2

2.4 Proeins

Essenal idea: Proeins hae a ery wide range o! !"ncons in liing organisms.

#ne o! he cenral ideas in Biology is ha sr"c"re dicaes !"ncon. $boe yo" can see ins"lin in is secondary% erary and &"aernary sr"c"res. Polypepdes ary h"gely in he combinaon and n"mber o! amino acids ha hey are composed !rom. Een i! we consider a single polypepde i's properes% and hence i's !"ncon% wo"ld ary grealy depending on i's leel o! sr"c"re. (ns"lin can e)is in all hese !orms% b" he ace !orm% which conrols blood gl"cose leels% is a he erary sr"c"re.

htp://www.bioopics.co."k/as/ins"linproeinsr"c"re.hml

By Chris Paine htps://bioknowledgy.weebly.com/

*ndersandings% $pplicaons and +kills Statement

2.4.U1 2.4.U1 2.4.U2 2.4.U2

2.4.U" 2.4.U"

2.4.U4 2.4.U4 2.4.U% 2.4.U% 2.4.U& 2.4.U& 2.4.U( 2.4.U( 2.4.U* 2.4.U* 2.4.A1 2.4.A1

2.4.A2 2.4.A2 2.4.S1 2.4.S1

Guidance

Amino Amino acids acids are are linked linked toge togethe therr by conde condensa nsatio tion n to form polypeptides. There There are 20 20 differ different ent amin amino o acids acids in polyp polypept eptide ides s Students should kno that most organisms synthesized on ribosomes. use the same 20 amino acids in the same genetic code although there are some e!ceptions. Specific e!amples could be used for illustration. Amino Amino acids acids can can be be linke linked d toget together her in any any se#uence gi$ing a huge range of possible polypeptides. The amino amino acid acid se#ue se#uence nce of of polype polypepti ptides des is is coded coded for by genes. A protei protein n may may consis consistt of a singl single e polype polypepti ptide de or or more than one polypeptide linked together. The amino amino acid acid se#uen se#uence ce determ determine ines s the three' three' dimensional conformation of a protein. )i$ing )i$ing organi organisms sms synt synthes hesize ize many many dif differ ferent ent proteins ith a ide range of functions. +$ery +$ery indi indi$id $idual ual has a uni# uni#ue ue proteo proteome. me. ,ubisc ,ubiscoo- insuli insulinn- immun immunogl oglobu obulin linss- rhodop rhodopsin sin-The detailed structure of the si! proteins collagen and spider silk as e!amples of the range selected to illustrate the functions of proteins of protein functions. is not needed. enatu enaturat ration ion of prote proteins ins by by heat heat or by de$i de$iati ation on of +gg hite or albumin solutions can be used in p/ from the optimum. denaturation e!periments. rain raing g molec molecula ularr diagra diagrams ms to sho sho the form formati ation on of a peptide bond.

2.1.U% Anabolism is the synthesis of comple! molecules from simpler molecules including the formation of macromolecules from monomers by condensation reactions.

Example of anabolism by condensaton

$ ribosome condenses wo amino acids ino a dipepde !orming a pepde bond

-he bonds !ormed are ypes o! coalen bonds.

Bonding monomers ogeher creaes a polymer (mono = one, poly = many)

This is also key to understanding  2.4.U1 Amino Amino acids are linked together by condensation to form polypeptides.  2.4.S1 raing molecular diagrams to sho the formation of a peptide bond.

2.4.U2 There are 20 different amino acids in polypeptides synthesized on ribosomes.

0ibosomes are he molec"les wihin cells ha !aciliae he !ormaon o! pepde bonds and bonds  and hence where polypepdes are synhesi1ed

pepde bond

htps://en.wikipedia.org/wiki/,ile:Pepdesyn.png

2.4.U2 There are 20 different amino acids in polypeptides synthesized on ribosomes.

n.b. here are 22 amino acids% b" only 2 amino acids are encoded by he "niersal genec code.

2.4.U2 There are 20 different amino acids in polypeptides synthesized on ribosomes.

Hydroxyproline is an e)ample o! an amino acid creaed no by he genec code% b" modi3caon% aer polypepde !ormaon% o! proline 5by he en1yme prolyl hydro)ylase6.



-his modi3caon o! proline increases he sabiliy o! he collagen riple heli).



Collagen is a a sr"c"ral proein "sed o proide ensile srengh in endons% ligamens% skin and blood essel walls.

   e    s    a     l    y    )    o    r     d    y     h     l    y     l    o    r    p

2.4.U2 There are 20 different amino acids in polypeptides synthesized on ribosomes.

“ OMG  OMG  I  I HAVE TO LEARN THE NAMES OF ALL 20 !?!? 

“Rela, no yo" #on$%  , yo" &"'% nee# an aaene'' o* %+e onep%' a' o"%l-ne#. 

2.4.U" Amino acids can be linked together in any se#uence gi$ing a huge range of possible polypeptides.

2.4.U" Amino acids can be linked together in any se#uence gi$ing a huge range of possible polypeptides.

2.4.U" Amino acids can be linked together in any se#uence gi$ing a huge range of possible polypeptides.

(! a polypepde conains "s = amino acids here can be 2 = > ?%28%% possible polypepdes generaed.

@ien ha polypepdes can conain "p o % amino acids 5e.g. -in6 he diAeren possible combinaons o! polypepdes are eAecely in3nie.

2.4.U4 The amino acid se#uence of polypeptides is coded for by genes.

pepde bond

0ibosomes are he sie o! polypepde synhesis% b" ribosomes need a emplae  he messenger 0$% which% in "rn% is ranslaed ranslaed by rans!er 0$ molec"les which% in "rn% carry speci3c amino acids.

D  here does he messenger 0$ come !romF

2.4.U4 The amino acid se#uence of polypeptides is coded for by genes.

2.4.U& The amino acid se#uence determines the three'dimensional conformation of a protein.

(.".U( The se#uence and number of amino acids in the polypeptide is the primary structure. A (.".U* The secondary structure is the formation of alpha helices and beta pleated sheets stabilized by hydrogen bonding. A (.".U3 The tertiary structure is the further folding of the polypeptide stabilized by interactions beteen , groups. A (.".U10 The #uaternary #uaternary structure e!ists in proteins ith more than one polypeptide chain.

-here are !o"r leels o! proein sr"c"re. hich leel a proein con!orms o is deermined deermined by iGs amino acid se&"ence.

5Polypepde6  -he order / se&"ence o! he amino acids o! which he proein is composed  ,ormed by coalen pepde bonds beween adacen amino acids  Conrols all s"bse&"en leels o! sr"c"re

 -he chains o! amino acids !old or "rn "pon hemseles  Held ogeher by hydrogen bonds beween 5nonIadacen6 amine 5IH6 and carbo)ylic 5CI#6 gro"ps  HIbonds proide a leel o! sr"c"ral sabiliy  Fibrous proeins

n./. al%+o"+ yo" #on$% nee# %o /e a/le %o o"%l-ne %+e #-1een% leel' o* '%"%"e *o 3no-n o* %+em +elp' %o "n#e'%an# %+e #-1eene /e%een lo/"la an# 4/o"' po%e-n'. T+-' -' %+o"+ e5"-e# 3nole#e *o AHL (6.7.86 %o 6.7.890)

 -he polypepde !olds and coils o !orm a comple) J shape  Ca"sed by ineracons beween 0 gro"ps 5HI bonds% dis"lphide bridges% ionic bonds and hydrophilic hydrophilic / hydrophobic hydrophobic ineracons6  -erary sr"c"re may be imporan !or he !"ncon 5e.g. speci3ciy o! ace sie in en1ymes6  Globular proeins

 -he ineracon beween m"lple polypepdes or proshec gro"ps  $ proshec gro"p is an inorganic compo"nd inoled in a proein 5e.g. he heme gro"p in haemoglobin6  Fibrous and Globular proeins

2.4.U& The amino acid se#uence determines the three'dimensional conformation of a protein.

Proeins are commonly commonly described as eiher being 3bro"s 3 bro"s or glob"lar in na"re. ,ibro"s proeins hae sr"c"ral roles whereas glob"lar proeins are !"nconal 5ace in a cellGs meabolism6.

(n glob"lar proeins he hydrophobic 0 gro"ps are !olded ino he core o! he molec"le% away !rom he s"rro"nding waer molec"les% his makes hem sol"ble. (n 3bro"s proeins he hydrophobic 0 gro"ps are e)posed and here!ore here!ore he molec"le is insol"ble.

2.4.U( )i$ing organisms synthesize many different proteins ith a ide range of functions.

ohing can compare wih he ersaliy o! proeins. -heir !"nconaliy and "sage in organisms is "nrialled. Functon

Descripton -here are ho"sands o! diAeren en1ymes o caalyse speci3c Caalysis chemical reacons wihin he cell or o"side i. $cn and myosin ogeher ogeher ca"se he m"scle conracons "sed in K"scle conracon conracon locomoon and ranspor aro"nd he body. -"b"lin is he s"b"ni o! micro"b"les ha gie animals cells Cyoskeleons heir shape and p"ll on chromosomes d"ring miosis. -ensile ,ibro"s proeins proeins gie ensile srengh needed in skin% endons% srenghening ligamens and blood essel walls. Plasma proeins ac as cloLng !acors !acors ha ca"se blood o "rn Blood cloLng !rom a li&"id o a gel in wo"nds. -ranspor o! Proeins in blood help ranspor o)ygen% carbon dio)ide% iron and n"riens and gases lipids.

M M

Key examples

0"bisco

collagen

Ney e)amples are o"lined in more deail. $lho"gh a key e)ample spider silk is no menoned aboe as he able re!ers o "ses wihin he organism

2.4.U( )i$ing organisms synthesize many different proteins ith a ide range of functions. Functon

Cell adhesion Kembrane ranspor Hormones 0ecepors Packing o! J$ (mm"niy

Descripton Kembrane proeins proeins ca"se adacen animal cells o sck o each oher wihin ss"es. Kembrane proeins are "sed !or !aciliaed diA"sion and ace ranspor% and also !or elecron ranspor d"ring cell respiraon and phoosynhesis. +ome s"ch as ins"lin% ,+H and OH are proeins% proeins% b" hormones are chemically ery dierse. Binding sies in membranes and cyoplasm !or hormones% ne"roransmiters% ases and smells% and also recepors !or ligh in he eye and in plans. Hisones are associaed wih J$ in e"karyoes and help chromosomes o condense d"ring miosis. -his is he mos dierse gro"p o! proeins% as cells can make h"ge n"mbers o! diAeren anbodies.

Key examples

(ns"lin rhodopsin

imm"noglob"lins

Bioechnologically has allowed "s o "se proeins in ind"sry e)amples are:  en1ymes !or remoing sains in clohing deergen deergen  monoclonal anbodies !or pregnancy ess  ins"lin !or reang diabecs  Jisease reamens reamens @enecally modi3ed organisms are oen "sed as o prod"ce proeins. -his howeer is sll a echnically dic"l and e)pensie process.

2.4.A1 ,ubisco- insulin- immunoglobulins- rhodopsin- collagen and spider silk as e!amples of the range of protein functions.

0"bisco

  



,"ll name rib"lose bisphosphae carbo)ylase En1yme I caalyses he reacon ha 3)es carbon dio)ide !rom he amosphere Proides he so"rce o! carbon !rom which all carbon compo"nds% re&"ired by liing organisms% are prod"ced. ,o"nd in high concenraons concenraons in leaes and algal cells

htp://"pload.wikimedia.org/wikipedia/commons/b/b/KinIleaesI2=.pg

2.4.A1 ,ubisco- insulin- immunoglobulins- rhodopsin- collagen and spider silk as e!amples of the range of protein functions.

(ns"lin



 

$ hormone  signals many cells 5e.g. lier cells6 o absorb gl"cose and help red"ce he gl"cose gl "cose concenraon o! he blood. $Aeced cells hae recepor 5proeins6 on heir s"r!ace o which ins"lin can 5reersibly6 5reersibly6 bind o. +ecreed +ecreed by Q cells in he pancreas and ranspored ranspored by he blood.

-he pancreas o! ype ( diabecs donG prod"ce s"cien ins"lin here!ore hey m"s periodically inec synhecally prod"ced ins"lin o correc heir blood s"gar concenraon. htps://en.wikipedia.org/wiki/,ile:(n1"l7C7$Jn.pg

2.4.A1 ,ubisco- insulin- immunoglobulins- rhodopsin- collagen and spider silk as e!amples of the range of protein functions.

immunoglobulins

   

$lso known as anbodies. -wo angen 5a molec"le on he pahogen which prookes an imm"ne response6 binding sies I one on each RarmG Binding sies ary grealy beween imm"noglob"lins 5hyperariable6 5hyperariable6 o enable hem o respond a h"ge range o! pahogens. #her pars o! he imm"noglob"lin molec"le ca"se a response% e.g. acng as a marker o phagocyes phagocyes 5which eng"l! he pahogen6

2.4.A1 ,ubisco- insulin- immunoglobulins- rhodopsin- collagen and spider silk as e!amples of the range of protein functions.

rhodopsin

    

$ pigmen ha absorbs ligh Kembrane proein proein o! rod cells o! he rena 5ligh sensie region a he back o! he eye6 0hodopsin consiss o! he opsin polypepde s"rro"nding a renal proshec gro"p renal molec"le absorbs a single phoon o! ligh li gh IS changes shape IS change o he opsin IS he rod cell sends a nere imp"lse o he brain Een ery low ligh inensies can be deeced.

2.4.A1 ,ubisco- insulin- immunoglobulins- rhodopsin- collagen and spider silk as e!amples of the range of protein functions.

collagen      

$ n"mber o! diAeren !orms $ll are ropeIlike proeins made o! hree polypepdes wo"nd ogeher. $bo" a &"arer o! all proein in he h"man body is collagen ,orms a mesh o! 3bres in skin and in blood essel walls ha resiss earing. @ies srengh o endons% ligamens% skin and blood essel walls. ,orms par o! eeh and bones% helps o preen cracks and !rac"res o bones and eeh

htps://en.wikipedia.org/wiki/-ooh5h"man6Tmediaiewer/,ile:-eehbyJaid+hankbone.pg

2.4.A1 ,ubisco- insulin- immunoglobulins- rhodopsin- collagen and spider silk as e!amples of the range of protein functions.

spider silk

    

JiAeren ypes o! silk wih diAeren !"ncons Jragline silk is sronger sronger han seel and o"gher han Nelar hen 3rs made i conains regions where he polypepde !orms parallel arrays 5botom6 +ome regions seem like a disordered angle 5middle6 hen he sreched he polypepde grad"ally e)ends% making he silk e)ensible and ery resisan o breaking.

htps://en.wikipedia.org/wiki/+pidersilkTmediaiewer/,ile:$rane"sdiadema"s"nderside?.pg

2.4.U* +$ery indi$idual has a uni#ue proteome.

Genome: all o! he genes o! a cell% a ss"e or an organism T+e enome #e%em-ne' +a% po%e-n' an oan-'m an  po''-/ly po#"e. A enome -' "n-5"e %o mo'% -n#--#"al' (-#en:al %-n' an# lone' '+ae a enome)

Enironmenal !acors T+e en-onmen% -n