Aim: The aim of the Assessment Task 1 is to investigate the effect of 1)temperature, 2)pH and 3)substrate concentration on the action of enzyme such as catalase on hydrogen peroxide. Background knowledge: Enzymes are organic catalysts composed of proteins that assist organisms in facilitating metabolic reactions without undergoing any change themselves. Enzymes are sensitive to their environment and so must remain within a stable range of factors ( pH, temperature , substrate concentration etc) for them to function.
Any deviations from this stable state can result in decreased efficiency or even the denaturing (destruction) of the enzyme. What affects enzymes: 1)Temperature- Enzymes stop working if the temperature rises above 40? C. Increasing the temperature alters the 3D shape and so the enzyme can no longer fit the substrate. 2)pH- They work best in neutral conditions neither acidic nor alkaline. 3)Substrate concentration – Increasing the substrate concentration, increases the activiy of the enzymes till it reaches an optimal point beyond which there is no change in the enzyme acitivity.
Catalase Enzyme: The activity of an enzyme can be demonstrated using liver, which contains the enzyme, catalase. Hydrogen peroxide breaks down slowly to form water and oxygen. One molecule of Catalase can deal with six million molecules of Hydrogen Peroxide in 1 minute. This breakdown happens rapidly in the present of the Catalase and Oxygen gas evolves rapidly and can be tested with a glowing splint or rising bubbles (variable). Changes in the temperature, acidity (pH) and concentration of the hydrogen peroxide will affect the rate of the reaction.
The control was to have a test tube of just substrate without any enzymes present. The validity would be to test each variable in isolation without mixing any of the 3 variables namely, the pH, temp and substrate concentration. The amount of catalase and hydrogen peroxide will remain the same in all the test tubes. Hypothesis: The hypothesis is that since hydrogen peroxide breaks down into water and oxygen gas because of the enzyme, it is expected that with change in temperature of the catalase, oxygen bubbles would form.
Apparatus / Equipment used: -test tubes & test tube racks -pipettes -Tweezers -Ruler -Water baths (for temperature control) -Ice bucket -Thermometer -Beakers -Hotplates -Measuring cylinder -Vinegar -Bi-Carb Soda -pH paper -pH meters Paper towels to cover up spills -Pen and paper to record results Ingredients used: -Liver ( enzyme called catalase) -Hydrogen Peroxide Equipment setup: The test tubes were setup up in a test tube rack. Ice bucket to cool and hot water bucket to warm were also kept in readiness.
Experiment 1 (Temperature): Procedure: 1)I put on the work shirt, goggles, gloves and footwear as a safety measure. 2)I chopped up 3 equal pieces of liver. 3)I placed 1 piece of liver into one test tube each. 4)I prepared 3 test tubes each containing 10ml of hydrogen peroxide. 5)I setup a water baths with 100 Celcius temperature, for temperature control using the thermometer, to ensure the correct temperature was maintained. 6)I placed 2 test tubes containing liver and hydrogen peroxide each into the water bath. )When the correct temperature was reached, I quickly transferred the liver using tweezers into the test tube containing hydrogen peroxide from the same water bath 8)I looked for any oxygen bubbles rising up in the test tube and measured the rise using a ruler 9)I repeated the above steps with 350 Celcius temperature. 10)I repeated the above steps with 350 Celcius temperature. 11)I allowed the test tube contents to cool down before disposing off the liquid waste into the sink with plenty of water and the solid waste contents carefully into the appropriate bin. 12)I rinsed all apparatus used and dried them for future use.
Results of Experiment 1: It was observed that with 100 C, the temperature was too low and there was not enough heat for Catalase to catalyse the reaction well. At 350C temperature, the bubbles produced froth and it appeared like all the enzymes were catalyzing reactios. When the temperature rose to 500C, the bubbles went down, indicating that the temperature was too high, resulting in a breakdown of the enzyme called denaturation. The results when plotted resulted in a bell shaped curve. As temperature increases so to does the kinetic energy of the enzyme and substrate molecules which randomly collide.
The frequency of collisions increases as the temperature increases thus initially increasing the rate of reaction. This occurs up to a maximum rate of reaction and the temperature at which the maximum rate of reaction is reached is referred to as the optimum temperature. Beyond the optimum temperature, increasing temperature increases the kinetic energy of the molecules to the point that the three-dimensional shape of the enzyme can be lost. Thus the shape of its active site changes and can no longer bind to the substrate, reducing the rate of reaction beyond the optimum temperature.