Investigating the effect of changing substrate concentration on the activity of the enzyme catalase The aim of this experiment is to examine how the concentration of a substrate (hydrogen peroxide) affects the rate of reaction of an enzyme catalyse (found in liver cells) Research Question: how does changing the concentration of the substrate affect the rate of reaction of the enzyme catalyse? Hypothesis: As the concentration of the substrate increases, so does the rate of reaction until the reaction reaches a maximum rate.

Also, as the concentration of the substrate decreases, so does the rate of reaction of the enzyme catalyse. This happens because an increase in the concentration of the substrate means more energized molecules. This results in more frequent collisions between the active site of the enzyme and the substrate; therefore enzyme-substrate complexes are formed much faster and thus a higher rate in reaction occurs. however once all the active sites have been filled up, then increasing the substrate concentration beyond this point has no affect as there is no more 'space' for a reaction.

Prediction: If the concentration of hydrogen peroxide were to increase, then so would the rate of reaction of the enzyme catalyse. Method: 1. Slice 1. 00 gram of liver using the forceps provided. 2. Prepare a solution of the needed concentration. Ensure solution is 10 cm3 when mixed. 3. Fill a water bath. Fill up a 100 cm3 measuring cylinder with water. Flip over the measuring cylinder as to make sure all the water stays within the cylinder and no air bubbles are present in the cylinder.

Direct the delivery tube of the bong into the measuring cylinder in the water bath. 4. Place the 1. 00 gram of liver into a conical flask. 5. Pour the 10 cm3 of mixed solution of hydrogen peroxide and water into the conical flask. Immediately cover the conical flask with the head of the bong. Start the stopwatch. 6. After 30 seconds, take out the delivery tube. Measure the amount of oxygen gas collected. Record result in a table. 7. Repeat for a total of 5 trials. 8. Repeat step 1-7, for all concentrations.

Variables: Independent: Concentration of hydrogen peroxide Control: Volume of solution; mass of liver; time taken for reaction. Dependent: Rate of reaction - amount of gas collected after 30 seconds Data collection: Uncertainties of instruments used: * Top pan balance: ±0. 01 g * 100 ml Measuring Cylinder: ±0. 5 ml * 10 ml Measuring Cylinder: ±0. 1 ml * Stop watch: ±1 second Table of concentration solutions made: 10 cm3 used for each test. Concentration of substrate solution(H2O2) (%)| Volume of water( cm3)( ±0. 5 cm3)| Volume of Hydrogen peroxide(cm3)(± 0. 05 cm3)| 0%| 10. 0| 0. 0| 25%| 7. 5| 2. 5| 50%| 5. 0| 5. 0| 75%| 2. 5| 7. 5| 100%| 0. 0| 10. 0| Results: Hydrogen peroxide concentration (%)| Amount of gas produced(water displaced) after 30 seconds( ±1 sec)| Average of test results ( seconds) ±5 sec(sum of gas collected/5 tests)| | Test 1| Test 2 | Test 3| Test 4 | Test 5| | 0| 0| 0| 0| 0| 0| 0| 25| 19| 17| 18| 16| 19| 17. 8| 50| 25| 27| 29| 27| 28| 27. 2| 75| 35| 31| 33| 34| 33| 33. 2| 100| 42| 40| 39| 40| 41| 40. 4|