8/10/2019 Pengantar enzim
1/21
Chapter 5Enzymes, Coenzyme and
Energy
Biology 100
Spring 2009
8/10/2019 Pengantar enzim
2/21
Energy
All living things require energy
Nutrientsare one sour!e o" energy,as #ell as $eing mole!ules organisms
require to gro#, reprodu!e or repair Biochemical reactionsare the
pro!esses used "or the "ormation,
$rea%do#n and rearrangement o"mole!ules to provide organisms#ith energy
8/10/2019 Pengantar enzim
3/21
A!tivation Energy
Activation Energyis the requiredinput o" energy to ma%e area!tion start
8/10/2019 Pengantar enzim
4/21
Catalyst
A catalyst is a !hemi!al thatspeeds up the rea!tion $ut is notused up in the rea!tion
&o#ers the a!tivation energy neededto start a rea!tion
's not used up during the rea!tion
's un!hanged a"ter a rea!tion
8/10/2019 Pengantar enzim
5/21
Enzymes
Enzymes a!t as !atalystsEnzymes are proteins that speedup a rate o" rea!tion
(ound in !ells throughout the $ody &o#ers a!tivation energy
Enzymes #ill end in ase
S)EC'('C*
8/10/2019 Pengantar enzim
6/21
Enzymes
8/10/2019 Pengantar enzim
7/21
+o# Enzymes or%
Ea!h enzyme has a spe!i-! sizeand ./ shape
Ea!h enzyme is going to -t #ith a
!ertain substratemole!ule enzyme!onne!ts to
8/10/2019 Pengantar enzim
8/21
+o# Enzymes or%
hen the enzyme and su$strateare !onne!ted, it is %no#n asenzyme-substrate complex
3he binding site is #here theenzyme physi!ally atta!hes itsel"to the su$strate
3heactive site is #here theenzyme #ill !ause a spe!i-! parto" the su$strate to !hange
8/10/2019 Pengantar enzim
9/21
8/10/2019 Pengantar enzim
10/21
Co"a!tors4Coenzynes
Some enzymes need an additionalmole!ule to !arry out the pro!ess
Cofactorsare inorgani! ions or
organi! mole!ules that serve anenzyme helpers
Coenzymes are organi! mole!ulesthat "un!tion as a !o"a!tor ay $e !ertain amino a!ids, nitrogenous
$ases, and vitamins
8/10/2019 Pengantar enzim
11/21
Co"a!tors
8/10/2019 Pengantar enzim
12/21
3urnover 6um$er
3he num$er o" mole!ules o"su$strate #ith #hi!h a singleenzyme !an rea!t at a given time
e7 reactions/minute is %no#n asthe turnover number
Can $e quite large !ompared to
un!atalyzed rea!tions Can depend on the environment
8/10/2019 Pengantar enzim
13/21
Environment
3emperature !an have a hugeimpa!t on turnover rate
a higher temperate #ill in!rease the
rate o" mole!ular motion, to a !ertaine7tent
3oo high o" temperatures may !ausethe enzyme to !hange its shape, this
is %no#n as denaturing, #here aprotein stru!ture is permanently!hanged
8/10/2019 Pengantar enzim
14/21
Environment
!ptimum temperature is #henthe rate o" "ormation o" theenzyme/su$strate !omple7 is
"astest
8/10/2019 Pengantar enzim
15/21
Environment
p+ also a8e!ts the rate o"
enzyme/su$strate !omple7es ost enzymes have an optimum p+
o" around neutral +o#ever, some pre"er a!idi! or $asi!
!onditions
8/10/2019 Pengantar enzim
16/21
CompetitionCompetition
Enzymatic competition is #here thereare several %inds o" enzymes availa$leto !om$ine #ith the same %ind o"su$strate mole!ule3he su$strate a!etyl !an $e a!ted upon $y
three di8erent enzymes: !itratesynthetase, "atty a!id synthetase, andmalate synthetase
Fig.5.7,
pg.103
8/10/2019 Pengantar enzim
17/21
;ene
8/10/2019 Pengantar enzim
18/21
Fig.5.7,
pg
.103
8/10/2019 Pengantar enzim
19/21
'nhi$itor
%nhibitor is a mole!ule thatatta!hes itsel" to an enzyme andinter"eres #ith the enzymes
a$ility to "orm an enzyme/su$strate !omple7
Competitive 'nhi$ition
6egative/(eed$a!% 'nhi$ition
8/10/2019 Pengantar enzim
20/21
Competitive 'nhi$itionCompetitive 'nhi$ition 'n competitive inhibitionan
inhi$itor has a shape that is !loselyresem$ling the normal su$strate o"an enzyme
Enzyme $e!omes ine8e!tive
8/10/2019 Pengantar enzim
21/21
6egative/(eed$a!%6egative/(eed$a!%
'nhi$ition'nhi$ition 'n negative-feedbac& inhibitionis apro!ess #here the output o" asystem a!ts to oppose !hanges tothe input o" the system
Allosteric #egulation is theregulation o" an enzyme or otherprotein $y $inding an e8e!tormole!ule at the protein>s allosteri!site a site other than the a!tive site
http:44higheredm!gra#/hill!om4ol!4dl4120004$io10s#"