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What Factors affect the rate of enzyme reaction

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Investigating which factors affect the rate of enzyme reaction Introduction to practical: Enzymes are proteins that are able to catalyse the rate of reaction in a living organism. Each enzyme controls a particular reaction and is consistently re-used. In addition, they are affected by several factors, such as temperature, pH, concentration of enzyme and concentration of substrate. An enzyme that is common in living organisms is Catalase, which works to catalyse the decomposition of the mixture hydrogen peroxide to water and oxygen. This enzyme is known to have one of the highest reactions out of all; every second, one molecule of catalase is able to transfer 83,000 molecules of hydrogen peroxide into water and oxygen. When hydrogen peroxide is broken down by catalase, oxygen and water are released. In a catalysed enzyme reaction, molecules named substrates fit into the active site and form an enzyme-substrate complex, a concept which can be called the lock and key theory. As a result of this, while still attached to the enzyme, the substrate breaks down into sub-units (smaller molecules) and the product is released. Below is a diagram to illustrate clearly:1 In this practical, pH will be investigated to see how it affects the rate of enzyme reaction. We will use different levels of pH of acid and alkali to break down hydrogen peroxide, thus concluding which level of pH caused the rate of reaction to increase or decrease by calculating the amount of oxygen released, and justifying the reason for our results. ...read more.


2) With a pH meter, measure the pH of the acid. If the pH isn't as required, then add more acid to decrease, or more alkali (sodium hydroxide) to increase the pH of the solution. 3) Next, measure 10cm� of catalase2, and pour into the beaker with the solution. Mix, and pour into a new measuring cylinder to fill 10cm� of the new solution. 4) Then, pour the mixture of catalase and the acid-alkali solution into the side-arm flask. 5) Once this is done, clean the measuring cylinder and use it to measure 10cm� of hydrogen peroxide. Pour into the side-arm flask, quickly close with the bung and start timing for the reaction to start. Write down in a table the amount of oxygen released by counting the bubbles formed inside the measuring cylinder every 30 seconds for 2 minutes. 6) Use this methodology for all pH levels you have decided to investigate to see which pH affects the rate of enzyme reaction. Please note that each level of pH should be repeated twice in order to achieve more accurate results and calculating an average. Analysis: From my results, I can see that the catalase reacted exactly as I predicted. The catalase worked best at pH 7.0, and so the reaction rate was highest. ...read more.


We tried repeatedly, and after several tries, we managed to get a set of accurate results. These problems may have occurred due to the loss of oxygen before placing the bung quickly enough onto the side arm flask. Because since the moment all the substances are inserted inside the flask, the reaction has commenced; and from that time to the time the bung is put on, oxygen will have been lost, causing less bubbles to arise in the measuring cylinder. To take this experiment further, we could look at other factors which affect the rate of enzyme reaction, such as temperature, concentration of enzyme or concentration of substrate. Temperature is known to have around the same affects on the rate of reaction as pH does, with the optimum pH being 37�C (body temperature). And so, we could compare results between pH and temperature, to see the differences and similarities. Or, we could develop this practical with pH by focusing on the level of pH that gave us best results: from 6.8 to 7.2. Even though we are aware that 7.0 is the optimum pH for increasing the rate of reaction, we can also see that pH's 6.8 and 7.2 gave increasing results, and so we could focus on this area by performing the same experiment but looking at pHs 6.8, 6.9, 7.0, 7.1 and 7.2, in order to a greater accuracy in our results, and see the transition from 1 pH level to another. ...read more.

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