Session Two (1.5.2): Enzyme Investigation
Introduction
This investigation uses an enzyme found in almost all cells: catalase. It is a particularly fast acting enzyme and helps prevent cells from being harmed by hydrogen peroxide, which is formed in everyday chemical reactions within the cell. Make sure you read the instructions and safety advice carefully.
Experimental Skills
You now have an opportunity to carry out practical investigations to see how external factors affect the activity of the enzyme called catalase. Note that the names of enzymes always end in the
suffix –ase, as in ‘catalase’. Catalase is found in most cells and converts hydrogen peroxide to water and oxygen. Hydrogen peroxide is a corrosive liquid and causes damage to cells if not quickly broken down.
Hydrogen peroxide is classed as an oxidising agent (promotes fire, bleaches on contact), a corrosive liquid and is poisonous. The hydrogen peroxide solutions available to the public in chemist shops, etc. are much less harmful than commercial concentrations, but nonetheless all safety advice and procedures should be followed.
The hazard safety signs used for hydrogen peroxide are:
Credit: DESCON Safety Data Sheet page 1
There are two enzyme practicals you can try. Remember to review the Safety Guide . You can do one or both of the practicals:
EXPERIMENT - How Enzyme Action can be Affected Download EXPERIMENT - How Enzyme Action can be Affected
EXPERIMENT - Enzyme Download EXPERIMENT - Enzyme
If you do the How Enzyme Action Can Be Affected practical, complete a data table for your results and draw a graph. Once you have completed the practical or practicals, answer the Conclusion and Discussion questions.
Tasks
Complete the in-text questions on page 44. Check your answers.
Tip: much Biology practical work involves collecting gases, e.g., to monitor enzyme activity or monitor the rate of photosynthesis. You have seen two experiments in which the number of bubbles produced per minute has been calculated. In experimental work, if you are asked how to make your experiment more reliable, you must repeat it and calculate the mean.
If you are asked about accuracy, you must improve the method of counting bubbles. Using a gas syringe, described in the link below, is the most accurate way to do this and can be used in both enzyme and photosynthesis investigations. Gas syringes dispense with the process of counting bubbles being produced and instead record the total volume of gas produced. Make sure you consider this in your assignment.