Factors Affecting Enzyme Activity

Affect of pH on Enzymes


Enzymes are a type of protein that speed up chemical reactions. Even though enzymes are not destroyed during this process, their rate of reactions are affected by levels of pH. In this lab, we measured the rate of reaction of enzymes as they turned hydrogen peroxide into water and oxygen while being acted on by different pH levels.

Research Question

How will different pH levels affect the rate of reaction of enzymes turning hydrogen peroxide into water and oxygen?


Explanatory Hypothesis: A change in pH levels will lead to an affect on enzymatic activity.

Prediction: Increased pH levels will increase enzymatic activity.

Null Hypothesis: If pH levels change, the enzymatic activity won't be affected.

Alternative Hypothesis: Changes in pH levels will have an affect on enzymatic activity.


LabQuest- for putting together graphs and calculating pressure

3% Hydrogen peroxide- to be chemically reacted

test tubes- to hold the chemical reactions

pH Buffers- to see how pH affects enzyme activity

pipettes- to transfer liquids

water- to add to each test tube

enzyme mixture- to play the role as enzymes


A decrease in pH level will result in an increase in enzyme activity.


We first put 3 mL of 3.0% hydrogen peroxide and 3 mL of water in each of 3 test tubes after putting on goggles for eye protection. In the first tube 2 drops of pH 4 was added. In the second, 2 drops of pH 7. In the third, 2 drops of pH 10 was added. Using the LabQuest, we measured the rate of reaction when 2 drops of enzyme solution was added to each test tube. after 3 minutes the LabQuest would complete the graphs showing the rate of reaction as a result of the dependent variable (pressure) and the independent variable (time).


Once the data was collected, many patterns were seen by our group. The graphs proved that the optimal pH level was pH 4.


Big image
Big image


The main idea of this experiment was to calculate how changes in pH levels effect the reaction rate of enzymes. This lab proved that enzymes in pH 4 have the optimal rate of reaction. The reason for this is because pH 7 and pH 10 are too basic and anything lower than pH 4 would be too acidic. One way this experiment could have been improved is by not applying so much pressure to the test tube plug. Because we did this, the pressure in the test tube increased during the reaction causing a slight change in graphs. To extend this lab we could have seen the rate of reaction go down by putting the enzymes in an even more acidic test tube than pH 4.