### Introduction

Cellular respiration refers to the process of converting the chemical energy of organic molecules into a form immediately usable by organisms. Glucose may be oxidized completely if sufficient oxygen is available and is summarized by the following reaction:

${{\text{C}}_{\text{6}}}{{\text{H}}_{{\text{12}}}}{{\text{O}}_{\text{6}}}{\text{ + 6 }}{{\text{O}}_{\text{2}}}{\text{(g)}} \leftrightarrow {\text{6 }}{{\text{H}}_{\text{2}}}{\text{O + 6 C}}{{\text{O}}_{\text{2}}}{\text{(g) + energy}}$

All organisms, including plants and animals, oxidize glucose for energy. Often, this energy is used to convert ADP and phosphate into ATP.

To measure the rate of cellular respiration, the pressure change due to the consumption of oxygen by peas will be measured with a Gas Pressure Sensor. It is not possible to directly measure pressure changes due to oxygen, since the Gas Pressure Sensor measures the total pressure change. Carbon dioxide is produced as oxygen is consumed. The pressure due to CO2 might cancel out any change due to the consumption of oxygen. To eliminate this problem, a chemical will be added that will selectively remove CO2. Potassium hydroxide, KOH, will chemically react with CO2 by the following equation:

${\text{2 KOH + C}}{{\text{O}}_{\text{2}}} \to {{\text{K}}_{\text{2}}}{\text{C}}{{\text{O}}_{\text{3}}}{\text{ + }}{{\text{H}}_{\text{2}}}{\text{O}}$

This will allow you to monitor pressure changes exclusively due to the consumption of oxygen.

A respirometer is the system used to measure cellular respiration. Pressure changes in the respirometer are directly proportional to a change in the amount of gas in the respirometer, providing the volume and the temperature of the respirometer do not change. If you wish to compare the consumption of oxygen in two different respirometers, as we will in this experiment, you must keep the volume and temperature of the air equal in each respirometer.

Both germinating and non-germinating peas will be tested. Additionally, cellular respiration of germinating peas at two different temperatures will be tested.

### Objectives

In this experiment, you will

• Measure gas production.
• Study the effect of temperature on cell respiration.
• Determine whether germinating peas and non-germinating peas respire.
• Compare the rates of cell respiration in germinating and non-germinating peas.