A Discussion of the Measurement Process for Cellular Respiration

Introduction

There are three ways cellular respiration could be measured.

1. Consumption of O2 (How many moles of oxygen are consumed in cellular respiration?)
2. Production of CO2 (How many moles of carbon dioxide are produced by cellular respiration?)
3. Release of energy during cellular respiration.

Problem

In this experiment, the relative volume of O2 consumed by germinating and non germinating (dry) peas at two different temperatures will be measured.

Background Information

The vial with glass beads alone will permit detection of any changes in volume due to atmospheric pressure changes or temperature changes.

Six respiratometers should be set up as follows:

Six Respiratometers Set Up at Different Temperatures with Different Contents

Hypothesis

If the temperature decreased then the respiration rate would decrease as well because the enzymes that mediate cell respiration rate slow down at decreased temperatures. Since enzymes have an optimal temperature that they function well in, if the temperature were to decrease then the enzyme reaction rate would slow down in accordance with the decrease in temperature. Therefore, the respiration rate would slow down.

Independent Variable: Temperature (degrees Celsius)

Dependent Variable: Rate of Respiration (mL of O2/minute)

Analysis

1. The data did support the hypothesis which suggested that if the temperature were to decrease then the respiration rate would decrease as well. For the Germinating Seeds in 25 degrees Celsius, the water level dropped from 0.91 mL to 0.64 mL over 20 minutes, meaning that this drop had a more significant difference than the drop from 0.92 mL to 0.80 mL in 10 degrees Celsius over 20 minutes. This observation could be again noticed in the Dry Peas where there was a drop from 0.92 mL to 0.85 mL in 25 degrees Celsius over 20 minutes and a drop from 0.91 mL to 0.85 mL in 10 degrees Celsius over 20 minutes. The data showed that more O2 was consumed in higher temperatures than in lower temperatures. The data was supported more for the Germinating Peas as the Dry Peas were fairly temperature independent. Because the Dry Peas are dead, it is probable that they cannot respire, explaining why the Dry Peas were more temperature independent than the Germinating Peas.

One experimental control was the beads. Since the beads don’t respire, they show outside factors that could’ve possibly affected the results, meaning that they are good indicators of confounding variables. Another experimental control was the Dry Peas. The Dry Peas were dead, meaning that they don’t respire as well. Notably, the Dry Peas data showed that Germinating Peas must be in the vial for significant O2 consumption. In addition, the Dry Peas provide a good control for comparison for the data of the Germinating Peas.

It was necessary to correct the readings because the beads went through no cellular respiration, while the Germinating Peas and the Dry Peas did. The change in the atmospheric pressure could have caused changes in the respiration rate in the beads and all of the vials, therefore, correcting the results provided the more accurate readings than the original readings.

KOH was responsible for removing the CO2 that formed during cellular respiration. Because the CO2 collected at the bottom, it had to be removed or the O2 consumed would not have shown as the CO2 would have replaced it.

The rate of respiration of the mammal would be greater because the mammal maintained a constant body temperature, while the reptile did not. Because a reptile was cold-blooded, the reptile’s body temperature was dependent on it’s environment. As the temperature decreased, so did the reptile’s body temperature which caused a decrease in the respiration rate. However, there would be no decrease or increase in the respiration rate of the mammal as it maintained a constant temperature.

The small mammal’s respiration rate would increase at lower temperatures since the body temperatures of mammals would not depend on the environment (they are warm-blooded). The mammal must maintain a constant body temperature at all times. It would be harder for mammals to maintain their normal temperatures at 10 degrees Celsius, meaning that their respiration rates would go up as more energy would be required to maintain their normal temperatures.

Q10 = (R2/R1)

(10/T2-T1)

Germinating Peas

T1=10 degrees Celsius

T2=25 degrees Celsius

R1=0.014 mL of O2/min

R2=0.006 mL of O2/min

Q10=(0.014/0.006)

(10/25-10)=1.76

Dry Peas

T1=10 degrees Celsius

T2=25 degrees Celsius

R1=0.002 mL of O2/min

R2=0.002 mL of O2/min

Q10=(0.002/0.002)

(10/25-10)=1

For Germinating Peas, the Q10 was 1.76, which is close to 2. Like most other human biological processes, respiration rate was temperature dependent. However, Dry Peas had a Q10 of 1, meaning that the temperature did not have a large effect on the respiration rate, supporting that Dry Peas are temperature independent. Although the raw data showed some changes for Dry Peas as the temperature decreased, the Dry Peas were overall temperature independent.