Lab 7, Exercise 3: Effect of Temperature on the Rate of Aerobic Respiration

Objective

• Investigate how different temperatures affect the rate of respiration in germinated peas.
• Utilize CO2 output as an indicator of respiration rate.

Key Concepts

• Cellular Respiration: Both plants and animals undergo cellular respiration.
• Explanation for Experiment: Temperature variations will be applied to germinated peas to observe changes in respiration rate.

Experimental Setup

• Subject: Germinated peas in enclosed containers.
• Measurement Method: CO2 concentration monitored via a device that reports in parts per million (ppm).
• Temperature Conditions:
  • On ice (0°C)
  • Room temperature (24°C)
  • Incubator (45°C)

Procedure

1. Enclosure: Peas placed in a sealed container with CO2 monitor.
2. Temperature Setup:
   • Peas placed at different temperatures (ice bath, room temp, incubator).
3. CO2 Monitoring: Use Vernier monitors to measure CO2 output over time.
4. Establish Baseline:
   • Record baseline CO2 concentration with probes at room conditions (not in contact with peas).
5. Data Collection: Record CO2 levels every 5 minutes up to 20 minutes.
6. Data Calculation: Calculate increase in CO2 from baseline after each interval.

Experimental Observations

• Baseline Readings: Differences in CO2 concentration due to machine calibration variations.
• CO2 Levels at Various Time Intervals:
  • Recorded every 5 minutes.
  • Noted the increase in ppm relative to baseline.

Data Analysis

• Graphing:
  • Line Graph: Used to illustrate changes over time.
    • X-axis: Time (minutes)
    • Y-axis: Increase in CO2 level (ppm)
  • Bar Graph: Used for comparing CO2 increase at the 20-minute mark.
    • X-axis: Temperature (°C)
    • Y-axis: CO2 increase (ppm)

Conclusions

• Increased temperature results in higher respiration rates as indicated by CO2 output.
• Higher temperatures increase kinetic energy, causing faster molecular movement and reaction rates.
• There is a limit to temperature increases; excessive heat can denature enzymes, stopping the reaction.

Discussion Points

• Enzyme Denaturation: At elevated temperatures, enzyme activity can cease, halting respiration.
• Graph Interpretation: Different graphs for time-based vs. endpoint analysis.
• Experimental Variability: Importance of baseline readings due to machine inconsistencies.
• Effect of Temperature on Reaction Rates: General rule of increasing rates with temperature up to a point, then a sharp decline.

In-Class Participation Questions

1. Why is it important to take baseline readings when comparing results between different temperatures?
2. Would increasing the temperature always result in an increase in the rate of a reaction indefinitely? Why or why not?

These notes provide a concise overview of the experiment on the effect of temperature on respiration rates in peas, highlighting experimental setup, data collection, and analysis insights.