bit rng protein tham gia mi hot ng sng trong cth sinh vt, ngoi vai tr l thnh phn chnh trong cu trc ca t bo v

m, protein cn c nhiu chc nng phong ph khc quyt nh nhng cim cbn ca s sng nh s truyn t thng tin di truyn, s chuynho cc cht do cc enzyme, cc khng th chng li bnh tt, cc hormondn truyn cc tn hiu trong t bo v.v... u c bn cht l cc protein.Trong cth protein c mt s vai tr sau y:

- Chc nng to hnh

Ngoi cc protein lm nhim v cu trc nh v virus, mng tbo, cn gp nhng protein thng c dng si nh: sclerotin c trong lpv ngoi ca su b; fibroin ca t tm, nhn; collagen, elastin ca m

lin kt, m xng. Collagen m bo cho bn v tnh mm do cam lin kt.

- Chc nng xc tc

Hu ht cc phn ng xy ra trong c thu do cc protein cbit ng vai tr xc tc, nhng protein c gi l cc enzyme. Mcd gn y ngi ta pht hin c mt loi RNA c kh nng xc tcqu trnh chuyn ho tin RNA thng tin (pre-mRNA) thnh RNA thngtin (mRNA), ngha l enzyme khng nht thit phi l protein. Nhng nhngha c tnh cht kinh in: enzyme l nhng protein c kh nng xc tc




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c hiu cho cc phn ng ho hc, l cht xc tc sinh hc vn c nghac bit quan trng. Hin nay ngi ta bit c khong 3.500 enzyme khcnhau, nhiu enzyme c tinh sch, kt tinh v nghin cu cu trc.

- Chc nng bo v

Ngoi vai tr l thnh phn chnh trong xc tc, cu trc ca t bov m, protein cn c chc nng chng li bnh tt bo v cth. lcc protein tham gia vo h thng min dch, c bit nhiu loi proteinthc hin cc chc nng ring bit to nn hiu qu min dch c hiu vkhng c hiu. Cc protein min dch c nhc n nhiu hn c l cckhng th, b th v cc cytokine.

Ngoi ra protein cn tham gia vo qu trnh ng mu chng

mt mu cho c th hoc mt s loi c th sn xut ra nhng c t cbn cht l protein nh enzyme nc rn, lectin v.v...,c kh nng tiu ditk th bo v cth.

- Chc nng vn chuyn

Trong c th c nhng protein lm nhim v vn chuyn nhhemoglobin, mioglobin, hemocyanin vn chuyn O2, CO v H

+2 i khp

cc m, cc cquan trong cth. Ngoi ra cn c nhiu protein khc nhlipoprotein vn chuyn lipid, ceruloplasmin vn chuyn ng (Cu) trongmu v.v...Mt trong nhng protein lm nhim v vn chuyn c nhc

n nhiu nht l hemoglobin.- Chc nng vn ng.

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

-Chc nng d tr v dinh dng

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

- Chc nng dn truyn tn hiu thn kinhNhiu loi protein tham gia vo vic dn truyn tn hiu thn kinh ivi cc kch thch c hiu nh: sc t th gic rodopsin mng li mt.

- Chc nng iu ho

Cc protein lm nhim viu ho qu trnh trao i cht thngqua tc ng ln b my thng tin di truyn nh cc hormon, cc proteinc chc hiu enzyme u c chc nng iu ho nhiu qu trnh traoi cht, chng hn cc protein repressorvi khun c th lm ngng qutrnh sinh tng hp enzyme t cc gen tng ng.




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- Chc nng cung cp nng lng

Protein cng l ngun cung cp nng lng quan trng cho mi

hot ng sng trong c th. Trong c th cc protein b phn gii thnhcc amino acid, t tip tc to thnh hng lot cc sn phm, trong c cc ceto acid, aldehyde v carboxylic acid. Cc cht ny u b oxy hodn dn to thnh CO v H O ng thi gii phng ra nng lng.2 23.3.3. Phn loi protein

Protein l h p cht a dng v thnh phn cu trc, chc nng;khi lng phn t ca chng cng rt khc nhau (bng 3.6). Do sphn loi protein c th da vo nhng mc ch khc nhau. C hai cchphn loi thng thng nht:

3.3.3.1. Phn loi theo hnh dng- Protein dng si

C hnh dng di, thng l hnh si, chiu di ca phn t proteinsi ln hn ng knh ca n hng trm ln. Protein si tng i bnvng, khng tan trong nc v dung dch mui long, cc chui polypeptide ca protein si nm dc theo mt trc thnh nhng si di.Protein si l yu t cu trc cbn ca m lin kt ng vt cao cp,th d collagen gn v m xng,elastin m lin kt n hi, -keratintc da v.v...

- Protein dng cuC dng gn nh hnh cu hoc hinh bu dc, chiu di ca phn t

protein cu c th ln hn ung knh ca n t 3 n 10 ln. Protein cu khngbn vng bng protein si, a s tan trong dung dch nc v d khuych tn,thng c chc nng hot ng sng ca t bo nh cc enzyme, cc hormon, ccprotein vn chuyn nh albumin huyt thanh, hemoglobin v.v...

- Protein dng trung gian

Mt s protein dng trung gian, va c c im ca protein si,

va c c im ca protein cu. Th d myosin (yu t cu trc v chcnng quan trong ca c) c cu trc hnh que di l c im ca proteinsi, nhng li tan trong dung dch mui l c im ca protein cu. Ngoi ra, trong nhm trung gian ny cn c cht tin thn ca fibrin lfibrinogen.

3.3.3.2. Phn loi theo thnh phn ho hc

Protein gm hng trm, hng ngn, thm ch hng vn amino acidni vi nhau bng lin kt peptide to nn mt hay nhiu chuipolypeptide c cu trc rt phc tp.




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Cn c s c hay vng mt ca mt s thnh phn c bn chtkhng phi protein m ngi ta chia protein thnh hai nhm:

Bng: 3.6 Khi lng (MW) v cu trc phn tca mt s protein

Protein Khi lng(Dalton)

S gcamino acid

S chuipolypeptide

1293482Glucagon

2515733Insulin

112412.640Ribonuclease (ty b)

112913.930Lysozyme (lng trng trng)

115316.890Myoglobin (tim nga)

324122.600Chymotripsin (ty b) 457464.500Hemoglobin (ngi)

155068.500Albumin (huyt thanh ngi)

480096.000Hexokinase (men bia)

4975117.000Tryptophan-synthetase (E.coli)

41.250149.000-globulin (nga)44.100495.000Glycogen-phosphorylase (cth)408.3001.000.000Glutamate-dehydrogenase (gan b)2120.0002.300.000Synthetase ca acid bo (men bia)

2.130336.50040.000.000Virus khm thuc l

- Protein n gin

Protein n gin l nhng protein m phn t ca chng gm tonamino acid. Th d mt s enzyme ca tu b nh ribonuclease gm

ton amino acid ni vi nhau thnh mt chui polypeptide duy nht(c 124 gc amino acid, khi lng phn t 12.640), chymotrypsin gm tonamino acid ni vi nhau thnh ba chui polypeptide (c 241 gc amino acid,khi lng phn t 22.600) v.v...Da theo kh nng ho tan trong nc hoc

trong dung dch ngi ta c th chia cc protein n gin ra mt s nhm nhnh:

- Albumin: tan trong nc, b kt ta nng mui (NH4)2SO4 khcao (70-100%).

- Globulin: khng tan hoc tan t trong nc, tan trong dung dch longca mt s mui trung tnh nh NaCl, KCl, Na2SO4..., v b kt ta nng mui (NH4)2SO4 bn bo ho.

- Prolamin: khng tan trong nc hoc dung dch mui long, tantrong ethanol, isopropanol 70-80%.




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- Glutein: ch tan trong dung dch kim hoc acid long.

- Histon: l protein c tnh kim d tan trong nc, khng tan trong

dung dch amoniac long.- Protein phc tp

Protein phc tp l nhng protein m phn t ca chng ngoi ccamino acid nh protein n gin cn c thm thnh phn khc c bn chtkhng phi l protein cn gi l nhm thm (nhm ngoi). Tu thuc vobn cht ca nhm ngoi m ngi ta chia cc protein phc t p ra ccnhm nh v thng gi tn cc protein bt u bng tip u ng chbn cht nhm ngoi:

- Lipoprotein: nhm ngoi l lipid.

- Nucleoprotein: nhm ngoi l nucleic acid.- Glucoprotein: nhm ngoi l carbohydrate v dn xut ca n.

- Phosphoprotein: nhm ngoi l phosphoric acid.

- Chromoprotein: nhm ngoi l h p cht c mu. Tu theo tnhcht ca tng nhm ngoi m c nhng mu sc khc nhau nh (hemoglobin), vng (flavoprotein)...




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TI LIU THAM KHOTi liu ting Vit

1. Trn Th n, i Duy Ban, Nguyn Hu Chn, nh H, L cTrnh. 1980. Ho sinh hc. NXB Y hc, H Ni

2.Phm Th Trn Chu, Trn Th ng. 1999. Ho sinh hc. NXB Giodc, H Ni.

3. Nguyn Ln Dng, Phm Vn Ty, Nguyn nh Quyn. 1999. Vi sinhvt hc. NXB Gio dc,H Ni.

4. L c Trnh. 1998. Hormon. NXB Y hc. H ni

Ti liu ting Anh

1. Dennison C. 2002. A Guide To Protein Isolation. Kluwer AcademicPublishers. New York, Boston, Dordrecht, Lodon, Moscow.

2. Fersht A., 1998, Structure and Mechanism in Protein Science, W. H.Freeman, 3rd Rev Edit.

th3. Lehninger A. L. 2004. Principle of Biochemistry, 4 Edition. W.HFreeman, 2004

4. Liebler D. C. 2002. Introduction to proteomics. Humana Press Inc.Totuwa, New Jersey.

5. Lodish H, 2003. Molecular Cell Biology. 5th ed, W.H Freeman, 2003

6. Walker J. M. 1996. The Protein Protocols Hand book. 2nd ed. HumanaPress Inc. Totuwa, New Jersey.




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Chng 4

Nucleic acid

4.1. Thnh phn ho hc ca nucleic acid Nucleic acid, vt cht mang thng tin di truyn ca cc h thng

sng, l mt polymer c hnh thnh t cc monomer l nucleotide.Trong nucleic acid c cha cc nguyn t C, H, O, N v P. Hm lng Pt 8- 10% Mi nucleotide gm 3 thnh phn kt hp vi nhau theo t l1:1:1, bao gm: nhm phosphate, ng pentose (l ng 5 carbon) vmt base nit(nitrogen).

4.1.1 Base nit(Nitrogen)

Cc base nit(nitrogen) thuc phn t nucleic acid u l dn xutca base purine hoc pyrimidine. Cc base purine gm adenine (6-amino purine) v guanine (2-amino, 6-aminopurine), cc base nit pyrimidinegm thymine (2,6-dioxy, 5-methylpyrimidine), cytosine(2-oxy,6-aminopyrimidine) v uracil (2,6 dioxypyrimidine).( Hnh 4.1.)

Hnh 4.1 Cng thc cu to ca cc base nit(nitrogen) trong nucleic acid

4.1.2ng pentose

ng pentose trong nucleic acid gm c hai loi l ng deoxyribosev ribose. S c mt ca 2 loi ng ny l mt trong nhng c im phnbit DNA v RNA.

4.1.3 Phosphoric acid

L mt acid v c- H3PO4




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Hnh 4. 2. Cng thc cu to ca hai loi ng pentose trong nucleic acid

4.1.4. Sto thnh nucleoside

Nucleoside l sn phm thu phn khng hon ton ca nucleicacid. Nucleoside gm c hai thnh phn l ng pentose v mt base nit

(nitrogen, thuc purine hay pyrimidine)

giao trinh hoa sinh_up

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