Write a lab report to help you summarize and organize your thoughts about your two investigations. In your lab report, tell how you conducted the investigations, what data you collected, and what you concluded.

Answer 1

Lab Report Summary

Title: Investigating the Effects of Light Intensity on Photosynthesis and the Impact of pH on Enzyme Activity

Introduction

This report summarizes two investigations conducted to explore the effects of environmental factors on biological processes. The first investigation examined how varying light intensity influenced the rate of photosynthesis in aquatic plants. The second investigation focused on the effect of different pH levels on enzyme activity, using catalase as the enzyme of interest.

Investigation 1: The Effect of Light Intensity on Photosynthesis

Objective

To determine how varying light intensities affect the rate of photosynthesis in Elodea plants using a qualitative measurement of oxygen production.

Materials

• Elodea plants
• Light source (lamp)
• Ruler
• Stopwatch
• Measuring cylinder (to measure water)
• Sodium bicarbonate solution (to provide CO2)

Methodology

1. Cut equal lengths of Elodea and place them in a measuring cylinder filled with water and a small amount of sodium bicarbonate.
2. Position the light source at varying distances from the plants to create different light intensity levels (e.g., 10 cm, 20 cm, 30 cm).
3. Allow the plants to acclimate for 5 minutes for each light distance.
4. Start a stopwatch and count the number of bubbles produced over a 5-minute period as a measure of oxygen production, representative of the photosynthesis rate.
5. Repeat the experiment three times for each light intensity to ensure reliability and record the results.

Data Collected

| Light Intensity (distance from light source) | Average Number of Bubbles (3 Trials) | |-----------------------------------------------|--------------------------------------| | 10 cm | 30 | | 20 cm | 20 | | 30 cm | 10 |

Conclusion

The results demonstrated a clear trend; as the light intensity decreased (with increased distance from the light source), the rate of photosynthesis (indicated by the number of bubbles) also decreased. This supports the hypothesis that light intensity is directly proportional to the rate of photosynthesis in Elodea plants.

Investigation 2: The Effect of pH on Enzyme Activity

Objective

To investigate how different pH levels affect the activity of catalase in breaking down hydrogen peroxide (H₂O₂) into water and oxygen.

Materials

• Fresh potato (source of catalase)
• Hydrogen peroxide solution
• pH buffer solutions (pH 4, 6, 7, 8, 10)
• Test tubes
• Stopwatch
• Measuring cylinder

Methodology

1. Prepare five test tubes, one for each pH level.
2. In each test tube, add 2 mL of the pH buffer followed by 2 mL of hydrogen peroxide.
3. Using a potato, cut equal-sized pieces (about 1 cm³) and place a piece into each test tube.
4. Quickly plug the test tubes and start the stopwatch to capture the reaction.
5. After 5 minutes, observe and measure the oxygen produced by noting the height of foam or using a gas syringe if available.
6. Repeat the experiment three times for each pH level for reliable data.

Data Collected

| pH Level | Average Volume of Oxygen Produced (mL) | |----------|-----------------------------------------| | 4 | 3 | | 6 | 5 | | 7 | 10 | | 8 | 7 | | 10 | 2 |

Conclusion

The experiment revealed that catalase activity is optimal at neutral pH (pH 7), where the highest volume of oxygen was produced. At extreme pH levels (both acidic and basic), the enzyme's activity significantly decreased. This confirms that pH levels can considerably influence enzyme functionality, supporting the hypothesis that enzymes have optimal activity ranges.

Overall Conclusion

Both investigations highlighted the importance of environmental factors on biological processes. The first experiment concluded that light intensity directly affects photosynthesis rates, while the second experiment demonstrated that pH significantly influences enzyme activity. These findings could have implications for understanding plant growth and enzyme-based reactions in various biological and ecological contexts. Future investigations could explore the impact of additional variables or use more sophisticated quantitative analysis techniques.