Temperature Effects on Pea Cellular Respiration: A Respirometry Study

In this laboratory experiment, we aim to measure the consumption of oxygen during cellular respiration by observing changes in gas volume within respirometers containing either germinating or nongerminating peas. Cellular respiration encompasses the processes involved in actively acquiring oxygen (O2) by an organism and utilizing metabolic chemical oxidation within cells to release energy from organic compounds. The equation for the complete oxidation of glucose illustrates the necessity of oxygen for this energy-releasing process.

C6 H12 O6 + 6 O2 -> 6 CO2 + 6 H20 + 686 kilocalories of energy/mole of glucose oxidized.

The chemical oxidation of glucose holds significance in understanding respiration measurement. This experiment focuses on measuring:

1. O2 consumption during glucose oxidation.
2. CO2 production during aerobic respiration.
3. O2 consumption and CO2 release during cellular respiration.

We will compare the relative volume of O2 consumed by germinating and nongerminating peas at two different temperatures. The produced CO2 during cellular respiration will be eliminated using potassium hydroxide, forming solid potassium carbonate through a chemical reaction: CO2 + 2 KOH -> K2CO3 + H2O.

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Consequently, changes in gas volume within the respirometer directly correlate with the amount of oxygen consumed.

The experimental setup involves six respirometers, each assessing the O2 consumption over time. To eliminate external factors affecting volume changes, one respirometer contains glass beads without peas, serving as a control for atmospheric pressure and temperature fluctuations. The water movement in the respirometer will indicate changes in volume due to O2 consumption, and measurements will be taken throughout the experiment. The conditions involve both room temperature and a lower temperature of 10 degrees Celsius, and the experiment will compare the O2 absorption between germinating and nongerminating peas under these conditions.

We hypothesize that at a warmer temperature, the peas will absorb more oxygen than at a cooler temperature. Additionally, germinating peas will exhibit higher oxygen absorption than nongerminating peas under both room temperature and 10-degree Celsius conditions.

This experiment seeks to provide insights into the respiratory activity of peas under varying temperature and germination conditions, shedding light on the factors influencing cellular respiration.

Begin by setting up both a room temperature bath and a 10-degree Celsius bath, allowing time for temperature adjustment. Add ice to the latter to reach the desired temperature. While the baths are equilibrating, take a 100-mL graduated cylinder and fill it with 50 mL of water. Introduce 25 germinating peas into the water and measure the displaced volume. Record this volume for 25 germinating peas. Transfer these peas to a paper towel; they will be used in respirometer 1.

Next, refill the graduated cylinder with 50 mL of water. Add 25 dried peas to the water, then include enough glass beads to match the volume of the expanded germinating peas. Remove the peas and beads, placing them on a paper towel; they will be used in respirometer 2.

Repeat the process by refilling the graduated cylinder with 50 mL of water. Determine the number of glass beads required to reach a column equivalent to that of the expanded germinating peas. Remove these beads, placing them on a paper towel; they will be used in respirometer 3.

Follow the same procedures to prepare a second set of germinating peas, dried peas + beads, and beads for respirometers 4, 5, and 6.

To assemble the six respirometers, obtain vials with stoppers and pipettes. Place absorbent cotton in the bottom of each vial and saturate it with 15% KOH using a dropper. Ensure the vials are dry inside and avoid getting KOH on the sides. Add a dry cotton wad on top of the KOH-soaked cotton, maintaining equal amounts for each respirometer.

Place the first set of germinating peas, dried peas + beads, and beads in vials 1, 2, and 3, respectively. Insert the stopper fitted with the calibrated pipette and add a weighted collar on each end of the vial. Repeat this process with the second set of materials for vials 4, 5, and 6. Make a masking tape sling for each water bath to hold the pipettes out of the water during a 7-minute equilibration period.

After the equilibration, immerse all six respirometers entirely in their respective water baths. Water will enter the pipettes briefly and then stop. If continuous movement occurs, check for leaks. Keep hands out of the water bath after the experiment begins, ensuring constant temperature maintenance.

Allow the respirometers to equilibrate for an additional 3 minutes, then record the initial water position in each pipette to the nearest 0.01 mL. Check and record the temperature in both baths in Table 5.1. Every 5 minutes for 20 minutes, record water positions in each pipette. Store this data in Table 5.1.
Table 1 Data: