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Investigating The Effect of Substrate Concentration or Temperature On The Rate of Decomposition of Hydrogen Peroxide By Catalase In Immobilised Yeast

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M1-Investigating The Effect of Substrate Concentration or Temperature On The Rate of Decomposition of Hydrogen Peroxide By Catalase In Immobilised Yeast Problem: Hydrogen peroxide is a waste product of the metabolism (chemical reactions of living cells). It is a powerful oxidising agent, which would damage living cells unless it was destroyed. Hydrogen peroxide will eventually decompose into un-harmful substances such as water and oxygen however in this slow process. 2H O 2H O + O However the human body has a process which speeds up the breakdown of hydrogen peroxide. The human body produces an enzyme to speed up the breakdown of hydrogen peroxide; this enzyme is called catalase. Hypothesis: In my investigation I aim to explore one of the factors that would affect the catalysis of an enzyme; my research from textbooks, CD-ROMs (Encarta) and the Internet (www.britannica.com) tells me that factors such as; Temperature, pH, Substrate Concentration, Inhibition, Enzymes Cofactors and Enzyme concentration would greatly vary the rate of enzyme catalysis. However from this research I have decided substrate concentration (hydrogen peroxide) is the factor which would able my experiment to yield good conclusions. For this reason I have decided to look at how a change in temperature would affect the rate of a reactions. ...read more.


concentrations. Step 1: Prepare the alginate beads by mixing a solution of 3cm of yeast, 3cm of sodium alginate and 3cm of air. The yeast in this solution is the source of the catalase. I have decided to use the alginate as my source for the enzyme-in this way the enzyme is immobilised. I have decided to test these alginate balls with 11 varying concentrations of hydrogen peroxide and I will also test these 11 concentrations 5 times and take an average. Because of this I will make around 40 alginate balls providing that all these balls are evenly produced. In this stage I will wear goggles and if I spill some of the hydrogen peroxide concentration on my hands I will immediately wash them because hydrogen peroxide is highly corrosive. Step 2: Now I will test these alginate beads with each varying concentration of hydrogen peroxide. As an example, having picked an evenly prepared alginate ball I will drop it into the test tube containing a hydrogen peroxide concentration. With a stopwatch I will time from when I place the alginate bead into the concentration and time that it takes until the bead rises to float on the top of the hydrogen peroxide concentration. When I am timing the reaction I will have to be very responsive to keep my investigation accurate. ...read more.


In my experiment I used the same hydrogen peroxide concentrations for each of the 5 tests simply because there weren't enough test tubes and concentrations for the whole of the class to use. So in each test it could of meant that there would have been less and less hydrogen peroxide molecules in the concentration for the enzyme to react with ultimately meaning that the rate of reaction would have become slower and slower in each test. If I were to extend this investigation I would definitely use a different hydrogen peroxide concentration each time. I think that because I have measured the enzyme decomposition five times and have taken an average from this I feel my results are very reliable, the fact that I had repeated it 5 times means that any mistakes I made I could have looked at, rendered the mistake and repeated the test. Within the limits of how accurate I could keep my experiment I was very rigorous and because of this I feel I have managed to yield evidence to support the prediction that- if there are sufficient enzyme molecules, an increase in the substrate concentration, will produce an increase in the rate of reaction To improve my results I could start by testing the enzyme decomposition with a wider range of hydrogen peroxide concentrations as this would better my timings for the average rate of reactions. ...read more.

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