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EnzymesEnzymes

EnzymesEnzymes

Enzyme ActionEnzyme Action

Factors Affecting Enzyme ActionFactors Affecting Enzyme Action

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EnzymesEnzymes

Catalysts for biological reactionsCatalysts for biological reactions Most are proteinsMost are proteins Lower the activation energyLower the activation energy Increase the rate of reactionIncrease the rate of reaction Activity lost if denaturedActivity lost if denatured May be simple proteinsMay be simple proteins

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Name of EnzymesName of Enzymes

End in –End in –asease Identifies a reacting substanceIdentifies a reacting substance

sucrase – reacts sucrosesucrase – reacts sucroselipase - reacts lipidlipase - reacts lipid

Describes function of enzymeDescribes function of enzymeoxidase – catalyzes oxidationoxidase – catalyzes oxidationhydrolase – catalyzes hydrolysishydrolase – catalyzes hydrolysis

Common names of digestion enzymes still Common names of digestion enzymes still use –use –inin

pepsin, trypsinpepsin, trypsin

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Enzyme Action: Enzyme Action: Lock and Key Model Lock and Key Model

An enzyme binds a substrate in a region called An enzyme binds a substrate in a region called the the active siteactive site

Only certain substrates can fit the active siteOnly certain substrates can fit the active site Amino acid R groups in the active site help Amino acid R groups in the active site help

substrate bindsubstrate bind Enzyme-substrate complex formsEnzyme-substrate complex forms Substrate reacts to form productSubstrate reacts to form product Product is releasedProduct is released

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Lock and Key ModelLock and Key Model

++ + +

E + S E + S ES complex E + ES complex E + PP

S

P

P

S

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Enzyme Action: Enzyme Action: Induced Fit Model Induced Fit Model

Enzyme structure flexible, not rigidEnzyme structure flexible, not rigid Enzyme and active site adjust shape Enzyme and active site adjust shape

to bind substrateto bind substrate Increases range of substrate Increases range of substrate

specificityspecificity Shape changes also improve catalysis Shape changes also improve catalysis

during reactionduring reaction

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Enzyme Action: Enzyme Action: Induced Fit Model Induced Fit Model

E + S ES complex E + P

S

P

P

SS

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Factors Affecting Enzyme Factors Affecting Enzyme Action: TemperatureAction: Temperature

Little activity at low temperatureLittle activity at low temperature Rate increases with temperatureRate increases with temperature Most active at optimum temperatures Most active at optimum temperatures

(usually 37°C in humans)(usually 37°C in humans) Activity lost with denaturation at high Activity lost with denaturation at high

temperaturestemperatures

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Factors Affecting Enzyme ActionFactors Affecting Enzyme Action

Optimum temperatureOptimum temperature

ReactionReactionRateRate

Low HighLow High

TemperatureTemperature

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Factors Affecting Enzyme Factors Affecting Enzyme Action: Substrate ConcentrationAction: Substrate Concentration

Increasing substrate concentration Increasing substrate concentration increases the rate of reaction increases the rate of reaction (enzyme concentration is constant)(enzyme concentration is constant)

Maximum activity reached when all of Maximum activity reached when all of enzyme combines with substrateenzyme combines with substrate

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Factors Affecting Enzyme ActionFactors Affecting Enzyme Action

Maximum activityMaximum activity

ReactionReaction

RateRate

substrate concentrationsubstrate concentration

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Factors Affecting Enzyme Factors Affecting Enzyme Action: pHAction: pH

Maximum activity at Maximum activity at optimum pHoptimum pH

Narrow range of activityNarrow range of activity

Most lose activity in low or high pHMost lose activity in low or high pH

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Factors Affecting Enzyme ActionFactors Affecting Enzyme Action

ReactionReaction

RateRate

Optimum pHOptimum pH

3 5 7 9 113 5 7 9 11

pHpH