Enzymes Models Of Action

18th October

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

Lock and Key

Lock and Key However certain substances can bind to the enzyme at sites other than the Active 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 E +S

enzyme-substrate complex ES

Enzyme reactions enzyme + substrate

enzyme-substrate complex

E +S

ES

enzyme-substrate complex ES

enzyme + product E +P

Enzyme activity How fast an enzyme is working Rate of Reaction

Enzyme activity How fast an enzyme is working Rate of Reaction Rate of Reaction = Amount of substrate changed (or amount product formed) in a given period of time.

Rate of Reaction

Enzyme activity

Variable you are looking at

Enzyme activity

Four Variables

Enzyme activity Temperature Four Variables

pH Enzyme Concentration Substrate Concentration

Rate of Reaction

Temperature

Rate of Reaction

Temperature

0

10

20

30

40

50

60

Temperature

5- 40oC Increase in Activity

Rate of Reaction

40oC - denatures

0 <5oC - inactive

10

20

30

40

50

60

Effect of heat on enzyme activty If you heat the protein above its optimal temperature bonds break meaning the protein loses it secondary and tertiary structure

Effect of heat on enzyme activty

Denaturing the protein

Effect of heat on enzyme activty

Denaturing the protein ACTIVE SITE CHANGES SHAPE SO SUBSTRATE NO LONGER FITS Even if temperature lowered – enzyme

can’t regain its correct shape

Rate of Reaction

pH

Rate of Reaction

pH

1 2 3 4 5 6 7 8 9

pH

Rate of Reaction

Narrow pH optima

1

2

3

4

5

6

7

8

9

pH

Rate of Reaction

Narrow pH optima

WHY?

1

2

3

4

5

6

7

8

9

pH

Rate of Reaction

Narrow pH optima

Disrupt Ionic bonds - Structure Effect charged residues at active site

1

2

3

4

5

6

7

8

9

Rate of Reaction

Enzyme Concentration

Rate of Reaction

Enzyme Concentration

Enzyme Concentration

Rate of Reaction

Substrate Concentration

Rate of Reaction

Substrate Concentration

Substrate Concentration

Substrate Concentration

Rate of Reaction

Active sites full- maximum turnover

Substrate Concentration

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