Skip to 0 minutes and 10 seconds In this enzyme practical we are going to break down hydrogen peroxide using an enzyme called catalase. The enzyme is sometimes called peroxidase, that’s the same thing as catalase. Most cells make hydrogen peroxide (which is a poisonous waste product) so they need to produce catalase to break it down. You can use chopped celery, chopped potato, liver or another fresh living material as your source of catalase. We are going to use the fungus yeast. We’re using it in its dried form, which is sold for making bread. It’s easy to store and quick and clean to use. In this practical we will put the yeast into a cylinder of hydrogen peroxide.
Skip to 0 minutes and 58 seconds You will need to check the material you have chosen to use and the concentration of hydrogen peroxide that gives a reaction your students can see and measure. It is important, as with any practical, to do a risk assessment. Think about what concentration of hydrogen peroxide is suitable. Protect skin and clothing, for example, using eye protection and protective gloves. Check the health and safety guidance for your local area. Put 0.1g of yeast into 10ml hydrogen peroxide in a 50ml measuring cylinder. It is important to trial for yourself first to find the quantities that will give you a good set of results.
Skip to 1 minute and 43 seconds In this instance I am adding 0.1g of yeast into a 50ml measuring cylinder, but depending on the yeast you might find a different amount works better. You can see that the catalase, in the yeast cells, breaks down the hydrogen peroxide and makes bubbles of oxygen. We’re getting a froth of oxygen bubbles. You could do a simple experiment where you measure the height of froth. Or you can measure the volume of oxygen using equipment like this displacement equipment. Setting this up takes a bit of skill. Demonstrate to your students how to set it up and give them plenty of time to get used to using the technique.
Skip to 2 minutes and 28 seconds The yeast and hydrogen peroxide will go in here and the delivery tube takes the oxygen away to be collected. We have 10ml of hydrogen peroxide in the conical flask. Now put the yeast in. We are using a clear measuring cylinder and measuring the volume of oxygen, using the scale here. You can put a test tube here and measure the time for a test tube to fill. For demonstration purposes, you could use a gas cylinder, as shown here. These are more expensive, but have a scale to enable you to measure the volume of gas.
Catalase and hydrogen peroxide
This is our first video of three for you to watch as part of the learning objectives activity.
Hydrogen peroxide is the toxic by-product of respiration, and would cause cell damage if it were not quickly removed. Cells produce the enzyme catalase which breaks hydrogen peroxide down into two harmless substances - water and oxygen.
In this investigation, students can measure the rate of oxygen production using different concentrations of hydrogen peroxide.
Thinking about what you might want students to learn from this practical, how might the learning intention affect the equipment you choose to use?