18 th October Enzyme Action Learning objective to

18 th 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 = 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 p. H Enzyme Concentration Substrate Concentration

Rate of Reaction Temperature

Rate of Reaction Temperature 0 10 20 30 40 50 60

Temperature 5 - 40 o. C Increase in Activity Rate of Reaction 40 o. C - denatures 0 <5 o. C - 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 p. H

Rate of Reaction p. H 1 2 3 4 5 6 7 8 9

p. H Rate of Reaction Narrow p. H optima 1 2 3 4 5 6 7 8 9

p. H Rate of Reaction Narrow p. H optima WHY? 1 2 3 4 5 6 7 8 9

p. H Rate of Reaction Narrow p. H 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

Rate of Reaction Substrate Concentration

Rate of Reaction Substrate Concentration

Substrate Concentration Rate of Reaction Active sites full- maximum turnover Substrate Concentration