Biology – Respiration | e-Consult

A simple respirometer investigates respiration by measuring the volume of carbon dioxide (CO₂) produced by a biological sample. Here's a description of how it can be used to study the effect of temperature on the rate of respiration in yeast:

Apparatus Required:

• Two identical bottles or containers
• Yeast solution (e.g., 5% glucose solution with yeast)
• Rubber stoppers with a hole for a gas collection tube
• Gas collection tubes (inverted over a water-filled trough)
• Thermometer
• Water bath (capable of maintaining different temperatures)
• Measuring cylinder (e.g., 50 cm³)
• Stopwatch
• Distilled water

Experimental Procedure:

1. Prepare the yeast solution according to a standard protocol.
2. Add a fixed volume of the yeast solution to each of the two bottles.
3. Insert a gas collection tube into the bottle, ensuring it is inverted over a trough of water.
4. Place one bottle in a water bath set to a specific temperature (e.g., 20°C).
5. Place the other bottle in a water bath set to a different temperature (e.g., 30°C).
6. Allow the experiment to run for a set period (e.g., 10 minutes).
7. Measure the volume of CO₂ collected in each gas collection tube using the water displacement method. This can be done by measuring the volume of water displaced in the trough.
8. Repeat the experiment at least three times for each temperature to obtain reliable data.

Determining the Rate of Respiration:

The rate of respiration is determined by measuring the volume of CO₂ produced per unit time (e.g., mL CO₂ / minute). This is calculated by dividing the volume of CO₂ collected by the duration of the experiment. The rate of respiration is then plotted against the temperature to show the effect of temperature on the rate.