Investigating the rate of respiration in organisms
Yeast Respiration
Materials:
Glucose solution (5%)
Dried yeast suspension (10%)
Side-arm boiling tube or conical flask
Beaker
Gas syringe or delivery tube
Stopwatch
Procedure:
Prepare a 5% glucose solution and a 10% suspension of dried yeast.
Place 5 cm^3 of the glucose solution and 1 cm^3 of the yeast suspension in a side-arm boiling tube or conical flask. Adjust volumes accordingly if using a conical flask.
Place the container with the yeast and glucose in a beaker of water at 20°C.
Allow the yeast to adjust to the temperature of the water in the beaker for a few minutes.
Attach the side arm to a gas syringe, ensuring the plunger is pushed fully in.
Start the stopwatch and allow the gas produced by yeast to collect in the gas syringe for a fixed time.
Record the time and the volume of gas produced.
Repeat the experiment for a range of different temperatures.
Calculate the gas production per minute for each temperature.
Note: If a gas syringe is unavailable, attach the side arm to a delivery tube inserted into a boiling tube containing water. Count the bubbles produced for a fixed time.
Results:
The volume of gas produced increases as the temperature is increased to 35 or 40°C.
Higher temperatures slow down the rate of gas production.
Low temperatures may result in less gas being produced.
