Investigating Enzyme Activity
To investigate how the concentration of hydrogen peroxide effects the
rate of reaction of an enzyme (catalase)
These factors could effect the rate of reaction on an enzyme:
· Surface Area
pH - Enzymes function at different pH values. In neutral conditions
the amount of oxygen gas given of in an enzyme-catalysed reaction will
An enzyme is affected by how much acid or alkali is present. Many
enzymes work best in neutral conditions but some prefer acids and some
This graph shows that the enzyme activity reacts best at pH7 (neutral)
Concentration - In concentrated solution there are more collisions
between each particle, so the reaction occurs more quickly.
This graph shows that increasing the concentration increases the
Temperature - Reactions go faster as temperature rises. The rate of
reaction also increases as the temperature rises, but with
enzyme-catalysed reactions the reaction rate starts to decrease when
the temperature is above 40 C. This is because enzymes are proteins
and their structures start to damage above 40 C.
This graph shows that the enzyme activity reacts best at 40°C as the
enzyme starts to denature above 40°C
Surface Area - Reactions can react faster when solids are cut into
smaller pieces. This is because there is more surface area which is
The more surface area there is, the more collisions that take place
between particles so the reaction rate is much quicker.
This graph shows that small pieces react better than bigger pieces.
I will test the effects of changing the level of concentration. For
this variable I will use three different concentrations of hydrogen
peroxide with catalase (enzyme). I will change the concentration
whilst keeping the time, concentration of catalase and the volume of
hydrogen peroxide constant.
I will begin all my tests at a constant temperature (room temperature)
and I will repeat each test three times so I can obtain an average
Lock and Key Model
A catalyst is a substance which alters the rate of reaction without
being used up. Enzymes are the catalysts in biological processes. They
are large proteins that speed up chemical reactions. The enzyme forms
the active site from small numbers of amino acids.
The active site is the location on the enzyme where the substrate
collides and the reaction takes place. If the shape of and the
substrate do not match exactly then they do not bind. This makes sure
that the enzyme does not work with the wrong reaction.
Enzymes are not affected by the reaction, so when the products have
been released, the enzyme is ready to bind...