ENZYMES NAME: CHEBET MILTON CONTACT: [email protected]@yahoo.com Subject: Biology Topic: Nutrition.

ENZYMES

• NAME: CHEBET MILTON• CONTACT: [email protected]• Subject: Biology• Topic: Nutrition

Learning objectives • Define enzymes• Classify enzymes• Describe the mode of enzyme action (lock and key

hypothesis)• Do the mouse mischief exercises at the end using

the given mice

Introduction to Enzymes

• What are enzymesbiological catalysts, protein in nature which speed up and control the rate of chemical reaction in living organisms

• Classification of enzymes– Intracellular enzymes.– Extracellular enzymes.

Enzyme Action

Learning objective: to describe different models forenzyme action and to investigate factors which control the rate of an enzyme reaction

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Lock and Key

Lock and Key

However certain substances can bind to the enzyme at sites other than theActive site and modify its activity (inhibitors/co-factors)

Idea that the enzyme is flexible

Induced Fit

Enzyme reactions

enzyme + substrate enzyme-substrate complex

Enzyme reactions

enzyme + substrate enzyme-substrate complex

E +S ES

Enzyme reactions

enzyme + productenzyme-substrate complex

E +PES

enzyme + substrate enzyme-substrate complex

E +S ES

Enzyme activity

How fast an enzyme is workingRate of Reaction

Enzyme activity

How fast an enzyme is workingRate of Reaction

Rate of Reaction = Amount of substrate changed (or amount product formed) in a given period of time.

Rat

e of

Rea

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n

Enzyme activity

Variable you are looking at

Enzyme activity

Four Variables

Factors affecting Enzyme activity

Four Variables

Temperature

pH

Enzyme Concentration

Substrate Concentration

Rat

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Temperature

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Temperature

0 20 30 5010 40 60

Rat

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Temperature

0 20 30 5010 40 60

40oC - denatures

5- 40oC Increase in Activity

<5oC - inactive

Effect of heat on enzyme activityIf you heat the protein above its optimal temperature

bonds break meaning the protein loses it secondary and tertiary structure

Effect of heat on enzyme activity

Denaturing the protein

Effect of heat on enzyme activity

Denaturing the protein

ACTIVE SITE CHANGES SHAPE SO SUBSTRATE NO LONGER FITS

Even if temperature lowered – enzyme can’t regain its correct shape

Rat

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pH

Rat

e of

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pH

1 3 42 5 6 7 8 9

Rat

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pH

1 3 42 5 6 7 8 9

Narrow pH optima

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e of

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pH

1 3 42 5 6 7 8 9

Narrow pH optima

WHY?

Rat

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pH

1 3 42 5 6 7 8 9

Narrow pH optima

Disrupt Ionic bonds - Structure

Effect charged residues at activesite

Rat

e of

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n

Enzyme Concentration

Rat

e of

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Enzyme Concentration

Enzyme Concentration

Rat

e of

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n

Substrate Concentration

Rat

e of

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ctio

n

Substrate Concentration

Substrate Concentration

Rat

e of

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ctio

n

Substrate Concentration

Substrate Concentration

Active sites full- maximum turnover

In this mischief exercise your are required to Highlight a word in the green (right hand) column and drag it into a middle box corresponding