A student investigates catalase, an enzyme that breaks down hydrogen peroxide (H2O2) into water and oxygen. Filter paper disks are soaked in liver extract (catalase source) and dropped into test tubes containing 3% H2O2 at five different temperatures: 5, 20, 35, 50, and 65 degrees Celsius. The student records the time (in seconds) for each disk to rise to the surface, propelled by O2 bubbles. Each temperature is tested in triplicate, and the mean rise time is converted to reaction rate (1/time). The pH is held constant at 7.0 and substrate concentration is held at 3% throughout.
Which factor is the independent variable in this experiment?
- A
pH of the buffer
- Bcheck_circle
Temperature of the H2O2 solution
- C
Time for the disk to rise
- D
Concentration of H2O2
Explanation
The student deliberately varies temperature across five levels (5-65 C); this is the independent variable. Rise time (or its reciprocal, rate) is the dependent variable, while pH and substrate concentration are controlled.