Summary
Proteins Summary
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This summary was prepared based on the GCE A level Biology Syllabus
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amino acidsHaemoglobin (globular) : found in ved blood cell , transport O2 , PH
Formationof peptidebudipimaysvuureBraun
buffer
" i
.
44
O
I .. porphyrin ring
H N 2 OH ↑ & Felt
c
addition of 1420
-
group/per naemoglobin
- -
-
P 1AA and the amino
group of another Ad to each subunit I naem , thaem
group
aminoacarby
,
is form covalent peptide boud viatue molecule
·
a
of 1 water molecule
removal Globular
shape -> compact allows many naemoglobin molecules to be
,
↳
·
,
peptide bonds synthesised by ribosomes during translation packed in RBC
.
I non-polar R group hydrophobic
, , insoluble
cataly
pepay transferase
:
non-polar AA narquaternary structure 4 subunits -> haemoglobin mol can
carry 4 O2
a
·
,
4 O/N/S soluble carrier
neutral :
Polar group , ,
hydrophilic , molecules ·
↑ capacity for transport of Oz, naemoglobin efficient or
.
structure :
S polar AA secondary
hydrophilic a
↓
Regroupwith
cooH-acidic ,
7) acidic At folding of polypeptidechain EachsubunitnahempcontainingFerdporphyn ringe
Fertida
:
and
coiling
·
·
hydrophilic e e
groupwithWL-
bavic
metanoperator Fertcominas
, ,
(t) basic At / beta-pleated sweet
alpha-helix of or a
reversibly to O2
: into allows release
.
,
· maintained by hydrogen bonds .
properties of not involved !
group orientated such that Felt is complexed to an amino acid residue
AA :
R group ·
Haem
why ?
leaving other face accessible to bind 02 -> enable O r transport
~
on I face ,
.
insoluble in organic solvents & -helix stabilised bonds
solubility soluble intio
by hydrogen
:
↓
->
·
,
·
Twitterion formation -> In , At existrar
aqueous solution intra-chain H-bonding , 3 .
6 amino did ·
Each subunit has a deep hydrophobic cleft lined with AA with non-polar ,
hydrophobic groups -> provides
binding site for hydrophobic new group
.
conv
having both trea-ve residues in
every turn ,
4 formed by : loss of It from COOK -- ve B pleated : of bonds between , or more ·
tacusubunit folded such that At's with hydrophilic Rgroups are on ext & .
gain of riy by WU2 -> the AA's with hydrophobic R groups in interior -> soluble in aqueous medium ,
part of same polypeptide lying side by , suitable for transport in aqueous cytosol in RBC .
·
buffering capabilities
:
A are amphoteric , ageous solutions of side Canti-paralel/parallel) -4 subunits held together by non-covalent group interactions
->
binding
of O2 to haem group of 1 subunit causes
change
in tertiary structure ,
AA can far buffer solutions which can resist small changes in prl tertiant :
causing tertiary structure of other subunits to change , all subunits
gain increased affinity for O2 -> Cooperative binding for faster loading
could affect globular , 3D conformation of protein formed by
* prevent any sudden
changer in cellular pH that &
unloading of of from haemoglobin molecules
·
·
activity of enrymer and functions of other proteins , further
folding bending of polypeptide chain
maintained b R group interactions , Collagen) fibrous 1 : deposited outside cells structural support forms major , ,
rein forced by
strong disulfide bonds components of bone , Skin etc insoluble , nigh tensile strength no secondary .
,
Bond
stabilising proteins :
& tertiary
·
structure .
hydrogen bondv -> polar R groups in tertiarya quaternary quaternary
: &
primary structure :
repetitive seg- of 3 AA G , X Y Every 3rd At is glycine
·
.
,
, .
(individual weaky multiple strong) disrupted by change in temp & pH) , .
subunits form one functional complex a
lycine hass mallest R group allowing it to fit into centre of triple helix
, ,
protein i held by group interactions enabling fight packing
to form multimeric protein .
ionic bondr acidic basic R
groups in tertiary Quaternary tropocollagen molecule consists of 3 polypeptide chains
:
-
& quaternat · structure
& disrupted by change in
temp & pf)
,
wound around each other to form right handed triple helix ,
Protein denaturation
·
oulfhydry/ groups of cysteine residues intertiary &quaternary unfolding of conformation
disulfide bonds -> 3D within tropolollagen molecule many interchain + bondsbetween
polypeptide
·
~ ,
Istrong covalent broken only under high temp ) backbones resulting in high tensile strength
· H-bonds between
.
, ,
& & temp , -> ↑ thermal agitation -> R group interaction & of 10 from 1AA & H of wrl of another AA ,
disrupted -> lboudr may also be disrupted
hydrophobic interactions -> non-polar R groups intertiary Ranaternary -> - loses
denatured 3D structure ·
Beyond quaternary : N-terminus covalently cross linked to terminus
of hydrophobic
in ag enr polypeptide chain will fold so that max no of
neighbouring tropocollagen
,
, . :
groups come into close contact
interior in shielded from Mo Q changes in
pH -
changes in charges of R
groups mols that
linked tropocollagen
Bundling of many covalently cross
R , ,
hydrophilic &
groups found on exterior ,
a re parallel to each other form collagen fibril -> bundle together
-> alteration of charges onacidic /basic R
groups to form fibre ↑ tensile strength ,
sequence of AA disrupt ionic &H-bonds parauel staggered arrangement of tropocollagen molecules
primarystructure type &
, number ensure
,
:
->
- -
-
along the fibrils ,
-
-
-
I there is no weak spot
unique sequence :
unique shape : function I
metabolic +2 , soluble , - - - -
- - - & -
peptide bonds present protein tightly folded to form spherical shape Irregular AA sea ,
i
lobular
primary structure only n :
. .
quaternary stabilised by H-interactions ionic &H-bonds Tertiary most impt ! ,
.
structural or 144out , insoluble
protein : cross-linked to form long , rope like fibres Regular repetitive AAseg ;
↑ ibrous , I
quaternany stabilised by strny , extensive Hbonds & covalent crosslinks
S
I
secondary most impt !
I
I
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