bsc 2010 ch 8 lecture presents metabolism
TRANSCRIPT
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CAMPBELL
BIOLOGYReece • Urry • Cain • Wasserman • Minorsky • Jackson
© 2014 Pearson Education, Inc.
TENTH
EDITION
CAMPBELL
BIOLOGYReece • Urry • Cain • Wasserman • Minorsky • Jackson
© 2014 Pearson Education, Inc.
TENTH
EDITION
8An Introduction
to Metabolism
Lecture Presentation by
Nicole Tunbridge and
Katleen !it"#atric$
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The Energy of Life
Te li%ing cell is a &iniature ce&ical 'actory(ere tousands o' reactions occur
Te cell e)tracts energy stored in sugars and
oter 'uels and a##lies energy to #er'or& (or$
*o&e organis&s e%en con%ert energy to ligt, as
in biolu&inescence
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!igure 8.1
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!igure 8.1a
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Concept 8.1: An organisms metabolismtransforms matter and energy! sub"ect to thela#s of thermodynamics
Metabolism is te totality o' an organis&+s
ce&ical reactions
etabolis& is an e&ergent #ro#erty o' li'e tat
arises 'ro& orderly interactions bet(een
&olecules
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$rgani%ation of the Chemistry of Life intoMetabolic &ath#ays
- metabolic path#ay begins (it a s#eci'ic&olecule and ends (it a #roduct
Eac ste# is cataly"ed by a s#eci'ic en"y&e
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!igure 8.N01
En%yme 1 En%yme ' En%yme (
)eaction 1 )eaction ' )eaction (&roduct*tarting
molecule
A + C ,
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Catabolic path#ays release energy by brea$ingdo(n cole) &olecules into siler coounds
/ellular res#iration, te brea$do(n o' glucose
in te #resence o' o)ygen, is an e)ale o' a
#at(ay o' catabolis&
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Anabolic path#ays consu&e energy to buildcole) &olecules 'ro& siler ones
Te syntesis o' #rotein 'ro& a&ino acids is an
e)ale o' anabolis&
+ioenergetics is te study o' o( energy 'lo(s
troug li%ing organis&s
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-orms of Energy
Energy is te ca#acity to cause cange Energy e)ists in %arious 'or&s, so&e o' (ic can
#er'or& (or$
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inetic energy is energy associated (it &otion /eat 0thermal energy is $inetic energy associated
(it rando& &o%e&ent o' ato&s
or &olecules
&otential energy is energy tat &atter #ossesses
because o' its location or structure
Chemical energy is #otential energy a%ailable
'or release in a ce&ical reaction
Energy can be con%erted 'ro& one 'or& to anoter
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!igure 8.2
A di2er has more potential
energy on the platform
than in the #ater.
,i2ing con2erts
potential energy to
3inetic energy.
A di2er has less potential
energy in the #ater
than on the platform.
Climbing up con2erts the 3inetic
energy of muscle mo2ement
to potential energy.
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Animation: Energy Concepts
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The La#s of Energy Transformation
Thermodynamics is te study o' energytrans'or&ations
-n isolated syste&, suc as tat a##ro)i&ated by
liuid in a ter&os, is unable to e)cange energy
or &atter (it its surroundings
In an o#en syste&, energy and &atter can
be trans'erred bet(een te syste& and its
surroundings rganis&s are o#en syste&s
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The First Law of Thermodynamics
-ccording to te first la# of thermodynamics,te energy o' te uni%erse is constant
Energy can be transferred and transformed,
but it cannot be created or destroyed
Te 'irst la( is also called te #rinci#le o'
conser%ation o' energy
!i 8
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!igure 8.
0a 0b-irst la# of thermo4
dynamics
*econd la# of thermodynamics
Chemical
energy
/eatC$'
/'$
!igure 8 a
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!igure 8.a
0a -irst la# of thermodynamics
Chemicalenergy
!igure 8 b
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!igure 8.b
0b *econd la# of thermodynamics
/eatC$'
/'$
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The Second Law of Thermodynamics
3uring e%ery energy trans'er or trans'or&ation,so&e energy is unusable, and is o'ten lost
as eat
-ccording to te second la# of thermodynamics
Every energy transfer or transformation increases
the entropy (disorder) of the universe
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Li%ing cells una%oidably con%ert organi"ed'or&s o' energy to eat
*pontaneous processes occur (itout energy
in#ut tey can a##en uic$ly or slo(ly
!or a #rocess to occur (itout energy in#ut,
it &ust increase te entro#y o' te uni%erse
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Biological Order and Disorder
/ells create ordered structures 'ro& less ordered&aterials
rganis&s also re#lace ordered 'or&s o' &atter
and energy (it less ordered 'or&s
Energy 'lo(s into an ecosyste& in te 'or& o' ligt
and e)its in te 'or& o' eat
!igure 8 4
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!igure 8.4
!igure 8 4a
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!igure 8.4a
!igure 8.4b
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!igure 8.4b
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Te e%olution o' &ore cole) organis&s doesnot %iolate te second la( o' ter&odyna&ics
Entro#y 5disorder6 &ay decrease in an organis&,
but te uni%erse+s total entro#y increases
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Concept 8.': The free4energy change of areaction tells us #hether or not the reactionoccurs spontaneously
7iologists (ant to $no( (ic reactions occur
s#ontaneously and (ic reuire in#ut o' energy
To do so, tey need to deter&ine energy canges
tat occur in ce&ical reactions
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-ree4Energy Change! G
- li%ing syste&+s free energy is energy tat cando (or$ (en teerature and #ressure are
uni'or&, as in a li%ing cell
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Te cange in 'ree energy 5G6 during a #rocessis related to te cange in ental#y, or cange in
total energy 5H 6, cange in entro#y 5S6, and
teerature in Kel%in units 5T 6
G = H− T S
$nly processes #ith a negati2e 5G are
spontaneous and! spontaneous processes can
be harnessed to perform #or3
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-ree Energy! *tability! and E6uilibrium
!ree energy is a &easure o' a syste&+s instability,its tendency to cange to a &ore stable state
3uring a s#ontaneous cange, 'ree energy
decreases and te stability o' a syste& increases
Euilibriu& is a state o' &a)i&u& stability
- #rocess is s#ontaneous and can #er'or& (or$
only (en it is &o%ing to(ard euilibriu&
!igure 8.9
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7 More free energy 0higher G
7 Less stable7 reater #or3 capacity
7 Less free energy 0lo#er G 7 More stable7 Less #or3 capacity
0a ra2itational motion 0b ,iffusion 0c Chemical reaction
The free energy of the
system decreases
0∆G
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7 More free energy 0higher G 7 Less stable7 reater #or3 capacity
7 Less free energy 0lo#er G 7 More stable7 Less #or3 capacity
The free energy of the
system decreases
0∆G
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0a ra2itational motion 0b ,iffusion 0c Chemical reaction
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-ree Energy and Metabolism
Te conce#t o' 'ree energy can be a##lied to tece&istry o' li'e+s #rocesses
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Exergonic and Endergonic Reactions inMetaolism
-n eergonic reaction #roceeds (it a netrelease o' 'ree energy and is s#ontaneous
-n endergonic reaction absorbs 'ree energy 'ro&
its surroundings and is nons#ontaneous
!igure 8.:Eergonic reaction: energy released0a
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Eergonic reaction: energy released!
spontaneous
Endergonic reaction: energy re6uired!
nonspontaneous
0a
0b
- r e e e n e r g
y
- r e e e n e r g y
)eactants
)eactants
Energy
Energy
&roducts
&roducts
Amount of
energy
released
0∆G 9
&rogress of the reaction
&rogress of the reaction
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E!"iliri"m and Metaolism
;eactions in a closed syste& e%entually reaceuilibriu& and ten do no (or$
!igure 8.
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∆G
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/ells are not in euilibriu& tey are o#en syste&se)#eriencing a constant 'lo( o' &aterials
A defining feature of life is that metabolism is
ne2er at e6uilibrium
- catabolic #at(ay in a cell releases 'ree energy
in a series o' reactions 5li$e cellular res#iration6
!igure 8.8
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0a An open hydro4
electric system
0b A multistep open hydroelectric system
∆G
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Concept 8.(: AT& po#ers cellular #or3 bycoupling eergonic reactions to endergonicreactions
- cell does tree &ain $inds o' (or$
/e&ical
Trans#ort
ecanical
To do (or$, cells &anage energy resources by
energy coupling, te use o' an e)ergonic #rocess
to dri%e an endergonic one
ost energy cou#ling in cells is &ediated by -TP
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The *tructure and /ydrolysis of AT&
AT& 0adenosine triphosphate is te cell+senergy suttle
-TP is coosed o' ribose 5a sugar6, adenine
5a nitrogenous base6, and tree #os#ate grou#s
!igure 8.=
Adenine
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0a The structure of AT&
0b The hydrolysis of AT&
Adenosine triphosphate 0AT&
)ibose
Adenine
Triphosphate group
0( phosphate groups
Adenosine diphosphate
0A,&
Energy
Inorganic
phosphate
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;ideo: *pace4-illing Model of AT&
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;ideo: *tic3 Model of AT&
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Te bonds bet(een te #os#ate grou#s o' -TP+s tail can be bro$en by ydrolysis
Energy is released 'ro& -TP (en te ter&inal
#os#ate bond is bro$en
This release of energy comes from the
chemical change to a state of lo#er free
energy! not from the phosphate bonds
themsel2es
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/o# the /ydrolysis of AT& &erforms
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-TP dri%es endergonic reactions by#os#orylation, trans'erring a #os#ate grou# to
so&e oter &olecule, suc as a reactant
Te reci#ient &olecule is no( called a
phosphorylated intermediate
!igure 8.10
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0a lutamic acid con2ersion to glutamine
0b Con2ersion reaction coupled #ith AT& hydrolysis
0c -ree4energy change for coupled reaction
lutamic acid Ammonia lutamine
lutamin
e
lutamic acid &hosphorylated
intermediate
lu
=/(
lu
=/'
=/(
=/'
luluA,& &
i
A,& &i
=/'
lu
∆G AT& = >?.( 3cal@mol
∆G lu = +(.
3cal@mol
∆G lu = +(.
3cal@mol+ ∆G AT&= >?.( 3cal@mol
= >(.B 3cal@mol=et ∆G
=/(
lu AT&
AT&
∆G lu = +(.
3cal@mol
lu
1 '&A,&
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Trans#ort and &ecanical (or$ in te cell are also#o(ered by -TP ydrolysis
-TP ydrolysis leads to a cange in #rotein sa#e
and binding ability
!igure 8.11
T t t i * l t
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Transport protein *olute
*olute transported
0a Transport #or3: AT& phosphorylates transport proteins.
Mechanical #or3: AT& binds nonco2alently to motor
proteins and then is hydroly%ed.
&rotein and 2esicle mo2edMotor protein
Cytos3eletal trac3
AT&AT&
A,& & i
A,& & i
& i&
AT&
0b
;esicle
Th ) ti f AT&
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The )egeneration of AT&
-TP is a rene(able resource tat is regenerated
by addition o' a #os#ate grou# to adenosine
di#os#ate 5-3P6
Te energy to #os#orylate -3P co&es 'ro&
catabolic reactions in te cell
The AT& cycle is a re2ol2ing door through
#hich energy passes during its transfer from
catabolicto anabolic path#ays
!igure 8.12
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Energy from
catabolism
0eergonic! energy4releasing processes
Energy for cellular
#or3 0endergonic
energy4consumingprocesses
A,& & i
/'$AT&
C t 8 E d t b li
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Concept 8.: En%ymes speed up metabolicreactions by lo#ering energy barriers
- catalyst is a ce&ical agent tat s#eeds u# a
reaction (itout being consu&ed by te reaction
-n en%yme is a catalytic #rotein
>ydrolysis o' sucrose by te en"y&e sucrase is
an e)ale o' an en"y&e?cataly"ed reaction 5ne)t
slide6
!igure 8.N02
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*ucrose
0C1'/''$11
lucose
0C/1'$
-ructose
0C/1'$
*ucrase
Th A ti ti E + i
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The Acti2ation Energy +arrier
E#ery chemical reaction etween molec"les
in#ol#es ond rea$ing and ond forming
Te initial energy needed to start a ce&ical
reaction is called te 'ree energy o' acti%ation,
or acti2ation energy 5E -6
-cti%ation energy is o'ten su##lied in te 'or& o'
ter&al energy tat te reactant &olecules absorb
'ro& teir surroundings
!igure 8.1
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Transition state
)eactants
&roducts
&rogress of the reaction
EA
∆G
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Animation: /o# En%ymes
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/o# En%ymes *peed Dp )eactions
En"y&es cataly"e reactions by lo(ering te
E - barrier
En"y&es do not a''ect te cange in 'ree energy
5G6 instead, tey asten reactions tat (ould
occur e%entually
!igure 8.14
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Course of
reaction
#ithouten%yme
Course of
reaction
#ith en%yme
EA #ith
en%yme
is lo#er
EA
#ithout
en%yme
&roducts
)eactants
- r e e e n
e r g y
5G is unaffected
by en%yme
&rogress of the reaction
*ubstrate *pecificity of En%ymes
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*ubstrate *pecificity of En%ymes
Te reactant tat an en"y&e acts on is called
te en"y&e+s substrate
Te en"y&e binds to its substrate, 'or&ing an
en%yme4substrate comple
The reaction cataly%ed by each en%yme is
2ery specific
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Te acti2e site is te region on te en"y&e
(ere te substrate binds
Induced fit o' a substrate brings ce&ical grou#s
o' te acti%e site into #ositions tat enance teir
ability to cataly"e te reaction
!igure 8.19
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*ubstrate
Acti2e site
En%yme En%yme4substrate
comple
;ideo: Closure of /eo3inase ;ia Induced -it
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;ideo: Closure of /eo3inase ;ia Induced -it
Catalysis in the En%ymes Acti2e *ite
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Catalysis in the En%yme s Acti2e *ite
In an en"y&atic reaction, te substrate binds to
te acti%e site o' te en"y&e
Te acti%e site can lo(er an E - barrier by
rienting substrates correctly
*training substrate bonds
Pro%iding a 'a%orable &icroen%iron&ent
/o%alently bonding to te substrate
!igure 8.1:?1
1 '
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*ubstrates enter
acti2e site.
*ubstrates
*ubstrates are
held in acti2e
site by #ea3
interactions.
1 '
En%yme4substrate
comple
!igure 8.1:?2
* b t t t * b t t1 '
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*ubstrates enter
acti2e site.
*ubstrates
*ubstrates are
con2erted to
products.
*ubstrates are
held in acti2e
site by #ea3
interactions.
1 '
En%yme4substrate
comple
(
!igure 8.1:?
* b t t t * b t t1 '
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*ubstrates enter
acti2e site.
*ubstrates
*ubstrates are
con2erted to
products.
*ubstrates are
held in acti2e
site by #ea3
interactions.
1 '
&roducts are
released.
En%yme4substrate
comple
&roducts
(
!igure 8.1:?4
* b t t t * b t t1 '
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*ubstrates enter
acti2e site.
*ubstrates
*ubstrates are
con2erted to
products.
*ubstrates are
held in acti2e
site by #ea3
interactions.
1 '
&roducts are
released.
En%yme
En%yme4substrate
comple
Acti2e site
is a2ailable
for ne#
substrates.
&roducts
(
Effects of Local Conditions on En%yme Acti2ity
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Effects of Local Conditions on En%yme Acti2ity
-n en"y&e+s acti%ity can be a''ected by
@eneral en%iron&ental 'actors, suc as
teerature and #>
/e&icals tat s#eci'ically in'luence te en"y&e
Effects of Temperat"re and p%
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Effects of Temperat"re and p%
Eac en"y&e as an o#ti&al teerature in (ic
it can 'unction
Eac en"y&e as an o#ti&al #> in (ic it can
'unction
#ti&al conditions 'a%or te &ost acti%e sa#e 'or
te en"y&e &olecule
!igure 8.1<$ptimal temperature for
typical human en%yme
$ptimal temperature for
en%yme of thermophilic
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typical human en%yme
0(? C
$ptimal p/ for pepsin
0stomach
en%yme
$ptimal p/ for trypsin
0intestinal
en%yme
en%yme of thermophilic
0heat4tolerant
bacteria 0?? C
Temperature 0 C
p/9 1 ' ( ? 8 B 19
9 '9 9 9 89 199 1'9
0a $ptimal temperature for t#o en%ymes
0b $ptimal p/ for t#o en%ymes
) a t e o f r e
a c t i o n
) a t e o f r e a
c t i o n
&ofactors
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&ofactors
Cofactors are non#rotein en"y&e el#ers
/o'actors &ay be inorganic 5suc as a &etal in
ionic 'or&6 or organic
-n organic co'actor is called a coen%yme 4
coen%ymes include 2itamins
En'yme (nhiitors
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En'yme (nhiitors
Competiti2e inhibitors bind to te acti%e site
o' an en"y&e, coeting (it te substrate
=oncompetiti2e inhibitors bind to anoter #art o'
an en"y&e, causing te en"y&e to cange sa#e
and &a$ing te acti%e site less e''ecti%e
Examples of inhibitors include toxins, poisons,
pesticides, and antibiotics
!igure 8.18
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0a =ormal binding 0b Competiti2e inhibition 0c =oncompetiti2einhibition
*ubstrate
Acti2e site
En%yme
Competiti2einhibitor
=oncompetiti2e
inhibitor
Concept 8 : )egulation of en%yme acti2ity
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Concept 8.: )egulation of en%yme acti2ityhelps control metabolism
/e&ical caos (ould result i' a cell+s &etabolic
#at(ays (ere not tigtly regulated
- cell does tis by s(itcing on or o'' te genes
tat encode s#eci'ic en"y&es or by regulating
te acti%ity o' en"y&es
Allosteric )egulation of En%ymes
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Allosteric )egulation of En%ymes
Allosteric regulation &ay eiter inibit or
sti&ulate an en"y&e+s acti%ity
-llosteric regulation occurs (en a regulatory
&olecule binds to a #rotein at one site and
a''ects te #rotein+s 'unction at anoter site
)llosteric )cti#ation and (nhiition
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)llosteric )cti#ation and (nhiition
ost allosterically regulated en"y&es are &ade
'ro& #oly#e#tide subunits
Eac en"y&e as acti%e and inacti%e 'or&s
Te binding o' an acti%ator stabili"es te acti%e
'or& o' te en"y&e
Te binding o' an inibitor stabili"es te inacti%e
'or& o' te en"y&e
!igure 8.20
0a Allosteric acti2ators and inhibitors 0b Cooperati2ity: another type
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*tabili%ed
acti2e form
Inacti2e form
$scillation
=on4
functional
acti2e site
)egulatory
site 0one
of four
Allosteric en%yme
#ith four subunitsActi2e site
0one of four
Acti2e form
Acti2ator
*ubstrate
*tabili%ed
acti2e form
Inhibitor Inacti2e form *tabili%ed
inacti2e form
of allosteric acti2ation
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Cooperati2ity is a 'or& o' allosteric regulation
tat can ali'y en"y&e acti%ity
ne substrate &olecule #ri&es an en"y&e to act
on additional substrate &olecules &ore readily
/oo#erati%ity is allosteric because binding by a
substrate to one acti%e site a''ects catalysis in a
di''erent acti%e site
Feedac$ (nhiition
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Feedac$ (nhiition
In feedbac3 inhibition, te end #roduct o' a
&etabolic #at(ay suts do(n te #at(ay
!eedbac$ inibition #re%ents a cell 'ro& (asting
ce&ical resources by syntesi"ing &ore #roduct
tan is needed
!igure 8.21Acti2e site a2ailable Threonine
in acti2e site
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Isoleucine
used up by
cell
Isoleucine
binds to
allosteric
site.
Acti2e
site no
longer
a2ailableF
path#ayis halted.
En%yme 1
0threonine
deaminase
-eedbac3
inhibition
Intermediate A
Intermediate +
Intermediate C
Intermediate ,
En%yme '
En%yme (
En%yme
En%yme
End product
0isoleucine
Locali%ation of En%ymes
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y
*tructures (itin te cell el# bring order to
&etabolic #at(ays
*o&e en"y&es act as structural coonents
o' &e&branes
In eu$aryotic cells, so&e en"y&es reside in
s#eci'ic organelles 'or e)ale, en"y&es 'or
cellular res#iration are located in &itocondria
!igure 8.22
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Mitochondria
The matri contains
en%ymes in solution that
are in2ol2ed on one stage
of cellular respiration.
En%ymes for another
stage of cellular
respiration are
embedded in the
inner membrane
1 G m
!igure 8.N0b
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!igure 8.N09
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