When organisms perform normal metabolic processes, hydrogen peroxide is often created as a byproduct. Hydrogen peroxide can be harmful to cells, however, so organelles known as peroxisomes release an enzyme known as catalase to break down hydrogen peroxide into water and oxygen.
2 H2O2 + catalase → O2 + 2 H2O
Emily wanted to perform an experiment to test how temperature affects the action of catalase. To do this, she obtained four identical test tubes and poured 5 mL of hydrogen peroxide into each tube. Then, she placed the tubes into separate incubators set at 5°C, 25°C, 35°C, and 45°C. She allowed the tubes to equilibrate at their respective temperatures for 20 minutes and then added exactly 1 mL of cold catalase to each tube. After three minutes, she added 6 mL of sulfuric acid to each tube to stop the reaction. Finally, she titrated each solution to determine the amount of hydrogen peroxide remaining in each tube.
Which of the following factors was allowed to change during Emily's experiment?
the amount of time each tube was allowed to equilibrate
the amount of sulfuric acid added to each tube
the amount of catalase added to each tube
the amount of hydrogen peroxide remaining in each tube
the temperature of each incubator