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An Investigation Into The Factors That Effect Enzyme Controlled Reactions

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An Investigation Into The Factors That Effect Enzyme Controlled Reactions Introduction Enzymes are biological catalysts that carry out the thousands of chemical reactions that occur in living cells. In an enzyme-catalysed reaction, the substance to be acted upon, or substrate, binds to the active site of the enzyme. The enzyme and substrate are held together in an enzyme-substrate complex by hydrophobic bonds, hydrogen bonds, and ionic bonds. The enzyme then converts the substrate to the reaction products in a process that often requires several chemical steps, and may involve covalent bonds. Finally, the products are released into solution and the enzyme is ready to form another enzyme-substrate complex. As is true of any catalyst, the enzyme is not used up as it carries out the reaction but is recycled again and again. One enzyme molecule can carry out thousands of reaction cycles every minute. Each enzyme is specific for a certain reaction because its amino acid sequence is unique and causes it to have a unique three-dimensional structure. The "business" end of the enzyme molecule, the active site, also has a specific shape so that only one or few of the thousands of compounds present in the cell can interact with it. If there is a prosthetic group on the enzyme, it will form part of the active site. Any substance that blocks or changes the shape of the active site will interfere with the activity and efficiency of the enzyme. ...read more.


Both the gaining and losing of H+ electrons, this effects the enzyme and the shape is disrupted, the enzyme is denatured. Many enzymes have an optimum pH of neutral and are denatures at high and low pH. To test for the difference that pH has in an enzyme controlled reaction a range of pH's are needed. This is good pH range to use within a school laboratory; Hydrochloric Acid (pH 1, strong acid) Lemon juice (pH 4, weak acid) Distilled water (pH 7, neutral) Sodium Bicarbonate (pH 10-11, weak alkali) Sodium Hydroxide (pH 14, strong alkali) Concentration of Catalase The amount of catalase should alter how fast the reaction is taking place. The reaction should speed up when the concentration of the catalase increases. This is because there is more of the enzyme to take part in the reaction. If there was a very low concentration of catalase the reaction would take place, but just slower than at higher concentrations. Plan The idea of this experiment is to study the enzyme catalase, which accelerates the breakdown of hydrogen peroxide into water and oxygen. To do this I will alter one variable, this will be pH. I aim to find the effect that different pH's have on the efficiency of the enzyme. The way that I am going to measure how well the enzyme work in different pH, I am going to collect the oxygen gas that comes from the experiment. ...read more.


Fair Test To make this experiment a fair test I will need to keep all the variables the same except the one that I am investigating, pH. I will also need to repeat the test 4 times to ensure that there is a high level of accuracy and possible mistakes are spotted. Health and Safety The acids and alkalis that are used are not very dangerous, but if they come into contact with skin, eyes etc. they should be washed with water. Goggles and lab coats should be worn at all times, and hair should be tied back. All bags should be taken from the laboratory of put in a suitable place where they will not cause an accident. Recording the results To record the results I will use a table like this, one for each of the pH: Time (secs) 120 240 360 480 540 Oxygen Produced Method Take 10cm3 of hydrogen peroxide with 5 cm3 of distilled water, and place in a boiling tube. Set up the rest of the apparatus as shown in the diagram. Fill the measuring cylinder with water and place upside down in the water bath. Take the measurement of water from the measuring cylinder, then place 5cm3 of catalase in the boiling tube with the hydrogen peroxide. Take measurement every 2 minutes and record them on the table. After 10 minutes repeat the experiment again 5 times. Repeat this again with all of the different pH's (hydrochloric acid, lime water, sodium bicarbonate and sodium hydroxide). ...read more.

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