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Chapter 5Enzymes, Coenzyme and

Energy

Biology 100

Spring 2009


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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


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A!tivation Energy

Activation Energyis the requiredinput o" energy to ma%e area!tion start


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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


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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*


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Enzymes


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+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


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+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


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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


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Co"a!tors


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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


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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


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Environment

!ptimum temperature is #henthe rate o" "ormation o" theenzyme/su$strate !omple7 is

"astest


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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


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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


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;ene


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Fig.5.7,

pg

.103


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'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


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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


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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

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