Enzymes. Enzymes are proteins that act as biological catalysts They lower the activation energy of a specific chemical reaction Catalysts – speed up the chemical reaction and are not changed by the reaction
An intricate pocket or cleft – a 3-dimensional entity – structurally tailored to accept a particular substrate
Only fits its particular substrate
The substrateplays a role in determining the final shape of the enzyme and that the enzyme is has some flexibility.
This explains why certain compounds can bind to the enzyme but do not react because the enzyme has been distorted too much.
Other molecules may be too small to induce the proper alignment and therefore cannot react.
Only the proper substrate is capable of inducing the proper alignment of the active site
Enzymes can be named according to the type of reaction that they catalyse
Some enzymes just have individualised names:
The best way to understand temperature, pH and substrate concentration effects is through paying with this game....
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From: GCSE Bitesize:26.08.12
Enzyme activity concentration effects is through paying with this game....
pHFactors which affect enzyme activity 2: pH
Optimum pH values
Denaturation is a change in the shape of an enzyme which prevents it from fulfilling its function.
Enzymes (and other proteins) can be denatured by heat, pH changes, or certain chemicals
NB: Denaturation is not the same as ‘killing’ – proteins and enzymes are not living things, so can’t be killed!
August 26th 2012
Substrate concentrationSubstrate concentration: Enzymic reactions
Investigate the effect of enzyme concentration on yeast (saccharomyces cerevesiae) catalase enzyme activity using quantitative methods
p. 44 of your IGCSE book
Does catalase concentration affect the rate at which catalase breaks down H2O2?
What is the hypothesis you are going to test?
How can we measure the rate at which catalase breaks down H2O2?
We will measure the rate of reaction between catalase and hydrogen peroxide indirectly by measuring the pressure change in a closed chamber, using a Vernier Gas pressure probe
3. Can you think of other factors that may affect enzyme activity?