2.5 Enzymes
Understanding:
- Enzymes have an active site to
which specific substrates bind
- Enzyme catalysis involves
molecular motion and the
collision of substrates with the
active site
- Temperature, pH and substrate
concentration affect the rate of
activity of enzymes
- Enzymes can be denatured
- Immobilized enzymes are widely
using in industry
Applications:
- Methods of production of lactose-free
milke and its advantages
Nature of science:
- Experimental design: accurate
quantitative measurements in
enzymes experiments require
replicates to ensure reliability
Skills:
- Design of experiments to test the
effect of temperature, pH and
substrate concentration on the activity
of enzymes
- Experimental investigation of a factor
affecting enzyme activity
Enzyme structure
Proteins that work as a catalyst.
Speed up chemical reactions without being
altered themselves.
Enzyme structure
Enzymes only catalyse one reaction
Thousands of reactions take place in a cell
Majority need to be catalysed.
Organisms produce thousands of enzymes
Enzymes are specific
Specificity
Enzymes have an active site
Specific to a substrate
Only that substrate can fit
Cannot catalyse other reactions
Three stages
1. Substrate binds to active site of enzyme.
2. Substrates change into different chemical
substances
3. These products separate from the active site,
leaving it vacant for substrates to bind again
Collisions
Random movement of substrates and enzymes
Means there are collisions
Only bind together if they are aligned exactly
Dissolving in water allows more collisions
Denaturation
Structure can be irreversibly altered by certain
conditions.
Active site shape changes – substrate can no
longer bind
Immobilised enzymes
Enzymes can be commercially used
Immobilised enzymes
Attach enzymes to another material or into
aggregations
Enzyme movement is restricted
What are the advantages?
Extension: How is lactose-free milk produced
using enzymes?
Your experiment on Monday
Each of you will be investigating the following
factors affecting the rate of reaction of enzymes.
- Temperature
- pH
- Concentration of substrate
Exploration
20% of final mark is your IA
Part of this is the exploration:
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Research question
Background information
Context
Equipment
Method
Risk Assessment
Variables
Complete the experiment
Write the exploration
Hand in: Tuesday 29th Sept
Look at the criteria to see
what is expected of you.
How is the rate of reaction of enzymes
affected by the different factors.
Design an experiment that
you will do in the second
lesson.
This needs to be complete
by the second lesson so
you have time to do the
experiment!
Yeast solution (enzyme)
1% Hydrogen peroxide
solution (substrate)
Buffer solutions (pH 1
Hydrochloric acid, pH 7
distilled water, pH 14 sodium
hydroxide)
Stop watch
Ice bath
Water baths - 30, 40, 50
degrees
Thermometer