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In this experiment I will be investigating the effect of temperature on the enzyme catalyse in yeast. I will find the optimum temperature of the catalyse when its breaking down the hydrogen peroxide onto water and oxygen.

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Enzymes Introduction In this experiment I will be investigating the effect of temperature on the enzyme catalyse in yeast. I will find the optimum temperature of the catalyse when its breaking down the hydrogen peroxide onto water and oxygen. Theory All living thing have enzymes in them, the enzymes act as catalysts; they speed up chemical reactions. The way they do this is firstly the enzyme fits perfectly round the substrate; this is called the lock and key theory. The enzyme then joins up with another enzyme that has a substrate in it and the substrates then join together to perform a chemical reaction. The enzymes also break down chemical bonds in the same way. In the case of a human body it does this most effectively at 37.5?C, this is called this the optimum temperature. If the enzyme is in an environment with a low temperature there is less kinetic energy and the kinetic theory tells us, as things get colder they move slower and collide less frequently, this will cause the chemical reaction to slow. As the temperature increases the enzymes atoms inside start to vibrate, the kinetic theory also tells us that as atoms get hotter they move more. So if the enzyme's molecules vibrate more the enzyme will change shape and so the substrate isn't going to fit perfectly into it properly, this is shown below. ...read more.


Apparatus 20ml of hydrogen peroxide, 10ml of yeast solution, water bath, conical flask, measuring cylinder, stopwatch, rubber tube, tray and rubber stopper with a hole. Method 1) Set apparatus up as above. 2) Set water bath to the right temperature. 3) Measure 20ml of hydrogen peroxide solution. 4) Measure 10ml of yeast solution. 5) Put both solutions in the water bath for 10 minutes 6) Fill measuring cylinder with water and make sure there are not air bubbles in it, stand it upright in the tray, which also has water in it. 7) After 10 minutes mix the solutions put the solutions in the conical flask stir twice and put rubber stopper on it. 8) Start the timer as soon as solutions are stirred and measure how much oxygen is given off after 60 seconds. 9) Repeat the experiment twice more. Fair Test To ensure my test is fair I will I will only change one thing at a time; the temperature. The amount of yeast and hydrogen peroxide solution will stay the same. Accurate To make sure my experiment is accurate I will repeat the experiment three times at each temperature and take an average to eliminate any possible errors. Number and Range I am going to use 34?C 36?C 38?C 40?C and 42?C, I have chosen these small range of temperatures because I want to find the optimum temperature and my preliminary results tell me the optimum temperature is around 40?C. ...read more.


My results are reliable; you can tell this if you look at my table you can see the results are very similar. For instance the results for 42?C after 603 seconds are 453, 463 and 443; this proves my method is reliable. The evidence I have obtained is good enough to support my conclusion because I found the optimum temperature, my preliminary work helped me with this, I found the number and range that enabled me to find the optimum temperature accurately and reliably. To extend my findings I could use more yeast or hydrogen peroxide in the experiment or I could have a stronger solution of either of the two. I could also use an enzyme other than catalyse such as lipase or protease, to see whether I get the same shaped curve. I have thought of several different way of measuring the oxygen that is produced by the reaction, I could count the amount of bubbles given off by the reaction but this could be slightly inaccurate because the bubble sizes could differ. Another way I could measure the oxygen by putting a syringe and measuring the amount of gas produced in mm3. I could also try to find the exact optimum temperature by doing a more narrow range. E.g. 37?C 37.5?C and 28?C to find the precise optimum temperature. Enzymes Jon Cade Page 1 of 5 ...read more.

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