I'm currently doing my A2 Level coursework - I am testing different quantities of copper sulphate and how it acts as an inhibitor on catalase.
I put copper sulphate and hydrogen peroxide in a test tube and then add a 10mmsquared cube of potato. I have a test tube bung with a flexible tube in it, running into a measuring beaker. I've tried to measure the amount of oxygen that ends up in the measuring tube but the amounts don't follow any pattern. With the first test I did, the most oxygen was produced when there was no copper sulphate in the test tube(my control group), then next was the one with 1 mole of copper sulphate, then 0.6 moles, 0.8 moles, 0.4 moles and the least oxygen produced was from the test tube with 2 moles of copper sulphate in it.
I did another test, the group with the most copper sulphate produced the most oxygen and the one with the least copper sulphate produced the least oxygen.
Surely this can't be right? Have you any idea what I might be doing wrong? Does copper sulphate only act as an inhibitor in certain conditions? Am I making a mess of my coursework? Thanks for your help.
It's difficult to say for certain what has gone 'wrong' without seeing you do the practical. What you might be encountering is just the normal variation that occurs with living material. Catalase is not necessarily evenly distributed in a potato and different potatoes will have different levels. That is why biological experiments have to be repeated (in a research situation, often 50-100 times) to pick up trends. Copper sulphate is an irreversible inhibitor and its action is not dependent on conditions.