Peroxidase Enzyme Lab Report

By Ryan Keeney and Marie Coates

                The purpose of this experiment was to test the effects of abiotic factors on the reactivity of hydrogen peroxidase, an enzyme present in all aerobic cells. This particular experiment tested the effects of different pHs on the enzyme's reactivity.

                 Our hypothesis was that if the pH is raised, then it will speed the reaction of the enzyme, and that lowering it would cause the reaction to slow. We chose this hypothesis because data which was already available indicated that this was true.

      Variables:

      Independent Variable: pH of enzyme solution

      Dependent Variable: Amount of gas produced by reaction

      Controlled Variables: Concentration of enzyme, temperature of enzyme, amount of enzyme, amount of substrate, amount of hydrogen peroxide,





       Materials used:

• 5-10 grams of freshly picked bindweed
• Mortar and pestle
• Distilled Water
• 1 mL Syringe
• Hydrogen Peroxide
• A paper towel square (for filtration)
• 10 Glass Test Tubes
• Test Tube Rack/Holder
• Safety Glasses
• pH Test Strips
• 2 mL of hydrochloric acid and sodium hydroxide
• Ruler
• Tape
• Stopwatch

       Procedure:

• Use mortar and pestle to grind bindweed + 25 mL of distilled water until bindweed is completely ground
• Filter out bindweed extract with paper towel
• Attach ruler to test tube with tape
• Mix 1 mL of enzyme with 1 mL of pH solution in test tube
• Add 1/2 mL of hydrogen peroxide
• Measure height of bubbles produced by reaction over time
• Repeat using other pH solutions and water

        Data and Results:
      
     

	Control Trial 1(in seconds)	Control Trial 2 (in seconds)	HCl Trial 1 (in seconds)	HCl Trial 2 (in seconds)	NaOH Trial 1 (in seconds)	NaOH Trial 2 (in seconds)
1st mm	22.08	25.15	38.68	30.71	20.5	22.5
2nd mm	26.89	28.31	X	X	37.6	33.1
3rd mm	37.42	52.84	X	X	55.6	50.4
4th mm	54.38	64.62	X	X	99.9	66.3
5th mm	X	X	X	X	138.6	109.7

               

In the experiment, the enzyme mixed with sodium hydroxide had the fastest reaction and produced the most oxygen gas. The enzyme mixed with the hydrochloric acid had the smallest reaction, and barely reached 1 millimeter of bubbles. The control trials had one of the quickest reactions, but they did not produce over 4 mm of oxygen gas. They all reached one millimeter within around the same amount of time, but the data points split off significantly afterwards. The acidic enzyme solutions petered out, while the control and sodium hydroxide had around the same reaction speed until around 3 mm, where the data points split off again. Overall, the enzyme mixed with the NaOH solution had the highest bubbles at 5 mm.

            Conclusions:
            From the data that we gathered, we can infer that raising the pH of the enzyme caused the enzyme to produce more gas faster. We can also infer that the enzyme’s reaction rate is lowered by decreasing the pH, which seems to support our initial hypothesis. Unfortunately, the data may not be completely accurate, as we were not able to perform as many trials as we would have liked to. If we were to repeat the experiment, we would try to perform more trials. Another issue was the fact that even though we followed the same procedure, the concentration of the extract may not have been quite consistent. Both the unreliability of the concentration of the extract as well as the measurement of gas through the height of the bubbles produced may have also affected the data.