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Enzymes are specialized ProteinsProteins

Act as CatalystsCatalysts to accelerate a reaction

Not permanentlyNot permanently changed in the process

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Are specific for what they will catalyzecatalyze

Are ReusableReusableEnd in –asease-Sucrase-Sucrase-Lactase-Lactase-Maltase-Maltase

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Enzymes work by weakening weakening bondsbonds which which lowers lowers activation activation energyenergy

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FreeEnergy

Progress of the reaction

Reactants

Products

Free energy of activationFree energy of activation

Without Enzyme

With Enzyme

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The substancesubstance (reactant) an enzymeenzyme acts on is the substratesubstrate

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EnzymeSubstrate Joins

A restricted regionrestricted region of an enzymeenzyme molecule which bindsbinds to the substratesubstrate.

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EnzymeSubstrate

Active Site

A change in the shapeshape of an enzyme’s active site

Induced Induced by the substrate

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A changechange in the configurationconfiguration of an enzyme’s activeenzyme’s active site site (H+ and ionic bonds are involved).

InducedInduced by the substratesubstrate..

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Enzyme

Active Sitesubstrate

induced fit

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. Extreme1. Extreme temperatures temperatures are the are the most dangerousmost dangerous- - high tempshigh temps may denature denature (unfold) (unfold) the enzyme. enzyme.

2.2. pHpH (most like 6 - 8 pH near (most like 6 - 8 pH near neutral)neutral)3.3. Substrate concentration- Substrate concentration- increasing substrate increases increasing substrate increases enzyme activity until levels are enzyme activity until levels are the same.the same.

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Inorganic substances Inorganic substances (zinc, iron)(zinc, iron) and vitaminsvitamins (respectively) are sometimes needed 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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a. a. Competitive inhibitorsCompetitive inhibitors:: are chemicals that resembleresemble an enzyme’s normal substrate enzyme’s normal substrate and competecompete with it for the active siteactive site.

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Enzyme

Competitive inhibitor

Substrate

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b. b. Noncompetitive inhibitorsNoncompetitive inhibitors::Inhibitors that do not enter thedo not enter the

active siteactive site, but bind tobind to another another partpart of theof the enzymeenzyme causing the enzymeenzyme to change its shapechange its shape, which in turn alters the alters the active siteactive site.

Enzymeactive site altered

NoncompetitiveInhibitor

Substrate