The aim of my investigation is to see how pH affects the activity of potato tissue catalase, during the decomposition of hydrogen peroxide to produce water and oxygen. Catalase + 2H2O2 Catalase + 2H2O +O2
Catalase + Hydrogen Peroxide Catalase + Water + Oxygen
The independent variable in this investigation is pH. Each individual enzyme has it’s own pH characteristic. This is because the hydrogen and ionic bonds between –NH2 and –COOH groups of the polypeptides that make up the enzyme, fix the exact arrangement of the active site of an enzyme. It is crucial to be aware of how even small changes in the pH of an enzyme can affect activity until the enzyme will eventually become denatured.
The enzyme which is going to be used in this practical is catalase. Catalse is a very common enzyme which is found in almost all living and root vegetables such as, Celeriac and Potatoes. Catalase is a tetramer of four polypeptide chains, each over 500 amino acids long. It contains four porphyrin heme groups, which can explain why it suitable to catalyze hydrogen peroxide.
The dependant variable in my investigation is oxygen. There is a clear link between the independent and dependant variable. The enzyme catalase works at an optimum pH of 7. This means that the closer the pH is to 7, the faster oxygen will be produced. Also, as amount of substrate decreases, the rate at which the products are produced will also decrease. This is because there is a lot of substrate in the beginning of a reaction and therefore it is easier for the substrate to combine with the enzyme. But in time there will be more product than substrate which means it’s harder for the enzyme to combine with the substrate and as a result will take more time in combining with the substrate.
In this practical, I predict that as the pH gets closer
Bibliography: Essential AS Biology for OCR – Glenn and Susan Toole published 2004 http://academic.brooklyn.cuny.edu/biology/bio4fv/page/enz_and.htm http://www.google.co.uk/search?hl=en&sa=X&oi=spell&resnum=0&ct=result&cd=1&q=what+effects+enzyme+activity&spell=1 Biology: A Functional Approach, M.B.V Roberts, T.J. King, 1987