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EnzymesEnzymes

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• A material that speeds up a chemical reaction or makes it possible. But, it does NOT become part of the reaction’s end product.

What’s a Catalyst?What’s a Catalyst?

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How is this important to

life?

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What Are Enzymes?What Are Enzymes?• Most enzymes are

Proteins Proteins ((tertiary and quaternary structures)

• Act as CatalystCatalyst• 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

-Salivary Amylase-Salivary Amylase

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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.

EnzymeSubstrate

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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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

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 Coenzymes**2. Cofactors* and Coenzymes**

• Inorganic substances* Inorganic substances* (zinc, iron)(zinc, iron) and vitamins**vitamins** 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 pick up oxygen.up oxygen.

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a. a. Competitive inhibitorsCompetitive inhibitors:: are chemicals that resembleresemble an enzyme’s normal substrateenzyme’s normal substrate and competecompete with it for the active siteactive site.

Enzyme

Competitive inhibitor

Substrate

3. Enzyme Inhibitors3. Enzyme Inhibitors

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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 partanother part of the enzymeenzyme causing the enzymeenzyme to change its shapechange its shape, which in turn

alters the active sitealters the active site.

Enzymeactive site altered

NoncompetitiveInhibitor

Substrate

Enzyme InhibitorsEnzyme Inhibitors

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How do enzymes Work?How do enzymes Work?

Enzymes work by weakening weakening bondsbonds which which lowers activation lowers activation energy.energy.