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Inhibition of an Enzyme

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Inhibition of an Enzyme Aim: The aim of the experiment is to see which concentration of an inhibitor will work best on an enzyme. Theory: Inhibitors are molecules that bind to enzymes and block their activity. Many plants and animals naturally contain inhibitors. An example of a cellular enzyme inhibitor would be proteins that specifically bind to and inhibit an enzyme target. Polyphenol oxidase also known as tyrosinase is an enzyme present in apples and potatoes. Tyrosinase catalyses the production of melanin and other pigments from tyrosine by oxidation, like in the browning of pieces of sliced apples or potatoes. The chemical reaction is: Tyrosinase Tyrosine + oxygen Melanin + Water When an inhibitor, such as ethanol, is added the browning of the sliced apples or potatoes can be stopped. ...read more.


Thus, we should keep the pH-level constant by adding an indicator that would show if the pH-level gets changed. By reducing the level of oxygen, for instance by putting the sliced apples under water or vacuuming them, the outcome will also be affected. Therefore we should make sure the level of oxygen is constant. Adding certain preservatives such as sulphur dioxide will stop the oxidation process. These preservatives can only affect the outcome if they are added by us - they don't occur naturally in apples or potatoes. Of course, we will avoid adding preservatives. When more time is used, the more will the oxidation process take. Therefore we should use a stop watch to be aware of the time spent for the experiment. ...read more.


Add a drop of indicator to the different pieces. 3. Add 1.0 mL of ethanol to each of the pieces, except number 1 as this will be the control piece. 4. Remember to start the stop watch as soon as adding the ethanol and remember to stop after 15 min. 5. Stop the experiment after min. and compare the colour change of the different pieces by using a spectrophotometer. Recording Data: Table showing the relationship between the concentration of ethanol and the measured light intensity: Concentration of ethanol (%) Light intensity (A) 0 % 1 % 5 % 10 % 15 % 20 % * Which concentration gave the best inhibition of tyrosinase? * Explain why a certain concentration gives a better inhibition. * Make a graph showing the relationship between the concentration of ethanol and light intensity. Light intensity (A) Concentration of inhibitor (%) Amine Khadir Biology Page 1 of 4 ...read more.

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