Enzyme Lab Report

How does hydrogen peroxidase and pH level affect the speed of the reaction of bindweed?

Hypothesis: If the pH of the enzyme is raised, then it will speed the reaction of the enzyme, and lowering it will slow the reaction.

Our independent variable was pH and the dependent variable was the amount of oxygen that was produced by the reaction. Our controlled variables were the enzyme source, substrate concentration, temperature, same size test tubes, amount of Hydrogen Peroxidase, amount of water.

pH is known to affect the reaction rate of enzymes, so that is why our hypothesis is justified. (http://www.worthington-biochem.com/introbiochem/effectsph.html)

We chose this as the hypothesis because many sources prove this to be correct.

Materials:

• 5 to 10 grams of freshly picked bindweed vines with leaves (about 1 handful)
• Mortar and pestle
• Distilled water
• 1 mL syringe
• Hydrogen peroxide
• 1 Paper towel square (for filtration)
• 10 glass test tubes
• Test tube rack or holder
• Safety glasses
• pH test strips
• 1 mL of each pH solution
• Ruler

Procedure:

1. Get all the materials set up
2. Use the mortar and pestle to grind up the bindweed + 25 mL of water until it has been fully ground.
3. Pour one mL of enzyme extract into a test tube.
4. Add one mL of pH solution or water to test tube
5. Measure height of liquid in test tube before addition of hydrogen peroxide
6. Add 1 mL of hydrogen peroxide to test tube
7. Measure height of bubbles over time
8. Repeat with other pH solutions + 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 amount of oxygen gas. The enzyme mixed with the hydrochloric acid had the smallest reaction, and barely reached 1 millimeter of bubbles. Both of the control trials did not reach over 4 mm.  The control trials had one of the quickest reactions, but they did not produce over 4 mm of oxygen gas.

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.