Grade 12 Biology (SBI 4U1)
Sept 14 2012
Lab: Effect of temperature and pH on catalase activity
Catalase is an enzyme that detoxifies chemicals that might harm the cell such as
peroxide (H2O2). The enzyme breaks H2O2 into water and oxygen. The production of the oxygen
gas bubbles serves as evidence that the catalase enzyme is working. As catalase is breaking the
bonds between H2O2, it is releasing energy in the form of heat which is reason for the warmth of
the bubbles during the reaction. Starch acts to trap these bubbles and this creates a
relatively stable foam that can be measured.
1. a) Describe the effect of damaging the potato on the catalase activity.
With the increased level of damage to the potato, there appeared to be more activity
within the reaction between the catalase and the H2O2.
b) Explain at the cell level why crushing or macerating the potato has this effect.
When you crush or macerate the potato, you are breaking the cell walls of each individual
cell. Once this happens, the catalase is released from the cells and is able to come
across the H2O2 much faster then if the potato and cell walls were kept whole.
2.a) Describe the effect of warm temperature (37ºC) compared to hot temperature (60ºC) on
Warm temperatures such as 37ºC produces a much higher activity level than hot
temperatures such as 60ºC.
b) Explain these observations based on the effect of heat on proteins.
- Warm temperatures increases the level of motion between the molecules, which
speeds up the reaction time due to more collisions happening more often and at a faster
pace between the enzyme and the substrate.
- Hot temperatures are too reactive and break the protein bonds, denaturing the enzymes
and changing the shape of the active sight. This preventing the substrate (H2O2) from...
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