Lab Report Template and Example (Annotated)

Title: The Effect of Temperature on the Rate of Oxygen Production by Catalase in Potato Tissue

Abstract: This experiment investigated how temperature affects the activity of the enzyme catalase, which breaks down hydrogen peroxide into water and oxygen. Potato discs were placed in hydrogen peroxide at five temperatures from 10°C to 50°C, and the volume of oxygen produced in two minutes was measured by gas displacement. Oxygen production increased from 10°C to a peak at 40°C and fell sharply at 50°C. The results support the hypothesis that catalase activity rises with temperature up to an optimum, above which the enzyme is denatured.

Introduction: Enzymes are biological catalysts that lower the activation energy of reactions. Catalase, found in most living tissues, catalyzes the breakdown of hydrogen peroxide, a toxic by-product of metabolism. As temperature rises, molecules gain kinetic energy and collide more often, so reaction rate generally increases. However, above an optimum temperature, the bonds maintaining the enzyme's three-dimensional shape break, the active site changes shape, and activity falls. The aim of this experiment was to determine the effect of temperature on catalase activity. It was hypothesized that oxygen production would increase with temperature up to around 35 to 45°C and then decrease.

Method: Potato discs of equal size were cut with a cork borer and scalpel. For each temperature (10, 20, 30, 40 and 50°C), a boiling tube containing hydrogen peroxide solution was equilibrated in a water bath for five minutes. Five discs were added, the tube was sealed with a bung connected to an inverted measuring cylinder filled with water, and the volume of oxygen collected after two minutes was recorded. Each temperature was tested three times with fresh discs and peroxide. Disc size, number of discs, peroxide volume and concentration, and reaction time were kept constant.

Results: Table 1 shows the mean volume of oxygen produced at each temperature. Oxygen production increased steadily from 10°C to 40°C, where it reached its highest mean value, then decreased sharply at 50°C. Replicates were closest at 20°C and most variable at 50°C (Figure 1).

Temperature (°C)	Trial 1 (cm³)	Trial 2 (cm³)	Trial 3 (cm³)	Mean (cm³)
10	3.0	3.4	3.2	3.2
20	5.6	5.8	5.7	5.7
30	8.2	8.9	8.5	8.5
40	10.4	11.2	10.6	10.7
50	4.1	2.6	3.5	3.4

Table 1. Volume of oxygen produced by catalase in two minutes at five temperatures (illustrative data). Figure 1 would show mean volume against temperature with range bars.

Discussion: The results support the hypothesis. The increase from 10°C to 40°C is consistent with collision theory: higher temperatures increase the kinetic energy of enzyme and substrate molecules, so successful collisions occur more frequently. The sharp fall at 50°C suggests that the enzyme began to denature, as changes to its tertiary structure altered the active site. Because only five temperatures were tested, the true optimum could lie anywhere between 30°C and 50°C. The greater spread of results at 50°C may reflect uneven denaturation during the equilibration period. Sources of error included slight differences in disc thickness, oxygen escaping before the bung was fitted, and difficulty reading the meniscus. Using a gas syringe, testing at 5°C intervals between 30°C and 50°C, and measuring disc mass rather than size would improve reliability and precision.

Conclusion: Catalase activity in potato tissue increased with temperature up to 40°C and fell sharply at 50°C, indicating an optimum temperature in that region and denaturation above it.