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Factors that Affect Catalase activity

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Bernadette Walsh February 2008 Factors that Affect Catalase activity: Introduction: The aim of this experiment is to find out how the rate of a typical enzyme-catalysed reaction varies with different factors. In this experiment, enzymes will be investigated by using Catalase. A certain factor will be chosen and altered, in order to observe the effect on the activity of the enzyme. The main roles of enzymes are to act as biological catalysts in order to generate movement, assist active transport, and are involved in the digestive systems of animals; breaking down macromolecules into smaller ones. Background Information: Enzymes An enzyme is a biological catalyst, which is found in all living organisms. All enzymes are globular proteins made of long chains of amino acids, which fold to form specific tertiary structures. The tertiary structure of an enzyme determines its function. �"Enzymes are large molecules that work by reacting with another compound (the substrate) to form a short-lived enzyme-substrate complex. This complex is formed at a particular part of the enzyme molecule, usually at its surface, known as the active site. The complex breaks down to form the product(s), leaving an uncharged enzyme molecule, which is then available to catalyse another cycle. At the active site the enzyme works by reducing the amount of energy required (activation energy) which substrate molecules need to have before they can undergo the chemical change concerned." There are two models, which explain enzyme activity, the lock-and-key model, and the induced-fit model. Please see diagrams of each in Fig 1 below. 2: Fig 1. The lock-and-key model basically shows a temporary attachment between the active site and the substrate. The substrate must be an exact fit with the active site for the reaction to occur. The basis for the induced-fit model is that the enzyme provides an alternative reaction pathway with a lower activation energy. After the enzyme binds to the substrate, the enzyme may change shape. ...read more.


Predicted Observations: The amount of oxygen produced will increase with increasing temperature. Once the optimum temperature for the enzyme has been reached, the amount of oxygen produced will stop increasing. As temperature continues to increase after the optimum temperature, the amount of oxygen will decrease, as after this point the enzyme will be denatured. Time and Temperature Factors: I will ensure these factors are controlled and will stay the same by using a thermometer and a stopwatch. I will time the amount of time the test tube is in the water bath and also the amount of time the hydrogen peroxide is in the test tube, to keep it constant throughout the experiment. The temperatures will be chosen before the experiment and will be constantly measured to ensure the water baths are at the right temperature. Apparatus: Clamp-Stand Heat-proof mat Bunsen Burner Tripod Gauze Tile 250 ml Beaker Test tube Test tube rack Manometer Stop watch Ruler Thermometer Syringe Cork borer Plastic tweezers Razor blade Potato Hydrogen peroxide solution Pen for glassware Safety goggles Water baths Ice Item Quantity Reason Justification Clamp-Stand 1 Holding test tube in place No alternatives. Heat-proof mat 1 Protects working surface from heat off Bunsen burner No alternatives. Bunsen Burner 1 To heat the water baths No alternatives. Tripod 1 Holding gauze & beaker above Bunsen burner No alternatives. Gauze 1 To hold the beaker above the Bunsen burner No alternatives. Tile 1 To protect working surface from the razor blade/ cork borer No alternatives. 250 ml Beaker 1 To act as a water bath No alternatives. Test tube 13 To hold potato disks, hydrogen peroxide and for the experiments to take place in. No alternatives. Test tube rack 1 To hold the test tubes and to ensure they don't fall off the working surface No alternatives. Manometer 1 To measures the amount of oxygen gas formed Gas syringe unavailable. ...read more.


lengths of potato should be changed from 5cm to 2cm, and cut into four pieces of 0.5 cm so a larger surface area is available. Climatisation: Due to the fact that the enzymes did not have enough time to change temperature, I have decided to increase the length of time the test tube is in the water bath from 1 minute to 3 minutes. Reaction time: The length of reaction time will increase; the hydrogen peroxide will be left in the test tube for 3 minutes instead of 1 minute. Temperatures: Higher temperatures to be tested, since an optimum temperature and denaturing point were not observed. Apparatus: Only 7 test tubes required instead of 13 test tubes. Final method: 1. Set up apparatus as shown below. 2. Using a cork borer and razor blade, cut 4 cylindrical sections of 0.5 cm of potato. 3. Place the 4 sections of potato into a test tube. 4. Half fill a beaker with water (to be used as a water bath) and heat/cool down, using a Bunsen burner/ice to get a temperature of 10�C. 5. Place the test tube in a water bath at 15�C, as shown below. 6. Leave the test tube in the water bath for 3 minutes. 7. Ensure water bath is at correct temperature and manometer and syringe are securely in the test tube. 8. Mark a starting position on the manometer, where the flouracine ends (on the side away from the Bunsen burner, to avoid any accidents which may occur). 9. Add 5ml of hydrogen peroxide to the test tube, using a syringe. 10. Start the stopwatch and time for three minutes. 11. After three minutes, mark the ending position on the manometer. 12. Using a ruler, measure the amount of oxygen produced by measuring the distance between the two points on the manometer. 13. Repeat steps 2 - 12, only using 25�C, 35�C, 45�C, 55�C, 65�C and 75�C water baths. 14. Clean test tubes. 15. Repeat steps 2 - 14 twice. ...read more.

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