enzymeS POWERPOINT LEARNINGS BEST SOURCES

Enzymes

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EnzymesEnzymes

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What Are Enzymes?What Are Enzymes?
•Most enzymes are
Proteins Proteins ((tertiary
and quaternary
structures)
•Act as CatalystCatalyst to
accelerates a
reaction
•Not permanentlyNot permanently
changed in the
process

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EnzymesEnzymes
•Are specific for
what they will
catalyzecatalyze
•Are ReusableReusable
•End in –asease
-Sucrase-Sucrase
-Lactase-Lactase
-Maltase-Maltase

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How do enzymes Work?How do enzymes Work?
Enzymes work by
weakening weakening
bondsbonds which which
lowers lowers
activation activation
energyenergy

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EnzymesEnzymes
Free
Energy
Progress of the reaction
Reactants
Products
Free energy of activationFree energy of activation
Without Enzyme
With Enzyme

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Enzyme-Substrate ComplexEnzyme-Substrate Complex
The substancesubstance
(reactant) an
enzymeenzyme acts on
is the substratesubstrate
EnzymeSubstrate
Joins

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Active SiteActive Site
•A restricted regionrestricted region of an enzymeenzyme
molecule which bindsbinds to the substratesubstrate.
Enzyme
Substrate
Active
Site

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Induced FitInduced Fit
•A change in the
shapeshape of an
enzyme’s active
site
•Induced Induced by the
substrate

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Induced FitInduced Fit
•A changechange in the configurationconfiguration of an
enzyme’s activeenzyme’s active site site (H+ and ionic
bonds are involved).
•InducedInduced by the substratesubstrate..
Enzyme
Active Site
substrate
induced fit

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What Affects Enzyme Activity?What Affects Enzyme Activity?
•Three factors:Three factors:
1.1.Environmental ConditionsEnvironmental Conditions
2.2.Cofactors and CoenzymesCofactors and Coenzymes
3.3.Enzyme InhibitorsEnzyme Inhibitors

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1. Environmental Conditions1. Environmental Conditions
1. Extreme1. Extreme Temperature Temperature are the most are the most
dangerousdangerous
- - high tempshigh temps may denature (unfold) denature (unfold)
the enzyme. enzyme.
2.2.pHpH (most like 6 - 8 pH near (most like 6 - 8 pH near
neutral)neutral)
3.3.Ionic concentrationIonic concentration (salt ions) (salt ions)

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2. Cofactors and Coenzymes2. Cofactors and Coenzymes
•Inorganic substances Inorganic substances (zinc, iron)(zinc, iron) and
vitaminsvitamins (respectively) are sometimes need
for proper enzymatic activityenzymatic activity.
•Example:Example:
IronIron must be present in the quaternary quaternary
structurestructure -- hemoglobinhemoglobin in order for it to
pick up oxygen.pick up oxygen.

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Two examples of Enzyme Two examples of Enzyme
InhibitorsInhibitors
a. a. Competitive inhibitorsCompetitive inhibitors:: are
chemicals that resembleresemble an enzyme’s enzyme’s
normal substratenormal substrate and competecompete with it
for the active siteactive site.
Enzyme
Competitive inhibitor
Substrate

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InhibitorsInhibitors
b.b.Noncompetitive inhibitorsNoncompetitive inhibitors::
Inhibitors that do not enter thedo not enter the
active siteactive site, but bind tobind to another partanother part
of the enzymeenzyme causing the enzymeenzyme to
change its shapechange its shape, which in turn
alters the active sitealters the active site.
Enzyme
active site
altered
Noncompetitive
Inhibitor
Substrate

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